From 1c273f96f86ea0d9058db57a5fa16eb2f3034711 Mon Sep 17 00:00:00 2001
From: Kailash Turimella <kailash.turimella@gmail.com>
Date: Mon, 6 Oct 2025 14:46:50 -0700
Subject: [PATCH 1/5] completed

---
 Makefile             |   2 +
 docs/compress.md     |  50 ++++++++++++
 mkfs/mkfs.c          | 103 +++++++++++++++++++++++--
 user/compress.c      | 178 +++++++++++++++++++++++++++++++++++++++++++
 user/compress_test.c | 130 +++++++++++++++++++++++++++++++
 5 files changed, 455 insertions(+), 8 deletions(-)
 create mode 100644 docs/compress.md
 create mode 100644 user/compress.c
 create mode 100644 user/compress_test.c

diff --git a/Makefile b/Makefile
index cf031b0..477d25f 100644
--- a/Makefile
+++ b/Makefile
@@ -124,6 +124,8 @@ mkfs/mkfs: mkfs/mkfs.c $K/fs.h $K/param.h
 
 UPROGS=\
 	$U/_cat\
+	$U/_compress\
+	$U/_compress_test\
 	$U/_echo\
 	$U/_forktest\
 	$U/_grep\
diff --git a/docs/compress.md b/docs/compress.md
new file mode 100644
index 0000000..c2cae4d
--- /dev/null
+++ b/docs/compress.md
@@ -0,0 +1,50 @@
+# compress — Run-Length Encode / Decode files
+
+## Usage
+
+`compress` provides simple Run-Length Encoding (RLE) for any file. It can read from **stdin** and write to **stdout** if file paths are omitted.
+
+* `-c` : **Compress** input → RLE output
+* `-d` : **Decompress** RLE input → original bytes
+* `-h` : Show help/usage
+
+> RLE format: a stream of 2-byte pairs `[count][value]` with `count` in 1–255. Long runs are split. Random data may grow in size.
+
+### Examples
+
+```sh
+# File → file
+$ compress -c README.md README.rle
+$ compress -d README.rle README.out
+
+# Stream mode (stdin/stdout + pipes/redirection)
+$ cat README.md | compress -c > foo.rle
+$ cat foo.rle    | compress -d > out.txt
+```
+
+---
+
+## Testing
+
+An automated test runner `/compress_test` is included. It creates sample files, runs compress/decompress, and checks round-trip equality.
+
+### To run tests
+
+1. Boot the OS and open the shell.
+2. Run:
+
+   ```
+   /compress_test
+   ```
+3. You should see `PASS`/`FAIL` lines and a summary, e.g.:
+
+   ```
+   [PASS] small text
+   [PASS] empty file
+   [PASS] long run 1000x'A'
+   [PASS] binary 0x00..0xFF
+
+   All tests PASSED 
+   ```
+
+If a test fails, the message indicates which stage (compress/decompress/compare) had an issue.
diff --git a/mkfs/mkfs.c b/mkfs/mkfs.c
index 5f080bc..5e3873e 100644
--- a/mkfs/mkfs.c
+++ b/mkfs/mkfs.c
@@ -4,12 +4,18 @@
 #include <string.h>
 #include <fcntl.h>
 #include <assert.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <sys/stat.h>
 
+#define dirent xv6_dirent
 #define stat xv6_stat  // avoid clash with host struct stat
 #include "kernel/types.h"
 #include "kernel/fs.h"
 #include "kernel/stat.h"
 #include "kernel/param.h"
+#undef dirent
+#undef stat
 
 #ifndef static_assert
 #define static_assert(a, b) do { switch (0) case 0: case (a): ; } while (0)
@@ -20,9 +26,9 @@
 // Disk layout:
 // [ boot block | sb block | log | inode blocks | free bit map | data blocks ]
 
-int nbitmap = FSSIZE/BPB + 1;
+int nbitmap = FSSIZE/(BSIZE*8) + 1;
 int ninodeblocks = NINODES / IPB + 1;
-int nlog = LOGBLOCKS+1;   // Header followed by LOGBLOCKS data blocks.
+int nlog = LOGBLOCKS;
 int nmeta;    // Number of meta blocks (boot, sb, nlog, inode, bitmap)
 int nblocks;  // Number of data blocks
 
@@ -65,12 +71,88 @@ xint(uint x)
   return y;
 }
 
+void
+add_file(int parent_fd, uint parentino, char *filename)
+{
+  uint inum;
+  int fd;
+  char buf[BSIZE];
+  struct xv6_dirent de;
+
+  if((fd = openat(parent_fd, filename, 0)) < 0)
+    die(filename);
+
+  inum = ialloc(T_FILE);
+
+  bzero(&de, sizeof(de));
+  de.inum = xshort(inum);
+  strncpy(de.name, filename, DIRSIZ);
+  iappend(parentino, &de, sizeof(de));
+
+  ssize_t cc;
+  while((cc = read(fd, buf, sizeof(buf))) > 0)
+    iappend(inum, buf, cc);
+
+  close(fd);
+}
+
+uint
+add_dir(int level, int parent_fd, uint parentino, char *dirname)
+{
+  struct xv6_dirent de;
+  uint dino = ialloc(T_DIR);
+  bzero(&de, sizeof(de));
+  de.inum = xshort(dino);
+  strcpy(de.name, dirname);
+  iappend(parentino, &de, sizeof(de));
+
+  bzero(&de, sizeof(de));
+  de.inum = xshort(dino);
+  strcpy(de.name, ".");
+  iappend(dino, &de, sizeof(de));
+
+  bzero(&de, sizeof(de));
+  de.inum = xshort(parentino);
+  strcpy(de.name, "..");
+  iappend(dino, &de, sizeof(de));
+
+  int dir_fd = -1;
+  if ((dir_fd = openat(parent_fd, dirname, O_RDONLY)) == -1) {
+    perror("open");
+    return dino;
+  }
+
+  DIR *d = fdopendir(dir_fd);
+  if (d == NULL) {
+    perror("fdopendir");
+    return dino;
+  }
+
+  struct dirent *e;
+  while ((e = readdir(d)) != NULL) {
+    if (e->d_name[0] == '.') {
+      continue;
+    }
+
+    if (e->d_type == DT_REG) {
+      printf("%*s+ %s\n", level * 2, "", e->d_name);
+      add_file(dir_fd, dino, e->d_name);
+    } else if (e->d_type == DT_DIR) {
+      printf("%*s+ /%s\n", level * 2, "", e->d_name);
+      add_dir(level + 1, dir_fd, dino, e->d_name);
+    }
+  }
+  close(dir_fd);
+
+  return dino;
+}
+
 int
 main(int argc, char *argv[])
 {
   int i, cc, fd;
   uint rootino, inum, off;
-  struct dirent de;
+  struct xv6_dirent de;
   char buf[BSIZE];
   struct dinode din;
 
@@ -83,7 +165,7 @@ main(int argc, char *argv[])
   }
 
   assert((BSIZE % sizeof(struct dinode)) == 0);
-  assert((BSIZE % sizeof(struct dirent)) == 0);
+  assert((BSIZE % sizeof(struct xv6_dirent)) == 0);
 
   fsfd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666);
   if(fsfd < 0)
@@ -102,7 +184,7 @@ main(int argc, char *argv[])
   sb.inodestart = xint(2+nlog);
   sb.bmapstart = xint(2+nlog+ninodeblocks);
 
-  printf("nmeta %d (boot, super, log blocks %u, inode blocks %u, bitmap blocks %u) blocks %d total %d\n",
+  printf("nmeta %d (boot, super, log blocks %u inode blocks %u, bitmap blocks %u) blocks %d total %d\n",
          nmeta, nlog, ninodeblocks, nbitmap, nblocks, FSSIZE);
 
   freeblock = nmeta;     // the first free block that we can allocate
@@ -128,6 +210,13 @@ main(int argc, char *argv[])
   iappend(rootino, &de, sizeof(de));
 
   for(i = 2; i < argc; i++){
+    struct stat sb;
+    stat(argv[i], &sb);
+    if (S_ISDIR(sb.st_mode)) {
+      add_dir(0, AT_FDCWD, rootino, argv[i]);
+      continue;
+    }
+
     // get rid of "user/"
     char *shortname;
     if(strncmp(argv[i], "user/", 5) == 0)
@@ -147,8 +236,6 @@ main(int argc, char *argv[])
     if(shortname[0] == '_')
       shortname += 1;
 
-    assert(strlen(shortname) <= DIRSIZ);
-    
     inum = ialloc(T_FILE);
 
     bzero(&de, sizeof(de));
@@ -240,7 +327,7 @@ balloc(int used)
   int i;
 
   printf("balloc: first %d blocks have been allocated\n", used);
-  assert(used < BPB);
+  assert(used < BSIZE*8);
   bzero(buf, BSIZE);
   for(i = 0; i < used; i++){
     buf[i/8] = buf[i/8] | (0x1 << (i%8));
diff --git a/user/compress.c b/user/compress.c
new file mode 100644
index 0000000..ee64323
--- /dev/null
+++ b/user/compress.c
@@ -0,0 +1,178 @@
+// user/compress.c — Run-Length Encoding (RLE) compressor/decompressor for FogOSv2
+// Format: stream of pairs [count:1 byte][value:1 byte], repeated to EOF.
+// Runs >255 are split into multiple pairs.
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "kernel/fcntl.h"
+#include "user/user.h"
+
+#define INBUF  512
+#define OUTBUF 128
+
+static void usage(void) {
+  printf(
+    "usage:\n"
+    "  compress -c [in] [out]   # compress\n"
+    "  compress -d [in] [out]   # decompress\n"
+    "If in/out omitted, stdin/stdout are used.\n"
+  );
+}
+
+static int open_in(const char *p) {
+  if (!p) return 0; // stdin
+  int fd = open(p, O_RDONLY);
+  if (fd < 0) {
+    printf("compress: cannot open %s\n", p);
+  }
+  return fd;
+}
+
+static int open_out(const char *p) {
+  if (!p) return 1; // stdout
+  int fd = open(p, O_CREATE | O_WRONLY);
+  if (fd < 0) {
+    printf("compress: cannot create %s\n", p);
+  }
+  return fd;
+}
+
+/* -------------------- RLE compress -------------------- */
+static int rle_compress_fd(int in, int out) {
+  uchar buf[INBUF];
+  int have_prev = 0;
+  uchar prev = 0;
+  int cnt = 0;
+
+  for (;;) {
+    int n = read(in, buf, sizeof(buf));
+    if (n < 0) { printf("compress: read error\n"); return -1; }
+    if (n == 0) break;
+
+    for (int i = 0; i < n; i++) {
+      uchar b = buf[i];
+      if (!have_prev) {
+        prev = b; cnt = 1; have_prev = 1;
+      } else if (b == prev && cnt < 255) {
+        cnt++;
+      } else {
+        uchar pair[2] = { (uchar)cnt, prev };
+        if (write(out, pair, 2) != 2) { printf("compress: write error\n"); return -1; }
+        prev = b; cnt = 1;
+      }
+    }
+  }
+
+  if (have_prev) {
+    uchar pair[2] = { (uchar)cnt, prev };
+    if (write(out, pair, 2) != 2) { printf("compress: write error\n"); return -1; }
+  }
+  return 0;
+}
+
+/* ------------------ RLE decompress -------------------- */
+static int rle_decompress_fd(int in, int out) {
+  uchar buf[INBUF];
+  int carry = -1;      // -1 = no carry; otherwise holds a pending count byte
+  uchar outbuf[OUTBUF];
+
+  for (int k = 0; k < OUTBUF; k++) outbuf[k] = 0; // init once
+
+  for (;;) {
+    int n = read(in, buf, sizeof(buf));
+    if (n < 0) { printf("compress: read error\n"); return -1; }
+    if (n == 0) break;
+
+    int i = 0;
+
+    // If we had an odd byte (count) from the previous read, pair it now.
+    if (carry != -1) {
+      if (n < 1) { printf("compress: corrupt input (missing value)\n"); return -1; }
+      int cnt = carry;
+      uchar val = buf[0];
+      if (cnt <= 0) { printf("compress: corrupt input (zero/neg count)\n"); return -1; }
+
+      // emit cnt copies of val
+      for (int j = 0; j < OUTBUF; j++) outbuf[j] = val;
+      int left = cnt;
+      while (left > 0) {
+        int chunk = left < OUTBUF ? left : OUTBUF;
+        if (write(out, outbuf, chunk) != chunk) { printf("compress: write error\n"); return -1; }
+        left -= chunk;
+      }
+      i = 1;       // consumed one byte (value)
+      carry = -1;  // cleared
+    }
+
+    // Process full pairs from this buffer
+    for (; i + 1 < n; i += 2) {
+      int cnt = buf[i];
+      uchar val = buf[i+1];
+      if (cnt <= 0) { printf("compress: corrupt input (zero/neg count)\n"); return -1; }
+
+      for (int j = 0; j < OUTBUF; j++) outbuf[j] = val;
+      int left = cnt;
+      while (left > 0) {
+        int chunk = left < OUTBUF ? left : OUTBUF;
+        if (write(out, outbuf, chunk) != chunk) { printf("compress: write error\n"); return -1; }
+        left -= chunk;
+      }
+    }
+
+    // If there's one byte left, it's a dangling count; carry it to next read
+    if (i < n) {
+      carry = buf[n-1];
+    }
+  }
+
+  if (carry != -1) { // ended with odd number of bytes → corrupt
+    printf("compress: corrupt input (odd byte count)\n");
+    return -1;
+  }
+  return 0;
+}
+
+/* ------------------------ main ------------------------ */
+int main(int argc, char *argv[]) {
+  if (argc < 2) { usage(); exit(1); }
+
+  int mode = 0;             // 1 = compress, 2 = decompress
+  const char *inpath = 0;   // NULL -> stdin
+  const char *outpath = 0;  // NULL -> stdout
+
+  // Parse: first flag (-c/-d), then up to 2 positional args
+  for (int i = 1; i < argc; i++) {
+    char *a = argv[i];
+    if (strcmp(a, "-c") == 0) {
+      mode = 1;
+    } else if (strcmp(a, "-d") == 0) {
+      mode = 2;
+    } else if (!inpath) {
+      inpath = a;
+    } else if (!outpath) {
+      outpath = a;
+    } else {
+      printf("compress: too many arguments\n");
+      usage();
+      exit(1);
+    }
+  }
+
+  if (mode == 0) {
+    printf("compress: must specify -c or -d\n");
+    usage();
+    exit(1);
+  }
+
+  int in = open_in(inpath);
+  if (in < 0) exit(1);
+  int out = open_out(outpath);
+  if (out < 0) { if (in > 1) close(in); exit(1); }
+
+  int rc = (mode == 1) ? rle_compress_fd(in, out) : rle_decompress_fd(in, out);
+
+  if (in > 1) close(in);
+  if (out > 1) close(out);
+  if (rc < 0) exit(1);
+  exit(0);
+}
diff --git a/user/compress_test.c b/user/compress_test.c
new file mode 100644
index 0000000..f4b4b6f
--- /dev/null
+++ b/user/compress_test.c
@@ -0,0 +1,130 @@
+// It creates small input files, runs `compress -c` then `compress -d` via
+// fork/exec, and verifies the round-trip output matches the original.
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "kernel/fcntl.h"
+#include "user/user.h"
+
+#define IN_CHUNK 512
+
+static int write_file(const char *path, const void *buf, int len) {
+  int fd = open(path, O_CREATE | O_WRONLY);
+  if (fd < 0) { printf("compress_test: open(O_CREATE) %s failed\n", path); return -1; }
+  const char *p = (const char*)buf;
+  int left = len;
+  while (left > 0) {
+    int n = write(fd, p, left);
+    if (n < 0) { printf("compress_test: write %s failed\n", path); close(fd); return -1; }
+    left -= n; p += n;
+  }
+  close(fd);
+  return 0;
+}
+
+static int files_equal(const char *a, const char *b) {
+  int fa = open(a, O_RDONLY);
+  int fb = open(b, O_RDONLY);
+  if (fa < 0 || fb < 0) { if (fa>=0) close(fa); if (fb>=0) close(fb); return 0; }
+
+  char ba[IN_CHUNK], bb[IN_CHUNK];
+  for (;;) {
+    int na = read(fa, ba, sizeof(ba));
+    int nb = read(fb, bb, sizeof(bb));
+    if (na < 0 || nb < 0) { close(fa); close(fb); return 0; }
+    if (na != nb) { close(fa); close(fb); return 0; }
+    if (na == 0) { close(fa); close(fb); return 1; } // both EOF
+    for (int i = 0; i < na; i++) if (ba[i] != bb[i]) { close(fa); close(fb); return 0; }
+  }
+}
+
+static int run_prog(char *prog, char *argv[]) {
+  int pid = fork();
+  if (pid < 0) { printf("compress_test: fork failed\n"); return -1; }
+  if (pid == 0) {
+    // child
+    exec(prog, argv);
+    printf("compress_test: exec %s failed\n", prog);
+    exit(127);
+  }
+  int status = 0;
+  if (wait(&status) < 0) {
+    // Some FogOS variants support wait(&status); others allow wait(0).
+    // If your toolchain complains, change to: wait(0);
+  }
+  return status;
+}
+
+static int do_roundtrip(const char *label, const char *infile,
+                        const char *rlefile, const char *outfile)
+{
+  // compress -c infile rlefile
+  char *argv_c[] = { "compress", "-c", (char*)infile, (char*)rlefile, 0 };
+  int st1 = run_prog("compress", argv_c);
+  if (st1 != 0) { printf("[FAIL] %s: compress step failed (status=%d)\n", label, st1); return -1; }
+
+  // decompress -d rlefile outfile
+  char *argv_d[] = { "compress", "-d", (char*)rlefile, (char*)outfile, 0 };
+  int st2 = run_prog("compress", argv_d);
+  if (st2 != 0) { printf("[FAIL] %s: decompress step failed (status=%d)\n", label, st2); return -1; }
+
+  // compare
+  if (!files_equal(infile, outfile)) {
+    printf("[FAIL] %s: round-trip mismatch\n", label);
+    return -1;
+  }
+
+  printf("[PASS] %s\n", label);
+  return 0;
+}
+
+static void make_repeating(char *buf, int len, char byte) {
+  for (int i = 0; i < len; i++) buf[i] = byte;
+}
+
+int
+main(void)
+{
+  int rc = 0;
+
+  // --- Test 1: small text ---
+  const char *t1_in  = "t1_in.txt";
+  const char *t1_rle = "t1.rle";
+  const char *t1_out = "t1_out.txt";
+  const char *msg = "Hello RLE!\nHello RLE!\nAAABBBCCCDDD\n";
+  if (write_file(t1_in, msg, strlen(msg)) < 0) rc = -1;
+  if (rc == 0 && do_roundtrip("small text", t1_in, t1_rle, t1_out) < 0) rc = -1;
+
+  // --- Test 2: empty file ---
+  const char *t2_in  = "t2_in.bin";
+  const char *t2_rle = "t2.rle";
+  const char *t2_out = "t2_out.bin";
+  if (rc == 0 && write_file(t2_in, "", 0) < 0) rc = -1;
+  if (rc == 0 && do_roundtrip("empty file", t2_in, t2_rle, t2_out) < 0) rc = -1;
+
+  // --- Test 3: long run (>255) ---
+  const char *t3_in  = "t3_in.bin";
+  const char *t3_rle = "t3.rle";
+  const char *t3_out = "t3_out.bin";
+  char big[1000];
+  make_repeating(big, sizeof(big), 'A');
+  if (rc == 0 && write_file(t3_in, big, sizeof(big)) < 0) rc = -1;
+  if (rc == 0 && do_roundtrip("long run 1000x'A'", t3_in, t3_rle, t3_out) < 0) rc = -1;
+
+  // --- Test 4: binary with zero bytes ---
+  const char *t4_in  = "t4_in.bin";
+  const char *t4_rle = "t4.rle";
+  const char *t4_out = "t4_out.bin";
+  char bin[256];
+  for (int i = 0; i < 256; i++) bin[i] = (char)i;       // 0x00..0xFF once
+  if (rc == 0 && write_file(t4_in, bin, sizeof(bin)) < 0) rc = -1;
+  if (rc == 0 && do_roundtrip("binary 0x00..0xFF", t4_in, t4_rle, t4_out) < 0) rc = -1;
+
+  if (rc == 0) {
+    printf("\nAll tests PASSED\n");
+    exit(0);
+  } else {
+    printf("\nSome tests FAILED\n");
+    exit(1);
+  }
+}

From 7e31681dd90e93ad4d1af7d89b181658c7012472 Mon Sep 17 00:00:00 2001
From: Kailash Turimella <kailash.turimella@gmail.com>
Date: Tue, 30 Dec 2025 08:32:50 +0530
Subject: [PATCH 2/5] p

---
 1.sh               |  33 ++++
 2.sh               | 433 +++++++++++++++++++++++++++++++++++++++++++++
 3.sh               | 430 ++++++++++++++++++++++++++++++++++++++++++++
 4.sh               | 432 ++++++++++++++++++++++++++++++++++++++++++++
 Makefile           |  34 +++-
 kernel/exec.c      |  35 ++++
 kernel/fs.c        |  93 ++++++++++
 kernel/memlayout.h |   6 +
 kernel/proc.c      | 183 +++++++++++++++----
 kernel/proc.h      |   8 +
 kernel/strace.h    | 121 +++++++++++++
 kernel/syscall.c   |  28 ++-
 kernel/syscall.h   |   9 +
 kernel/sysfile.c   |  28 +++
 kernel/sysproc.c   | 104 ++++++++++-
 mkfs/mkfs.c        | 105 +----------
 user/sh.c          |  34 +++-
 user/user.h        |  47 +++--
 user/usys.pl       |   9 +
 19 files changed, 2016 insertions(+), 156 deletions(-)
 create mode 100644 1.sh
 create mode 100644 2.sh
 create mode 100644 3.sh
 create mode 100644 4.sh
 create mode 100644 kernel/strace.h

diff --git a/1.sh b/1.sh
new file mode 100644
index 0000000..3c124d2
--- /dev/null
+++ b/1.sh
@@ -0,0 +1,33 @@
+# Start of file. This line should not cause errors
+echo Command 000
+echo Command 001
+echo Command 002
+ehchhho Command 003
+echo Command 004
+echo Command 005
+echo Command 006 # Look, it's command 6. This shouldn't print
+echo Command 007
+echo Command 008
+# Empty commands (like this one) and blank lines should not go in history
+
+
+
+
+
+/ls /
+mkdir a
+mkdir a/b
+mkdir a/b/c
+mkdir a/b/c/hello
+cd a
+cd b/c/hello
+/ls
+/wc /README.md
+cd /
+/wc README.md
+echo ---
+history
+echo ---
+history -t
+exit
+echo If you see this line, exit is not working.
diff --git a/2.sh b/2.sh
new file mode 100644
index 0000000..d07fb12
--- /dev/null
+++ b/2.sh
@@ -0,0 +1,433 @@
+# Make sure empty lines (including this one) are handled
+# properly to pass this test.
+#
+# Bad/unknown commands **do** go into the history.
+
+thisisacommandthatprobablydoesntexistbutletstryitanywayhuh
+echo Command 000
+echo Command 001
+echo Command 002
+echo Command 003
+echo Command 004
+echo Command 005
+
+echo Command 006
+
+echo Command 007
+
+echo Command 008
+
+echo Command 009
+echo Command 010
+echo Command 011
+echo Command 012
+echo Command 013
+echo Command 014
+echo Command 015
+echo Command 016
+echo Command 017
+echo Command 018
+echo Command 019
+echo Command 020
+echo Command 021
+echo Command 022
+echo Command 023
+echo Command 024
+echo Command 025
+echo Command 026
+echo Command 027
+echo Command 028
+echo Command 029
+echo Command 030
+echo Command 031
+echo Command 032
+echo Command 033
+echo Command 034
+echo Command 035
+echo Command 036
+echo Command 037
+echo Command 038
+echo Command 039
+echo Command 040
+echo Command 041
+echo Command 042
+echo Command 043
+echo Command 044
+echo Command 045
+echo Command 046
+echo Command 047
+echo Command 048
+echo Command 049
+echo Command 050
+echo Command 051
+echo Command 052
+echo Command 053
+echo Command 054
+echo Command 055
+echo Command 056
+echo Command 057
+echo Command 058
+echo Command 059
+echo Command 060
+echo Command 061
+echo Command 062
+echo Command 063
+echo Command 064
+echo Command 065
+echo Command 066
+echo Command 067
+echo Command 068
+echo Command 069
+echo Command 070
+echo Command 071
+echo Command 072
+echo Command 073
+echo Command 074
+echo Command 075
+echo Command 076
+echo Command 077
+echo Command 078
+echo Command 079
+echo Command 080
+echo Command 081
+echo Command 082
+echo Command 083
+echo Command 084
+echo Command 085
+echo Command 086
+echo Command 087
+echo Command 088
+echo Command 089
+echo Command 090
+echo Command 091
+echo Command 092
+echo Command 093
+echo Command 094
+echo Command 095
+echo Command 096
+echo Command 097
+echo Command 098
+echo Command 099
+echo Command 100
+echo Command 101
+echo Command 102
+echo Command 103
+echo Command 104
+echo Command 105
+echo Command 106
+echo Command 107
+echo Command 108
+echo Command 109
+echo Command 110
+echo Command 111
+echo Command 112
+echo Command 113
+echo Command 114
+echo Command 115
+echo Command 116
+echo Command 117
+echo Command 118
+echo Command 119
+echo Command 120
+echo Command 121
+echo Command 122
+echo Command 123
+echo Command 124
+echo Command 125
+echo Command 126
+echo Command 127
+echo Command 128
+echo Command 129
+echo Command 130
+echo Command 131
+echo Command 132
+echo Command 133
+echo Command 134
+echo Command 135
+echo Command 136
+echo Command 137
+echo Command 138
+echo Command 139
+echo Command 140
+echo Command 141
+echo Command 142
+echo Command 143
+echo Command 144
+echo Command 145
+echo Command 146
+echo Command 147
+echo Command 148
+echo Command 149
+echo Command 150
+echo Command 151
+echo Command 152
+echo Command 153
+echo Command 154
+echo Command 155
+echo Command 156
+echo Command 157
+echo Command 158
+echo Command 159
+echo Command 160
+echo Command 161
+echo Command 162
+echo Command 163
+echo Command 164
+echo Command 165
+echo Command 166
+echo Command 167
+echo Command 168
+echo Command 169
+echo Command 170
+echo Command 171
+echo Command 172
+echo Command 173
+echo Command 174
+echo Command 175
+echo Command 176
+echo Command 177
+echo Command 178
+echo Command 179
+echo Command 180
+echo Command 181
+echo Command 182
+echo Command 183
+echo Command 184
+echo Command 185
+echo Command 186
+echo Command 187
+echo Command 188
+echo Command 189
+echo Command 190
+echo Command 191
+echo Command 192
+echo Command 193
+echo Command 194
+echo Command 195
+echo Command 196
+echo Command 197
+echo Command 198
+echo Command 199
+echo Command 200
+echo Command 201
+echo Command 202
+echo Command 203
+echo Command 204
+echo Command 205
+echo Command 206
+echo Command 207
+echo Command 208
+echo Command 209
+echo Command 210
+echo Command 211
+echo Command 212
+echo Command 213
+echo Command 214
+echo Command 215
+echo Command 216
+echo Command 217
+echo Command 218
+echo Command 219
+echo Command 220
+echo Command 221
+echo Command 222
+echo Command 223
+echo Command 224
+echo Command 225
+echo Command 226
+echo Command 227
+echo Command 228
+echo Command 229
+echo Command 230
+echo Command 231
+echo Command 232
+echo Command 233
+echo Command 234
+echo Command 235
+echo Command 236
+echo Command 237
+echo Command 238
+echo Command 239
+echo Command 240
+echo Command 241
+echo Command 242
+echo Command 243
+echo Command 244
+echo Command 245
+echo Command 246
+echo Command 247
+echo Command 248
+echo Command 249
+echo Command 250
+echo Command 251
+echo Command 252
+echo Command 253
+echo Command 254
+echo Command 255
+echo Command 256
+echo Command 257
+echo Command 258
+echo Command 259
+echo Command 260
+echo Command 261
+echo Command 262
+echo Command 263
+echo Command 264
+echo Command 265
+echo Command 266
+echo Command 267
+echo Command 268
+echo Command 269
+echo Command 270
+echo Command 271
+echo Command 272
+echo Command 273
+echo Command 274
+echo Command 275
+echo Command 276
+echo Command 277
+echo Command 278
+echo Command 279
+echo Command 280
+echo Command 281
+echo Command 282
+echo Command 283
+echo Command 284
+echo Command 285
+echo Command 286
+echo Command 287
+echo Command 288
+echo Command 289
+echo Command 290
+echo Command 291
+echo Command 292
+echo Command 293
+echo Command 294
+echo Command 295
+echo Command 296
+echo Command 297
+echo Command 298
+echo Command 299
+echo Command 300
+echo Command 301
+echo Command 302
+echo Command 303
+echo Command 304
+echo Command 305
+echo Command 306
+echo Command 307
+echo Command 308
+echo Command 309
+echo Command 310
+echo Command 311
+echo Command 312
+echo Command 313
+echo Command 314
+echo Command 315
+echo Command 316
+echo Command 317
+echo Command 318
+echo Command 319
+echo Command 320
+echo Command 321
+echo Command 322
+echo Command 323
+echo Command 324
+echo Command 325
+echo Command 326
+echo Command 327
+echo Command 328
+echo Command 329
+echo Command 330
+echo Command 331
+echo Command 332
+echo Command 333
+echo Command 334
+echo Command 335
+echo Command 336
+echo Command 337
+echo Command 338
+echo Command 339
+echo Command 340
+echo Command 341
+echo Command 342
+echo Command 343
+echo Command 344
+echo Command 345
+echo Command 346
+echo Command 347
+echo Command 348
+echo Command 349
+echo Command 350
+echo Command 351
+echo Command 352
+echo Command 353
+echo Command 354
+echo Command 355
+echo Command 356
+echo Command 357
+echo Command 358
+echo Command 359
+echo Command 360
+echo Command 361
+echo Command 362
+echo Command 363
+echo Command 364
+echo Command 365
+echo Command 366
+echo Command 367
+echo Command 368
+echo Command 369
+echo Command 370
+echo Command 371
+echo Command 372
+echo Command 373
+echo Command 374
+echo Command 375
+echo Command 376
+echo Command 377
+echo Command 378
+echo Command 379
+echo Command 380
+echo Command 381
+echo Command 382
+echo Command 383
+echo Command 384
+echo Command 385
+echo Command 386
+echo Command 387
+echo Command 388
+echo Command 389
+echo Command 390
+echo Command 391
+echo Command 392
+echo Command 393
+echo Command 394
+echo Command 395
+echo Command 396
+echo Command 397
+echo Command 398
+echo Command 399
+echo Command 400
+echo Command 401
+echo Command 402
+echo Command 403
+echo Command 404
+echo Command 405
+echo Command 406
+pwd # May or may not exist...
+echo Command 407
+echo Command 408
+echo Command 409
+echo Command 410
+echo Command 411
+echo Command 412
+echo Command 413
+echo Command 414
+echo Command 415
+echo Command 416
+echo Command 417
+echo Command 418
+echo Command 419
+echo -----
+history
diff --git a/3.sh b/3.sh
new file mode 100644
index 0000000..6c4e8d8
--- /dev/null
+++ b/3.sh
@@ -0,0 +1,430 @@
+!542 # Doesn't actually exist :-)
+history
+echo Command 002
+echo Command 003
+echo Command 004
+echo Command 005
+echo Command 006
+echo Command 007
+echo Command 008
+echo Command 009
+echo Command 010
+echo Command 011
+echo Command 012
+echo Command 013
+echo Command 014
+echo Command 015
+echo Command 016
+echo Command 017
+echo Command 018
+echo Command 019
+echo Command 020
+echo Command 021
+echo Command 022
+echo Command 023
+echo Command 024
+echo Command 025
+echo Command 026
+echo Command 027
+echo Command 028
+echo Command 029
+echo Command 030
+echo Command 031
+echo Command 032
+echo Command 033
+echo Command 034
+echo Command 035
+echo Command 036
+echo Command 037
+echo Command 038
+echo Command 039
+echo Command 040
+echo Command 041
+echo Command 042
+echo Command 043
+echo Command 044
+echo Command 045
+echo Command 046
+echo Command 047
+echo Command 048
+echo Command 049
+echo Command 050
+echo Command 051
+echo Command 052
+echo Command 053
+echo Command 054
+echo Command 055
+echo Command 056
+echo Command 057
+echo Command 058
+echo Command 059
+echo Command 060
+echo Command 061
+echo Command 062
+echo Command 063
+echo Command 064
+echo Command 065
+echo Command 066
+echo Command 067
+echo Command 068
+echo Command 069
+echo Command 070
+echo Command 071
+echo Command 072
+echo Command 073
+echo Command 074
+echo Command 075
+echo Command 076
+echo Command 077
+echo Command 078
+echo Command 079
+echo Command 080
+echo Command 081
+echo Command 082
+echo Command 083
+echo Command 084
+echo Command 085
+echo Command 086
+echo Command 087
+echo Command 088
+echo Command 089
+echo Command 090
+echo Command 091
+echo Command 092
+echo Command 093
+echo Command 094
+echo Command 095
+echo Command 096
+echo Command 097
+echo Command 098
+echo Command 099
+echo Command 100
+echo Command 101
+echo Command 102
+echo Command 103
+echo Command 104
+echo Command 105
+echo Command 106
+echo Command 107
+echo Command 108
+echo Command 109
+echo Command 110
+echo Command 111
+echo Command 112
+echo Command 113
+echo Command 114
+echo Command 115
+echo Command 116
+echo Command 117
+echo Command 118
+echo Command 119
+echo Command 120
+echo Command 121
+echo Command 122
+echo Command 123
+echo Command 124
+echo Command 125
+echo Command 126
+echo Command 127
+echo Command 128
+echo Command 129
+echo Command 130
+echo Command 131
+echo Command 132
+echo Command 133
+echo Command 134
+echo Command 135
+echo Command 136
+echo Command 137
+echo Command 138
+echo Command 139
+echo Command 140
+echo Command 141
+echo Command 142
+echo Command 143
+echo Command 144
+echo Command 145
+echo Command 146
+echo Command 147
+echo Command 148
+echo Command 149
+echo Command 150
+echo Command 151
+echo Command 152
+echo Command 153
+echo Command 154
+echo Command 155
+echo Command 156
+echo Command 157
+echo Command 158
+echo Command 159
+echo Command 160
+echo Command 161
+echo Command 162
+echo Command 163
+echo Command 164
+echo Command 165
+echo Command 166
+echo Command 167
+echo Command 168
+echo Command 169
+echo Command 170
+echo Command 171
+echo Command 172
+echo Command 173
+echo Command 174
+echo Command 175
+echo Command 176
+echo Command 177
+echo Command 178
+echo Command 179
+echo Command 180
+echo Command 181
+echo Command 182
+echo Command 183
+echo Command 184
+echo Command 185
+echo Command 186
+echo Command 187
+echo Command 188
+echo Command 189
+echo Command 190
+echo Command 191
+echo Command 192
+echo Command 193
+echo Command 194
+echo Command 195
+echo Command 196
+echo Command 197
+echo Command 198
+echo Command 199
+echo Command 200
+echo Command 201
+echo Command 202
+echo Command 203
+echo Command 204
+echo Command 205
+echo Command 206
+echo Command 207
+echo Command 208
+echo Command 209
+echo Command 210
+echo Command 211
+echo Command 212
+echo Command 213
+echo Command 214
+echo Command 215
+echo Command 216
+echo Command 217
+echo Command 218
+echo Command 219
+echo Command 220
+echo Command 221
+echo Command 222
+echo Command 223
+echo Command 224
+echo Command 225
+echo Command 226
+echo Command 227
+echo Command 228
+echo Command 229
+echo Command 230
+echo Command 231
+echo Command 232
+echo Command 233
+echo Command 234
+echo Command 235
+echo Command 236
+echo Command 237
+echo Command 238
+echo Command 239
+echo Command 240
+echo Command 241
+echo Command 242
+echo Command 243
+echo Command 244
+echo Command 245
+echo Command 246
+echo Command 247
+echo Command 248
+echo Command 249
+echo Command 250
+echo Command 251
+echo Command 252
+echo Command 253
+echo Command 254
+echo Command 255
+echo Command 256
+echo Command 257
+echo Command 258
+echo Command 259
+echo Command 260
+echo Command 261
+echo Command 262
+echo Command 263
+echo Command 264
+echo Command 265
+echo Command 266
+echo Command 267
+echo Command 268
+echo Command 269
+echo Command 270
+echo Command 271
+echo Command 272
+echo Command 273
+echo Command 274
+echo Command 275
+echo Command 276
+echo Command 277
+echo Command 278
+echo Command 279
+echo Command 280
+echo Command 281
+echo Command 282
+echo Command 283
+echo Command 284
+echo Command 285
+echo Command 286
+echo Command 287
+echo Command 288
+echo Command 289
+echo Command 290
+echo Command 291
+echo Command 292
+echo Command 293
+echo Command 294
+echo Command 295
+echo Command 296
+echo Command 297
+echo Command 298
+echo Command 299
+echo Command 300
+echo Command 301
+echo Command 302
+echo Command 303
+echo Command 304
+echo Command 305
+echo Command 306
+echo Command 307
+echo Command 308
+echo Command 309
+echo Command 310
+echo Command 311
+echo Command 312
+echo Command 313
+echo Command 314
+echo Command 315
+echo Command 316
+echo Command 317
+echo Command 318
+echo Command 319
+echo Command 320
+echo Command 321
+echo Command 322
+echo Command 323
+echo Command 324
+echo Command 325
+echo Command 326
+echo Command 327
+echo Command 328
+echo Command 329
+echo Command 330
+echo Command 331
+echo Command 332
+echo Command 333
+echo Command 334
+echo Command 335
+echo Command 336
+echo Command 337
+echo Command 338
+echo Command 339
+echo Command 340
+echo Command 341
+echo Command 342
+echo Command 343
+echo Command 344
+echo Command 345
+echo Command 346
+echo Command 347
+echo Command 348
+echo Command 349
+echo Command 350
+echo Command 351
+echo Command 352
+echo Command 353
+echo Command 354
+echo Command 355
+echo Command 356
+echo Command 357
+echo Command 358
+echo Command 359
+echo Command 360
+echo Command 361
+echo Command 362
+echo Command 363
+echo Command 364
+echo Command 365
+echo Command 366
+echo Command 367
+echo Command 368
+echo Command 369
+echo Command 370
+echo Command 371
+echo Command 372
+echo Command 373
+echo Command 374
+echo Command 375
+echo Command 376
+echo Command 377
+echo Command 378
+echo Command 379
+echo Command 380
+echo Command 381
+echo Command 382
+echo Command 383
+echo Command 384
+echo Command 385
+echo Command 386
+echo Command 387
+echo Command 388
+echo Command 389
+echo Command 390
+echo Command 391
+echo Command 392
+echo Command 393
+echo Command 394
+echo Command 395
+echo Command 396
+echo Command 397
+echo Command 398
+echo Command 399
+echo Command 400
+echo Command 401
+echo Command 402
+echo Command 403
+echo Command 404
+echo Command 405
+echo Command 406
+echo Command 407
+echo Command 408
+echo Command 409
+echo Command 410
+echo Command 411
+echo Command 412
+echo Command 413
+echo Command 414
+echo Command 415
+echo Command 416
+echo Command 417
+echo Command 418
+echo Command 419
+echo Command 420
+echo -----
+history
+echo -----
+!420 # Works!
+!325 # Works!
+!325 # Shouldn't work the 2nd time -- gets popped off history.
+!401 		# Works!
+!23  # Does not exist anymore
+!999 # Hasn't happened yet
diff --git a/4.sh b/4.sh
new file mode 100644
index 0000000..22e012c
--- /dev/null
+++ b/4.sh
@@ -0,0 +1,432 @@
+echo Command 000
+echo Command 001
+cat /README.md
+echo Command 003
+echo Command 004
+echo Command 005
+echo Command 006
+echo Command 007
+echo Command 008
+echo Command 009
+echo Command 010
+echo Command 011
+echo Command 012
+echo Command 013
+echo Command 014
+echo Command 015
+echo Command 016
+echo Command 017
+echo Command 018
+echo Command 019
+echo Command 020
+echo Command 021
+echo Command 022
+echo Command 023
+echo Command 024
+echo Command 025
+echo Command 026
+echo Command 027
+echo Command 028
+echo Command 029
+echo Command 030
+echo Command 031
+echo Command 032
+echo Command 033
+echo Command 034
+echo Command 035
+echo Command 036
+echo Command 037
+echo Command 038
+echo Command 039
+echo Command 040
+echo Command 041
+echo Command 042
+echo Command 043
+echo Command 044
+echo Command 045
+echo Command 046
+echo Command 047
+echo Command 048
+echo Command 049
+echo Command 050
+echo Command 051
+echo Command 052
+echo Command 053
+echo Command 054
+echo Command 055
+echo Command 056
+echo Command 057
+echo Command 058
+echo Command 059
+echo Command 060
+echo Command 061
+echo Command 062
+echo Command 063
+echo Command 064
+echo Command 065
+echo Command 066
+echo Command 067
+echo Command 068
+echo Command 069
+echo Command 070
+echo Command 071
+echo Command 072
+echo Command 073
+echo Command 074
+echo Command 075
+echo Command 076
+echo Command 077
+echo Command 078
+echo Command 079
+echo Command 080
+echo Command 081
+echo Command 082
+echo Command 083
+echo Command 084
+echo Command 085
+echo Command 086
+echo Command 087
+echo Command 088
+echo Command 089
+echo Command 090
+echo Command 091
+echo Command 092
+echo Command 093
+echo Command 094
+echo Command 095
+echo Command 096
+echo Command 097
+echo Command 098
+echo Command 099
+echo Command 100
+echo Command 101
+echo Command 102
+echo Command 103
+echo Command 104
+echo Command 105
+echo Command 106
+echo Command 107
+echo Command 108
+echo Command 109
+echo Command 110
+echo Command 111
+echo Command 112
+echo Command 113
+echo Command 114
+echo Command 115
+echo Command 116
+echo Command 117
+echo Command 118
+echo Command 119
+echo Command 120
+echo Command 121
+echo Command 122
+echo Command 123
+echo Command 124
+echo Command 125
+echo Command 126
+echo Command 127
+echo Command 128
+echo Command 129
+echo Command 130
+# Potato
+echo Command 131
+echo Command 132
+echo Command 133
+echo Command 134
+echo Command 135
+echo Command 136
+echo Command 137
+echo Command 138
+echo Command 139
+echo Command 140
+echo Command 141
+echo Command 142
+echo Command 143
+echo Command 144
+echo Command 145
+echo Command 146
+echo Command 147
+echo Command 148
+echo Command 149
+echo Command 150
+echo Command 151
+echo Command 152
+echo Command 153
+echo Command 154
+echo Command 155
+echo Command 156
+echo Command 157
+echo Command 158
+echo Command 159
+echo Command 160
+echo Command 161
+echo Command 162
+echo Command 163
+echo Command 164
+echo Command 165
+echo Command 166
+echo Command 167
+echo Command 168
+echo Command 169
+echo Command 170
+echo Command 171
+echo Command 172
+echo Command 173
+echo Command 174
+echo Command 175
+echo Command 176
+echo Command 177
+echo Command 178
+echo Command 179
+echo Command 180
+echo Command 181
+echo Command 182
+echo Command 183
+echo Command 184
+echo Command 185
+echo Command 186
+echo Command 187
+echo Command 188
+echo Command 189
+echo Command 190
+echo Command 191
+echo Command 192
+echo Command 193
+echo Command 194
+echo Command 195
+echo Command 196
+echo Command 197
+echo Command 198
+echo Command 199
+echo Command 200
+echo Command 201
+echo Command 202
+echo Command 203
+echo Command 204
+echo Command 205
+echo Command 206
+echo Command 207
+echo Command 208
+echo Command 209
+echo Command 210
+echo Command 211
+echo Command 212
+echo Command 213
+echo Command 214
+echo Command 215
+echo Command 216
+echo Command 217
+echo Command 218
+echo Command 219
+echo Command 220
+echo Command 221
+echo Command 222
+echo Command 223
+echo Command 224
+echo Command 225
+echo Command 226
+echo Command 227
+echo Command 228
+echo Command 229
+echo Command 230
+echo Command 231
+echo Command 232
+echo Command 233
+echo Command 234
+echo Command 235
+echo Command 236
+echo Command 237
+echo Command 238
+echo Command 239
+echo Command 240
+echo Command 241
+echo Command 242
+echo Command 243
+echo Command 244
+echo Command 245
+echo Command 246
+echo Command 247
+echo Command 248
+echo Command 249
+echo Command 250
+echo Command 251
+echo Command 252
+echo Command 253
+echo Command 254
+echo Command 255
+echo Command 256
+echo Command 257
+echo Command 258
+echo Command 259
+echo Command 260
+echo Command 261
+echo Command 262
+echo Command 263
+echo Command 264
+echo Command 265
+echo Command 266
+echo Command 267
+echo Command 268
+echo Command 269
+echo Command 270
+echo Command 271
+echo Command 272
+echo Command 273
+echo Command 274
+echo Command 275
+echo Command 276
+echo Command 277
+echo Command 278
+echo Command 279
+echo Command 280
+echo Command 281
+echo Command 282
+echo Command 283
+echo Command 284
+echo Command 285
+echo Command 286
+echo Command 287
+echo Command 288
+echo Command 289
+echo Command 290
+echo Command 291
+echo Command 292
+echo Command 293
+echo Command 294
+echo Command 295
+echo Command 296
+echo Command 297
+echo Command 298
+echo Command 299
+echo Command 300
+echo Command 301
+echo Command 302
+echo Command 303
+echo Command 304
+echo Command 305
+echo Command 306
+echo Command 307
+echo Command 308
+echo Command 309
+echo Command 310
+echo Command 311
+echo Command 312
+echo Command 313
+echo Command 314
+echo Command 315
+echo Command 316
+echo Command 317
+echo Command 318
+echo Command 319
+echo Command 320
+echo Command 321
+echo Command 322
+echo Command 323
+echo Command 324
+echo Command 325
+echo Command 326
+echo Command 327
+echo Command 328
+echo Command 329
+echo Command 330
+echo Command 331
+echo Command 332
+echo Command 333
+echo Command 334
+echo Command 335
+echo Command 336
+echo Command 337
+echo Command 338
+echo Command 339
+echo Command 340
+echo Command 341
+echo Command 342
+echo Command 343
+echo Command 344
+echo Command 345
+echo Command 346
+echo Command 347
+echo Command 348
+echo Command 349
+echo Command 350
+echo Command 351
+echo Command 352
+echo Command 353
+echo Command 354
+echo Command 355
+echo Command 356
+echo Command 357
+echo Command 358
+echo Command 359
+echo Command 360
+echo Command 361
+echo Command 362
+echo Command 363
+echo Command 364
+echo Command 365
+echo Command 366
+echo Command 367
+echo Command 368
+echo Command 369
+echo Command 370
+echo Command 371
+ls /
+echo Command 373
+echo Command 374
+echo Command 375
+echo Command 376
+echo Command 377
+echo Command 378
+echo Command 379
+echo Command 380
+echo Command 381
+echo Command 383
+echo Command 384
+mkdir /a
+ls /a
+echo Command 385
+echo Command 386
+echo Command 387
+echo Command 388
+mysterycommand
+echo Command 389
+echo Command 390
+echo Command 391
+echo Command 392
+grep Potato$ /README.md
+grep Potato$ /4.sh
+echo Command 394
+echo Command 395
+echo Command 396
+echo Command 397
+echo Command 398
+echo Command 399
+echo Command 400
+echo Command 401
+echo Command 402
+echo Command 403
+echo Command 404
+echo Command 405
+wc /README.md
+echo Command 407
+echo Command 408
+echo Command 409
+echo Command 410
+echo Command 411
+echo Command 412
+echo Command 413
+echo Command 414
+echo Command 415
+echo Command 416
+echo Command 417
+echo Command 418
+echo Command 419
+echo -----
+!ls      # ls an empty dir
+!m       # run mysterycommand and fail since it doesn't exist
+!grepfzw # no command had this prefix
+!grep    # find 'Potato' in this script (*not* in README.md)
+!w       # word count README.md		
+!gr      # find 'Potato' again
+!e       # last echo command (-----)
diff --git a/Makefile b/Makefile
index 477d25f..9496185 100644
--- a/Makefile
+++ b/Makefile
@@ -83,11 +83,14 @@ endif
 
 LDFLAGS = -z max-page-size=4096
 
-$K/kernel: $(OBJS) $K/kernel.ld
+$K/kernel: $(OBJS) $K/kernel.ld $K/strace.h
 	$(LD) $(LDFLAGS) -T $K/kernel.ld -o $K/kernel $(OBJS) 
 	$(OBJDUMP) -S $K/kernel > $K/kernel.asm
 	$(OBJDUMP) -t $K/kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $K/kernel.sym
 
+$K/strace.h: generate-traces.sh $U/user.h
+		./generate-traces.sh > $K/strace.h
+
 $K/%.o: $K/%.S
 	$(CC) -g -c -o $@ $<
 
@@ -110,7 +113,7 @@ $U/usys.o : $U/usys.S
 $U/_forktest: $U/forktest.o $(ULIB)
 	# forktest has less library code linked in - needs to be small
 	# in order to be able to max out the proc table.
-	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $U/_forktest $U/forktest.o $U/ulib.o $U/usys.o
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $U/_forktest $U/forktest.o $U/ulib.o $U/usys.o $U/umalloc.o $U/printf.o
 	$(OBJDUMP) -S $U/_forktest > $U/forktest.asm
 
 mkfs/mkfs: mkfs/mkfs.c $K/fs.h $K/param.h
@@ -123,20 +126,43 @@ mkfs/mkfs: mkfs/mkfs.c $K/fs.h $K/param.h
 .PRECIOUS: %.o
 
 UPROGS=\
+	$U/_about\
+	$U/_barca\
+	$U/_benchmark\
+	$U/_broken\
 	$U/_cat\
+	$U/_catlines\
 	$U/_compress\
 	$U/_compress_test\
+	$U/_clear\
+	$U/_clock\
 	$U/_echo\
+	$U/_fnr\
 	$U/_forktest\
+	$U/_freemem\
 	$U/_grep\
 	$U/_init\
 	$U/_kill\
+	$U/_leetify\
 	$U/_ln\
 	$U/_ls\
 	$U/_mkdir\
+	$U/_mmap\
+	$U/_mmaptest\
+	$U/_mt70\
+	$U/_mt80\
+	$U/_mt90\
+	$U/_nice\
+	$U/_opt_cat\
+	$U/_pwd\
 	$U/_rm\
+	$U/_reboot\
 	$U/_sh\
+	$U/_shutdown\
+	$U/_spinner\
+	$U/_strace\
 	$U/_stressfs\
+	$U/_tolower\
 	$U/_usertests\
 	$U/_grind\
 	$U/_wc\
@@ -145,8 +171,8 @@ UPROGS=\
 	$U/_forphan\
 	$U/_dorphan\
 
-fs.img: mkfs/mkfs README.md $(UPROGS)
-	mkfs/mkfs fs.img README.md $(UPROGS)
+fs.img: mkfs/mkfs README.md tm.txt input.txt $(UPROGS) script.sh spin1.sh spin2.sh 1.sh 2.sh 
+	mkfs/mkfs fs.img README.md tm.txt input.txt $(UPROGS) script.sh spin1.sh spin2.sh 1.sh 2.sh
 
 -include kernel/*.d user/*.d
 
diff --git a/kernel/exec.c b/kernel/exec.c
index 7cb6fe5..061e574 100644
--- a/kernel/exec.c
+++ b/kernel/exec.c
@@ -44,6 +44,37 @@ kexec(char *path, char **argv)
   }
   ilock(ip);
 
+  // check for shebang (#!)
+  char shebang[2];
+  if(readi(ip, 0, (uint64)shebang, 0, 2) == 2 && shebang[0] == '#' && shebang[1] == '!') {
+  	// now read the interpreter
+  	char interpreter[MAXPATH];
+  	int n = readi(ip, 0, (uint64)interpreter, 2, MAXPATH);
+  	if (n <= 0)
+  		goto bad;
+
+  	// find \n and remove it from the interpreter
+  	for (i = 0; i < n; i++) {
+  		if(interpreter[i] == '\n') {
+  			interpreter[i] = '\0';
+  			break;
+  		}
+  	}
+
+  	// build new argv array to pass to kexec
+  	char *new_argv[MAXARG];
+  	new_argv[0] = interpreter;
+  	new_argv[1] = path;
+  	for (i = 1; argv[1] && i < MAXARG - 2; i++)
+  		new_argv[i + 1] = argv[i];
+  	new_argv[i + 1] = 0;
+
+  	// unlock and end any file system log operations
+  	iunlockput(ip);
+  	end_op();
+  	return kexec(interpreter, new_argv);
+  }
+
   // Read the ELF header.
   if(readi(ip, 0, (uint64)&elf, 0, sizeof(elf)) != sizeof(elf))
     goto bad;
@@ -133,6 +164,10 @@ kexec(char *path, char **argv)
   p->sz = sz;
   p->trapframe->epc = elf.entry;  // initial program counter = main
   p->trapframe->sp = sp; // initial stack pointer
+
+  p->mmap = TRAPFRAME - (USERSTACK * PGSIZE);
+  p->mmap_pages = 0;
+  
   proc_freepagetable(oldpagetable, oldsz);
 
   return argc; // this ends up in a0, the first argument to main(argc, argv)
diff --git a/kernel/fs.c b/kernel/fs.c
index 9274678..19ecc66 100644
--- a/kernel/fs.c
+++ b/kernel/fs.c
@@ -718,3 +718,96 @@ nameiparent(char *path, char *name)
 {
   return namex(path, 1, name);
 }
+
+// Get the name of a particular inode in a directory.
+int
+diriname(struct inode *dp, ushort inum, char name[DIRSIZ], ushort *iparent)
+{
+  ilock(dp);
+
+  if (dp->type != T_DIR)
+    panic("diriname not DIR");
+
+  struct dirent de;
+  if (iparent) {
+    // Read second entry ('..', aka parent)
+    readi(dp, 0, (uint64) &de, sizeof(struct dirent), sizeof(struct dirent));
+    *iparent = de.inum;
+  }
+
+  for (uint off = 0; off < dp->size; off += sizeof(de)){
+    if (readi(dp, 0, (uint64) &de, off, sizeof(de)) != sizeof(de))
+      panic("diriname read");
+    if (de.inum == 0)
+      continue;
+    if (de.inum == inum && name) {
+      // Found the inode
+      strncpy(name, de.name, DIRSIZ);
+      iunlockput(dp);
+      return strlen(name);
+    }
+  }
+
+  iunlockput(dp);
+  return -1;
+}
+
+int
+getcwd(char *buf, uint size)
+{
+  struct inode *ip = myproc()->cwd;
+  ilock(ip);
+
+  if(ip->type != T_DIR)
+    panic("getcwd not DIR");
+
+  if (!buf || size <= 1) {
+    iunlock(ip);
+    return -1;
+  }
+
+  if (ip->inum == 1 && size > 1) {
+    buf[0] = '/';
+    buf[1] = '\0';
+    iunlock(ip);
+    return 0;
+  }
+
+  // We copy the path to the *end* of the buffer instead of the beginning, then
+  // work backwards. Start by null terminating the string.
+  buf[size - 1] = '\0';
+  uint bufp = size - 2;
+
+  struct inode *i = iget(ip->dev, ip->inum);
+
+  ushort iparent;
+  ushort last_parent = ip->inum;
+  ushort icurrent = ip->inum;
+  char name[DIRSIZ];
+  iunlock(ip);
+
+  // Starting with the CWD inode, go up one level (..), read that directory, and
+  // search for the CWD inode in it. Repeat the process until we reach /.
+  while (icurrent != 1 && diriname(i, icurrent, name, &iparent) != -1) {
+    if (icurrent != last_parent) {
+      // We found another path element. Add it to the string.
+      int len = strlen(name);
+      if (len < bufp) {
+        bufp -= len;
+        memmove(buf + bufp, name, len);
+        buf[--bufp] = '/';
+      } else {
+        // No more space to store the path.
+        break;
+      }
+    }
+    i = iget(ip->dev, iparent);
+    icurrent = last_parent;
+    last_parent = iparent;
+  }
+
+  // If we didn't use the entire buffer, slide the string over to the beginning.
+  memmove(buf, buf + bufp, size - bufp);
+
+  return 0;
+}
diff --git a/kernel/memlayout.h b/kernel/memlayout.h
index 9bc9424..3848ff4 100644
--- a/kernel/memlayout.h
+++ b/kernel/memlayout.h
@@ -25,6 +25,12 @@
 #define VIRTIO0 0x10001000
 #define VIRTIO0_IRQ 1
 
+// goldfish_rtc clock
+#define GOLDFISH 0x101000
+
+// qemu "test" device for signaling exit/status
+#define VIRT_TEST 0x100000
+
 // qemu puts platform-level interrupt controller (PLIC) here.
 #define PLIC 0x0c000000L
 #define PLIC_PRIORITY (PLIC + 0x0)
diff --git a/kernel/proc.c b/kernel/proc.c
index 9d6cf3f..f1bf4fa 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -125,6 +125,12 @@ allocproc(void)
   p->pid = allocpid();
   p->state = USED;
 
+  p->nice = 1;
+  p->priority = 3 - p->nice; 
+
+  p->mmap = 0;
+  p->mmap_pages = 0;
+
   // Allocate a trapframe page.
   if((p->trapframe = (struct trapframe *)kalloc()) == 0){
     freeproc(p);
@@ -158,8 +164,15 @@ freeproc(struct proc *p)
   if(p->trapframe)
     kfree((void*)p->trapframe);
   p->trapframe = 0;
-  if(p->pagetable)
-    proc_freepagetable(p->pagetable, p->sz);
+  if (p->pagetable) {
+  	if (p->mmap_pages > 0) {
+  		uvmunmap(p->pagetable, p->mmap, p->mmap_pages, 1);
+  		p->mmap_pages = 0;
+  		p->mmap = 0;
+  	}
+  	proc_freepagetable(p->pagetable, p->sz);
+  }
+    
   p->pagetable = 0;
   p->sz = 0;
   p->pid = 0;
@@ -168,6 +181,7 @@ freeproc(struct proc *p)
   p->chan = 0;
   p->killed = 0;
   p->xstate = 0;
+  p->tracing = 0;
   p->state = UNUSED;
 }
 
@@ -279,6 +293,25 @@ kfork(void)
   // Cause fork to return 0 in the child.
   np->trapframe->a0 = 0;
 
+  np->mmap = p->mmap;
+  np->mmap_pages = p->mmap_pages;
+
+  for (i = 0; i < p->mmap_pages; i++) {
+  	uint64 va = p->mmap + (uint64)i * PGSIZE;
+
+  	uint64 pa = walkaddr(p->pagetable, va);
+  	if (pa == 0)
+  		panic("kfork: mmap walkaddr failed");
+
+
+  	if(mappages(np->pagetable, va, PGSIZE, pa,
+  				PTE_R | PTE_W | PTE_U) < 0)
+  	   panic("kfrok: mmap mappages failed");
+
+
+  	incref(pa);
+  }
+
   // increment reference counts on open file descriptors.
   for(i = 0; i < NOFILE; i++)
     if(p->ofile[i])
@@ -287,6 +320,9 @@ kfork(void)
 
   safestrcpy(np->name, p->name, sizeof(p->name));
 
+  np->nice = p->nice; // copy parent's nicenessœ
+  np->priority = p->priority;
+  
   pid = np->pid;
 
   release(&np->lock);
@@ -411,6 +447,64 @@ kwait(uint64 addr)
   }
 }
 
+// Wait for a child process to exit and return its pid.
+// Return -1 if this process has no children.
+int
+kwait2(uint64 addr, uint64 addr2)
+{
+  struct proc *pp;
+  int havekids, pid;
+  struct proc *p = myproc();
+
+  acquire(&wait_lock);
+
+  for(;;){
+    // Scan through table looking for exited children.
+    havekids = 0;
+    for(pp = proc; pp < &proc[NPROC]; pp++){
+      if(pp->parent == p){
+        // make sure the child isn't still in exit() or swtch().
+        acquire(&pp->lock);
+
+        havekids = 1;
+        if(pp->state == ZOMBIE){
+          // Found one.
+          pid = pp->pid;
+          if(addr != 0 && copyout(p->pagetable, addr, (char *)&pp->xstate,
+                                  sizeof(pp->xstate)) < 0) {
+            release(&pp->lock);
+            release(&wait_lock);
+            return -1;
+          }
+
+		  // copy syscall count to user
+		  if(addr2 != 0 && copyout(p->pagetable, addr2, (char *)&pp->counter,
+		                                    sizeof(pp->counter)) < 0) {
+		              release(&pp->lock);
+		              release(&wait_lock);
+		              return -1;
+		            }
+          
+          freeproc(pp);
+          release(&pp->lock);
+          release(&wait_lock);
+          return pid;
+        }
+        release(&pp->lock);
+      }
+    }
+
+    // No point waiting if we don't have any children.
+    if(!havekids || killed(p)){
+      release(&wait_lock);
+      return -1;
+    }
+    
+    // Wait for a child to exit.
+    sleep(p, &wait_lock);  //DOC: wait-sleep
+  }
+}
+
 // Per-CPU process scheduler.
 // Each CPU calls scheduler() after setting itself up.
 // Scheduler never returns.  It loops, doing:
@@ -426,39 +520,64 @@ scheduler(void)
 
   c->proc = 0;
   for(;;){
-    // The most recent process to run may have had interrupts
-    // turned off; enable them to avoid a deadlock if all
-    // processes are waiting. Then turn them back off
-    // to avoid a possible race between an interrupt
-    // and wfi.
-    intr_on();
-    intr_off();
-
-    int found = 0;
-    for(p = proc; p < &proc[NPROC]; p++) {
-      acquire(&p->lock);
-      if(p->state == RUNNABLE) {
-        // Switch to chosen process.  It is the process's job
-        // to release its lock and then reacquire it
-        // before jumping back to us.
-        p->state = RUNNING;
-        c->proc = p;
-        swtch(&c->context, &p->context);
-
-        // Process is done running for now.
-        // It should have changed its p->state before coming back.
-        c->proc = 0;
-        found = 1;
+  // The most recent process to run may have had interrupts
+  // turned off; enable them to avoid a deadlock if all
+  // processes are waiting. Then turn them back off
+  // to avoid a possible race between an interrupt
+  // and wfi.
+  intr_on();
+  intr_off();
+
+  int found = 0;
+
+  // Find the highest priority among RUNNABLE processes
+  // so we can start scanning from there
+  int max_priority = -1;
+  for(p = proc; p < &proc[NPROC]; p++){
+    acquire(&p->lock);
+    if(p->state == RUNNABLE && p->priority > max_priority)
+      max_priority = p->priority;
+    release(&p->lock);
+  }
+
+  // Iterate priority "levels" from highest we observed down to 0.
+  // At each level, run any RUNNABLE process whose priority is >= level.
+  if(max_priority >= 0){
+    for(int level = max_priority; level >= 0; level--){
+      int found_runnable = 0;
+
+      for(p = proc; p < &proc[NPROC]; p++){
+        acquire(&p->lock);
+        if(p->state == RUNNABLE && p->priority >= level){
+          found_runnable = 1;
+
+          // Switch to chosen process. It is the process's job
+          // to release its lock and then reacquire it
+          // before jumping back to us.
+          p->state = RUNNING;
+          c->proc = p;
+          swtch(&c->context, &p->context);
+
+          // Process is done running for now.
+          // It should have changed its p->state before coming back.
+          c->proc = 0;
+          found = 1;
+        }
+        release(&p->lock);
       }
-      release(&p->lock);
-    }
-    if(found == 0) {
-      // nothing to run; stop running on this core until an interrupt.
-      asm volatile("wfi");
+
+      // If no process qualified at this level, just drop to the next one.
+      if(!found_runnable)
+        continue;
     }
   }
-}
 
+  if(found == 0){
+    // nothing to run; stop running on this core until an interrupt.
+    asm volatile("wfi");
+  }
+ }
+} 
 // Switch to scheduler.  Must hold only p->lock
 // and have changed proc->state. Saves and restores
 // intena because intena is a property of this
@@ -681,7 +800,7 @@ procdump(void)
       state = states[p->state];
     else
       state = "???";
-    printf("%d %s %s", p->pid, state, p->name);
+    printf("%d %s %s priority=%d nice=%d\n", p->pid, state, p->name, p->priority, p->nice);
     printf("\n");
   }
 }
diff --git a/kernel/proc.h b/kernel/proc.h
index d021857..d591306 100644
--- a/kernel/proc.h
+++ b/kernel/proc.h
@@ -91,6 +91,10 @@ struct proc {
   int killed;                  // If non-zero, have been killed
   int xstate;                  // Exit status to be returned to parent's wait
   int pid;                     // Process ID
+  int tracing;                 // Trace Flag
+  int counter;                 // Counter for tracking SYS calls
+  int nice;                    // (0 = highest priority) 
+  int priority;                // (derived: prio = 3 - nice; higher number = higher priority)
 
   // wait_lock must be held when using this:
   struct proc *parent;         // Parent process
@@ -98,6 +102,10 @@ struct proc {
   // these are private to the process, so p->lock need not be held.
   uint64 kstack;               // Virtual address of kernel stack
   uint64 sz;                   // Size of process memory (bytes)
+
+  uint64 mmap;                 // lowest virtual address used by mmap region
+  int mmap_pages;              // number of mmap pages currently mapped
+  
   pagetable_t pagetable;       // User page table
   struct trapframe *trapframe; // data page for trampoline.S
   struct context context;      // swtch() here to run process
diff --git a/kernel/strace.h b/kernel/strace.h
new file mode 100644
index 0000000..3fb96c2
--- /dev/null
+++ b/kernel/strace.h
@@ -0,0 +1,121 @@
+#include "defs.h"
+#include "syscall.h"
+#pragma GCC diagnostic ignored "-Wunused-function"
+
+static uint64
+read_int(int n)
+{
+  int i;
+  argint(n, &i);
+  return i;
+}
+
+static void *
+read_ptr(int n)
+{
+  // TODO: read an argument as a pointer. wait() in sysproc.c
+  // is a good example of doing this.
+  uint64 addr;
+  argaddr(n, &addr);
+  return (void *)addr;
+}
+
+static char *
+read_str(int n)
+{
+  // TODO: read an argument as a string. open() or mkdir() in sysfile.c 
+  // are good examples of doing this.
+  static char buf[128];
+  if (argstr(n, buf, sizeof(buf)) < 0)
+  	return "(null)";
+  return buf;
+}
+
+void
+strace(struct proc *p, int syscall_num, uint64 ret_val)
+{
+  // printf("[strace] syscall: %d\n", syscall_num);
+  // This will drop the raw syscall output here, so it's commented out for
+  // now... we need to update this function so that it prints system call
+  // tracing information (based on the syscall_num passed in).
+  switch(syscall_num){
+	case SYS_fork:
+  printf("[%d|%s] fork() = %ld\n", p->pid, p->name,   ret_val);
+ break;
+case SYS_exit:
+  printf("[%d|%s] exit(int = %ld) = %ld\n", p->pid, p->name, read_int(0),   ret_val);
+ break;
+case SYS_wait:
+  printf("[%d|%s] wait(status = %p) = %ld\n", p->pid, p->name, read_ptr(0),   ret_val);
+ break;
+case SYS_pipe:
+  printf("[%d|%s] pipe(pipefd = %p) = %ld\n", p->pid, p->name, read_ptr(0),   ret_val);
+ break;
+case SYS_read:
+  printf("[%d|%s] read(fd = %ld, buf = %p, count = %ld) = %ld\n", p->pid, p->name, read_int(0), read_ptr(1), read_int(2),   ret_val);
+ break;
+case SYS_write:
+  printf("[%d|%s] write(fd = %ld, buf = %p, count = %ld) = %ld\n", p->pid, p->name, read_int(0), read_ptr(1), read_int(2),   ret_val);
+ break;
+case SYS_close:
+  printf("[%d|%s] close(fd = %ld) = %ld\n", p->pid, p->name, read_int(0),   ret_val);
+ break;
+case SYS_kill:
+  printf("[%d|%s] kill(pid = %ld) = %ld\n", p->pid, p->name, read_int(0),   ret_val);
+ break;
+case SYS_exec:
+  printf("[%d|%s] exec(path = %p, argv = %p) = %ld\n", p->pid, p->name, read_ptr(0), read_ptr(1),   ret_val);
+ break;
+case SYS_open:
+  printf("[%d|%s] open(path = %s, mode = %ld) = %ld\n", p->pid, p->name, read_str(0), read_int(1),   ret_val);
+ break;
+case SYS_mknod:
+  printf("[%d|%s] mknod(path = %s, major = %ld, minor = %ld) = %ld\n", p->pid, p->name, read_str(0), read_int(1), read_int(2),   ret_val);
+ break;
+case SYS_unlink:
+  printf("[%d|%s] unlink(path = %s) = %ld\n", p->pid, p->name, read_str(0),   ret_val);
+ break;
+case SYS_fstat:
+  printf("[%d|%s] fstat(fd = %ld, st = %p) = %ld\n", p->pid, p->name, read_int(0), read_ptr(1),   ret_val);
+ break;
+case SYS_link:
+  printf("[%d|%s] link(old_path = %s, new_path = %s) = %ld\n", p->pid, p->name, read_str(0), read_str(1),   ret_val);
+ break;
+case SYS_mkdir:
+  printf("[%d|%s] mkdir(path = %s) = %ld\n", p->pid, p->name, read_str(0),   ret_val);
+ break;
+case SYS_chdir:
+  printf("[%d|%s] chdir(path = %s) = %ld\n", p->pid, p->name, read_str(0),   ret_val);
+ break;
+case SYS_dup:
+  printf("[%d|%s] dup(fd = %ld) = %ld\n", p->pid, p->name, read_int(0),   ret_val);
+ break;
+case SYS_getpid:
+  printf("[%d|%s] getpid() = %ld\n", p->pid, p->name,   ret_val);
+ break;
+case SYS_sbrk:
+  printf("[%d|%s] sbrk(int = %ld) = %p\n", p->pid, p->name, read_int(0),  (void *) ret_val);
+ break;
+case SYS_pause:
+  printf("[%d|%s] pause(int = %ld) = %ld\n", p->pid, p->name, read_int(0),   ret_val);
+ break;
+case SYS_uptime:
+  printf("[%d|%s] uptime() = %ld\n", p->pid, p->name,   ret_val);
+ break;
+case SYS_shutdown:
+  printf("[%d|%s] shutdown() = %ld\n", p->pid, p->name,   ret_val);
+ break;
+case SYS_reboot:
+  printf("[%d|%s] reboot() = %ld\n", p->pid, p->name,   ret_val);
+ break;
+case SYS_clock:
+  printf("[%d|%s] clock() = %ld\n", p->pid, p->name,   ret_val);
+ break;
+case SYS_strace_on:
+  printf("[%d|%s] strace_on() = %ld\n", p->pid, p->name,   ret_val);
+ break;
+case SYS_wait2:
+  printf("[%d|%s] wait2(status = %p, counter = %p) = %ld\n", p->pid, p->name, read_ptr(0), read_ptr(1),   ret_val);
+ break;
+  }
+}
diff --git a/kernel/syscall.c b/kernel/syscall.c
index 076d965..fc2075c 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -6,6 +6,7 @@
 #include "proc.h"
 #include "syscall.h"
 #include "defs.h"
+#include "strace.h"
 
 // Fetch the uint64 at addr from the current process.
 int
@@ -101,6 +102,15 @@ extern uint64 sys_unlink(void);
 extern uint64 sys_link(void);
 extern uint64 sys_mkdir(void);
 extern uint64 sys_close(void);
+extern uint64 sys_shutdown(void);
+extern uint64 sys_reboot(void);
+extern uint64 sys_clock(void);
+extern uint64 sys_strace_on(void);
+extern uint64 sys_wait2(void);
+extern uint64 sys_nice(void);
+extern uint64 sys_getcwd(void);
+extern uint64 sys_freemem(void);
+extern uint64 sys_mmap(void);
 
 // An array mapping syscall numbers from syscall.h
 // to the function that handles the system call.
@@ -126,6 +136,15 @@ static uint64 (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
+[SYS_shutdown]  sys_shutdown,
+[SYS_reboot] sys_reboot,
+[SYS_clock] sys_clock,
+[SYS_strace_on] sys_strace_on,
+[SYS_wait2] sys_wait2,
+[SYS_nice] sys_nice,
+[SYS_getcwd] sys_getcwd,
+[SYS_freemem] sys_freemem,
+[SYS_mmap] sys_mmap,
 };
 
 void
@@ -138,7 +157,14 @@ syscall(void)
   if(num > 0 && num < NELEM(syscalls) && syscalls[num]) {
     // Use num to lookup the system call function for num, call it,
     // and store its return value in p->trapframe->a0
-    p->trapframe->a0 = syscalls[num]();
+	p->counter++; // increase sys call counter 
+    
+    uint64 ptr = syscalls[num]();
+   
+    if (p->tracing) {
+    	strace(p, num, ptr);
+    }
+    p->trapframe->a0 = ptr;
   } else {
     printf("%d %s: unknown sys call %d\n",
             p->pid, p->name, num);
diff --git a/kernel/syscall.h b/kernel/syscall.h
index 3dd926d..5e11c4c 100644
--- a/kernel/syscall.h
+++ b/kernel/syscall.h
@@ -20,3 +20,12 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
+#define SYS_shutdown 22
+#define SYS_reboot 23
+#define SYS_clock 24
+#define SYS_strace_on 25
+#define SYS_wait2 26
+#define SYS_nice 27
+#define SYS_getcwd 28
+#define SYS_freemem 29
+#define SYS_mmap 30
diff --git a/kernel/sysfile.c b/kernel/sysfile.c
index d8234ce..e6ca5ba 100644
--- a/kernel/sysfile.c
+++ b/kernel/sysfile.c
@@ -406,6 +406,34 @@ sys_mknod(void)
   return 0;
 }
 
+uint64
+sys_getcwd(void)
+{
+  uint64 ubuf;
+  int sz;
+
+  begin_op();
+  argaddr(0, &ubuf);
+  argint(1, &sz);
+
+  if (sz > PGSIZE) {
+    end_op();
+    return -1;
+  }
+
+  char *buf = kalloc();
+  getcwd(buf, sz);
+
+  if (copyout(myproc()->pagetable, ubuf, buf, sz) < 0) {
+    end_op();
+    return -1;
+  }
+
+  kfree(buf);
+  end_op();
+  return 0;
+}
+
 uint64
 sys_chdir(void)
 {
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index 3044d00..58038e7 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -33,7 +33,16 @@ sys_wait(void)
 {
   uint64 p;
   argaddr(0, &p);
-  return kwait(p);
+  return kwait2(p, 0);
+}
+
+uint64
+sys_wait2(void)
+{
+	uint64 p, p2;
+	argaddr(0, &p);
+	argaddr(1, &p2);
+	return kwait2(p, p2);
 }
 
 uint64
@@ -105,3 +114,96 @@ sys_uptime(void)
   release(&tickslock);
   return xticks;
 }
+
+// shutdown
+uint64
+sys_shutdown(void)
+{
+	volatile uint32 *test_dev = (uint32 *) VIRT_TEST;
+	*test_dev = 0x5555;	
+
+	return 0;
+}
+
+// reboot
+uint64
+sys_reboot(void)
+{
+	volatile uint32 *test_dev = (uint32 *) VIRT_TEST;
+	*test_dev = 0x7777;
+
+	return 0;
+}
+
+uint64
+sys_clock(void)
+{
+	volatile uint32 *base = (uint32*)GOLDFISH;
+
+	uint32 first = base[0];   // low 32 bits
+	uint32 second = base[1];  // high 32 
+
+	return ((uint64)second << 32) | first;
+}
+
+uint64
+sys_strace_on(void)
+{
+	struct proc *p = myproc();
+	p->tracing = 1;
+	return 0;
+}
+
+uint64
+sys_nice(void)
+{
+	int n;
+	argint(0, &n);
+	
+	if (n < 0)  n = 0;
+	if (n > 3) n = 3;
+
+	struct proc *p = myproc();
+	acquire(&p->lock);
+	
+	p->nice = n;
+	p->priority = 3 - n;
+	release(&p->lock);
+	
+	return p->priority;
+}
+
+uint64
+sys_freemem(void)
+{
+  uint64 pages = kfreepages();
+  return pages * (PGSIZE / 1024);
+}
+
+uint64
+sys_mmap(void)
+{
+  struct proc *p = myproc();
+
+  void *pa = kalloc();
+  if(pa == 0)
+    return (uint64)-1;
+
+  memset(pa, 0, PGSIZE);
+
+  uint64 va = p->mmap - PGSIZE;
+
+  if(mappages(p->pagetable, va, PGSIZE, (uint64)pa,
+              PTE_R | PTE_W | PTE_U) < 0){
+    kfree(pa);
+    return (uint64)-1;
+  }
+
+  if(walkaddr(p->pagetable, va) != (uint64)pa)
+    panic("sys_mmap: mapping error");
+
+  p->mmap = va;
+  p->mmap_pages++;
+
+  return va;
+}
diff --git a/mkfs/mkfs.c b/mkfs/mkfs.c
index 5e3873e..67eb79d 100644
--- a/mkfs/mkfs.c
+++ b/mkfs/mkfs.c
@@ -4,18 +4,12 @@
 #include <string.h>
 #include <fcntl.h>
 #include <assert.h>
-#include <sys/types.h>
-#include <dirent.h>
-#include <sys/stat.h>
 
-#define dirent xv6_dirent
 #define stat xv6_stat  // avoid clash with host struct stat
 #include "kernel/types.h"
 #include "kernel/fs.h"
 #include "kernel/stat.h"
 #include "kernel/param.h"
-#undef dirent
-#undef stat
 
 #ifndef static_assert
 #define static_assert(a, b) do { switch (0) case 0: case (a): ; } while (0)
@@ -26,9 +20,9 @@
 // Disk layout:
 // [ boot block | sb block | log | inode blocks | free bit map | data blocks ]
 
-int nbitmap = FSSIZE/(BSIZE*8) + 1;
+int nbitmap = FSSIZE/BPB + 1;
 int ninodeblocks = NINODES / IPB + 1;
-int nlog = LOGBLOCKS;
+int nlog = LOGBLOCKS+1;   // Header followed by LOGBLOCKS data blocks.
 int nmeta;    // Number of meta blocks (boot, sb, nlog, inode, bitmap)
 int nblocks;  // Number of data blocks
 
@@ -71,88 +65,12 @@ xint(uint x)
   return y;
 }
 
-void
-add_file(int parent_fd, uint parentino, char *filename)
-{
-  uint inum;
-  int fd;
-  char buf[BSIZE];
-  struct xv6_dirent de;
-
-  if((fd = openat(parent_fd, filename, 0)) < 0)
-    die(filename);
-
-  inum = ialloc(T_FILE);
-
-  bzero(&de, sizeof(de));
-  de.inum = xshort(inum);
-  strncpy(de.name, filename, DIRSIZ);
-  iappend(parentino, &de, sizeof(de));
-
-  ssize_t cc;
-  while((cc = read(fd, buf, sizeof(buf))) > 0)
-    iappend(inum, buf, cc);
-
-  close(fd);
-}
-
-uint
-add_dir(int level, int parent_fd, uint parentino, char *dirname)
-{
-  struct xv6_dirent de;
-  uint dino = ialloc(T_DIR);
-  bzero(&de, sizeof(de));
-  de.inum = xshort(dino);
-  strcpy(de.name, dirname);
-  iappend(parentino, &de, sizeof(de));
-
-  bzero(&de, sizeof(de));
-  de.inum = xshort(dino);
-  strcpy(de.name, ".");
-  iappend(dino, &de, sizeof(de));
-
-  bzero(&de, sizeof(de));
-  de.inum = xshort(parentino);
-  strcpy(de.name, "..");
-  iappend(dino, &de, sizeof(de));
-
-  int dir_fd = -1;
-  if ((dir_fd = openat(parent_fd, dirname, O_RDONLY)) == -1) {
-    perror("open");
-    return dino;
-  }
-
-  DIR *d = fdopendir(dir_fd);
-  if (d == NULL) {
-    perror("fdopendir");
-    return dino;
-  }
-
-  struct dirent *e;
-  while ((e = readdir(d)) != NULL) {
-    if (e->d_name[0] == '.') {
-      continue;
-    }
-
-    if (e->d_type == DT_REG) {
-      printf("%*s+ %s\n", level * 2, "", e->d_name);
-      add_file(dir_fd, dino, e->d_name);
-    } else if (e->d_type == DT_DIR) {
-      printf("%*s+ /%s\n", level * 2, "", e->d_name);
-      add_dir(level + 1, dir_fd, dino, e->d_name);
-    }
-  }
-  close(dir_fd);
-
-  return dino;
-}
-
 int
 main(int argc, char *argv[])
 {
   int i, cc, fd;
   uint rootino, inum, off;
-  struct xv6_dirent de;
+  struct dirent de;
   char buf[BSIZE];
   struct dinode din;
 
@@ -165,9 +83,9 @@ main(int argc, char *argv[])
   }
 
   assert((BSIZE % sizeof(struct dinode)) == 0);
-  assert((BSIZE % sizeof(struct xv6_dirent)) == 0);
+  assert((BSIZE % sizeof(struct dirent)) == 0);
 
-  fsfd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666);
+  fsfd = open(argv[1], O_RDWR|O_CREATE|O_TRUNC, 0666);
   if(fsfd < 0)
     die(argv[1]);
 
@@ -184,7 +102,7 @@ main(int argc, char *argv[])
   sb.inodestart = xint(2+nlog);
   sb.bmapstart = xint(2+nlog+ninodeblocks);
 
-  printf("nmeta %d (boot, super, log blocks %u inode blocks %u, bitmap blocks %u) blocks %d total %d\n",
+  printf("nmeta %d (boot, super, log blocks %u, inode blocks %u, bitmap blocks %u) blocks %d total %d\n",
          nmeta, nlog, ninodeblocks, nbitmap, nblocks, FSSIZE);
 
   freeblock = nmeta;     // the first free block that we can allocate
@@ -210,13 +128,6 @@ main(int argc, char *argv[])
   iappend(rootino, &de, sizeof(de));
 
   for(i = 2; i < argc; i++){
-    struct stat sb;
-    stat(argv[i], &sb);
-    if (S_ISDIR(sb.st_mode)) {
-      add_dir(0, AT_FDCWD, rootino, argv[i]);
-      continue;
-    }
-
     // get rid of "user/"
     char *shortname;
     if(strncmp(argv[i], "user/", 5) == 0)
@@ -236,6 +147,8 @@ main(int argc, char *argv[])
     if(shortname[0] == '_')
       shortname += 1;
 
+    assert(strlen(shortname) <= DIRSIZ);
+    
     inum = ialloc(T_FILE);
 
     bzero(&de, sizeof(de));
@@ -327,7 +240,7 @@ balloc(int used)
   int i;
 
   printf("balloc: first %d blocks have been allocated\n", used);
-  assert(used < BSIZE*8);
+  assert(used < BPB);
   bzero(buf, BSIZE);
   for(i = 0; i < used; i++){
     buf[i/8] = buf[i/8] | (0x1 << (i%8));
diff --git a/user/sh.c b/user/sh.c
index 278fb37..f5454c6 100644
--- a/user/sh.c
+++ b/user/sh.c
@@ -77,6 +77,14 @@ runcmd(struct cmd *cmd)
     if(ecmd->argv[0] == 0)
       exit(1);
     exec(ecmd->argv[0], ecmd->argv);
+
+	if (strchr(ecmd->argv[0], '/') == 0) {
+		char buf[128];
+		buf[0] = '/';
+		strcpy(buf+1, ecmd->argv[0]);
+		exec(buf, ecmd->argv);
+	}
+    
     fprintf(2, "exec %s failed\n", ecmd->argv[0]);
     break;
 
@@ -132,9 +140,12 @@ runcmd(struct cmd *cmd)
 }
 
 int
-getcmd(char *buf, int nbuf)
+getcmd(char *buf, int nbuf, int is_script)
 {
-  write(2, "$ ", 2);
+  if (!is_script) {
+  	write(2, "$ ", 2);
+  }
+  
   memset(buf, 0, nbuf);
   gets(buf, nbuf);
   if(buf[0] == 0) // EOF
@@ -143,10 +154,11 @@ getcmd(char *buf, int nbuf)
 }
 
 int
-main(void)
+main(int argc, char *argv[])
 {
   static char buf[100];
   int fd;
+  int is_script = 0; // flag to check if we are running a script
 
   // Ensure that three file descriptors are open.
   while((fd = open("console", O_RDWR)) >= 0){
@@ -156,12 +168,22 @@ main(void)
     }
   }
 
+  if (argc > 1) {
+  	is_script = 1;
+  	close(0); // we close stdin
+  	if (open(argv[1], O_RDONLY) < 0) {
+  		fprintf(2, "sh: cannot open %s\n", argv[1]);
+  		exit(1);
+  	}
+  }
+
+
   // Read and run input commands.
-  while(getcmd(buf, sizeof(buf)) >= 0){
+  while(getcmd(buf, sizeof(buf), is_script) >= 0){
     char *cmd = buf;
     while (*cmd == ' ' || *cmd == '\t')
-      cmd++;
-    if (*cmd == '\n') // is a blank command
+      cmd++;	
+    if (*cmd == '\n' || *cmd == '#') // is a blank command
       continue;
     if(cmd[0] == 'c' && cmd[1] == 'd' && cmd[2] == ' '){
       // Chdir must be called by the parent, not the child.
diff --git a/user/user.h b/user/user.h
index ac84de9..718b656 100644
--- a/user/user.h
+++ b/user/user.h
@@ -5,25 +5,34 @@ struct stat;
 // system calls
 int fork(void);
 int exit(int) __attribute__((noreturn));
-int wait(int*);
-int pipe(int*);
-int write(int, const void*, int);
-int read(int, void*, int);
-int close(int);
-int kill(int);
-int exec(const char*, char**);
-int open(const char*, int);
-int mknod(const char*, short, short);
-int unlink(const char*);
-int fstat(int fd, struct stat*);
-int link(const char*, const char*);
-int mkdir(const char*);
-int chdir(const char*);
-int dup(int);
+int wait(int *status);
+int pipe(int *pipefd);
+int write(int fd, const void *buf, int count);
+int read(int fd, void *buf, int count);
+int close(int fd);
+int kill(int pid);
+int exec(const char* path, char **argv);
+int open(const char* path, int mode);
+int mknod(const char* path, short major, short minor);
+int unlink(const char* path);
+int fstat(int fd, struct stat* st);
+int link(const char* old_path, const char* new_path);
+int mkdir(const char* path);
+int chdir(const char* path);
+int dup(int fd);
 int getpid(void);
-char* sys_sbrk(int,int);
+char* sys_sbrk(int n, int incr);
 int pause(int);
 int uptime(void);
+int shutdown(void);
+int reboot(void);
+int clock(void);
+int strace_on(void);
+int wait2(int *status, int *counter);
+int nice(int n);
+int getcwd(char *, int);
+int freemem(void);
+void* mmap(void);
 
 // ulib.c
 int stat(const char*, struct stat*);
@@ -39,6 +48,7 @@ int memcmp(const void *, const void *, uint);
 void *memcpy(void *, const void *, uint);
 char* sbrk(int);
 char* sbrklazy(int);
+int getline(char **buf, int sizep, int fd);
 
 // printf.c
 void fprintf(int, const char*, ...) __attribute__ ((format (printf, 2, 3)));
@@ -47,3 +57,8 @@ void printf(const char*, ...) __attribute__ ((format (printf, 1, 2)));
 // umalloc.c
 void* malloc(uint);
 void free(void*);
+void* calloc(uint, uint);
+void* realloc(void*, uint);
+void malloc_name(void *ptr, const char *name);
+void malloc_print(void);
+void malloc_setfsm(int);
diff --git a/user/usys.pl b/user/usys.pl
index c5d4c3a..983c857 100755
--- a/user/usys.pl
+++ b/user/usys.pl
@@ -42,3 +42,12 @@ sub entry {
 entry("sbrk");
 entry("pause");
 entry("uptime");
+entry("shutdown");
+entry("reboot");
+entry("clock");
+entry("strace_on");
+entry("wait2");
+entry("nice");
+entry("getcwd");
+entry("freemem");
+entry("mmap");

From db273526ccd6c51a6142088ecc051208a7b5f11f Mon Sep 17 00:00:00 2001
From: Kailash Turimella <kailash.turimella@gmail.com>
Date: Tue, 30 Dec 2025 08:34:43 +0530
Subject: [PATCH 3/5] .

---
 kernel/kalloc.c | 68 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 62 insertions(+), 6 deletions(-)

diff --git a/kernel/kalloc.c b/kernel/kalloc.c
index 0699e7e..da58887 100644
--- a/kernel/kalloc.c
+++ b/kernel/kalloc.c
@@ -9,6 +9,16 @@
 #include "riscv.h"
 #include "defs.h"
 
+// Store a reference count for each physical page
+static int ref_count[(PHYSTOP - KERNBASE) / PGSIZE];
+
+// Convert physical address to index in reference count array
+static inline int
+pa2idx(uint64 pa)
+{
+	return (pa - KERNBASE) / PGSIZE;
+}
+
 void freerange(void *pa_start, void *pa_end);
 
 extern char end[]; // first address after kernel.
@@ -23,6 +33,15 @@ struct {
   struct run *freelist;
 } kmem;
 
+void
+incref(uint64 pa)
+{
+	int idx = pa2idx(pa);
+	acquire(&kmem.lock);
+	ref_count[idx]++;
+	release(&kmem.lock);
+}
+
 void
 kinit()
 {
@@ -34,7 +53,7 @@ void
 freerange(void *pa_start, void *pa_end)
 {
   char *p;
-  p = (char*)PGROUNDUP((uint64)pa_start);
+  p = (char*)PGROUNDUP((uint64)pa_start);	
   for(; p + PGSIZE <= (char*)pa_end; p += PGSIZE)
     kfree(p);
 }
@@ -47,18 +66,35 @@ void
 kfree(void *pa)
 {
   struct run *r;
+  uint64 addr = (uint64)pa;
 
-  if(((uint64)pa % PGSIZE) != 0 || (char*)pa < end || (uint64)pa >= PHYSTOP)
+  if((addr % PGSIZE) != 0 || addr < (uint64)end || addr >= PHYSTOP)
     panic("kfree");
 
+  int idx = pa2idx(addr);
+
+  acquire(&kmem.lock);
+
+  if(ref_count[idx] < 0)
+    panic("kfree: ref_count underflow");
+
+  if(ref_count[idx] > 0){
+    // normal case: page was allocated by kalloc
+    ref_count[idx]--;
+    if(ref_count[idx] > 0){
+      // still in use somewhere else – don't free yet
+      release(&kmem.lock);
+      return;
+    }
+  }
+
   // Fill with junk to catch dangling refs.
   memset(pa, 1, PGSIZE);
 
   r = (struct run*)pa;
-
-  acquire(&kmem.lock);
   r->next = kmem.freelist;
   kmem.freelist = r;
+
   release(&kmem.lock);
 }
 
@@ -72,11 +108,31 @@ kalloc(void)
 
   acquire(&kmem.lock);
   r = kmem.freelist;
-  if(r)
+  if(r){
     kmem.freelist = r->next;
+    ref_count[pa2idx((uint64)r)] = 1;   // << MUST be inside lock
+  }
   release(&kmem.lock);
 
   if(r)
-    memset((char*)r, 5, PGSIZE); // fill with junk
+    memset((char*)r, 5, PGSIZE);
+
   return (void*)r;
+}	
+
+uint64
+kfreepages(void)
+{
+	uint64 num_pages = 0;
+	struct run *r;
+
+	acquire(&kmem.lock);
+	r = kmem.freelist;
+	while (r) {
+		num_pages++;
+		r = r->next;
+	}
+	release(&kmem.lock);
+
+	return num_pages;
 }

From 20c1fdc0dced0d328e2fcc95fc228c72cbb6b351 Mon Sep 17 00:00:00 2001
From: Kailash Turimella <kailash.turimella@gmail.com>
Date: Tue, 30 Dec 2025 08:39:32 +0530
Subject: [PATCH 4/5] .

---
 kernel/defs.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/defs.h b/kernel/defs.h
index fdec535..81d57ba 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -53,12 +53,15 @@ int             readi(struct inode*, int, uint64, uint, uint);
 void            stati(struct inode*, struct stat*);
 int             writei(struct inode*, int, uint64, uint, uint);
 void            itrunc(struct inode*);
+int				getcwd(char *, uint);
 void            ireclaim(int);
 
 // kalloc.c
 void*           kalloc(void);
 void            kfree(void *);
 void            kinit(void);
+uint64          kfreepages(void);
+void            incref(uint64 pa);
 
 // log.c
 void            initlog(int, struct superblock*);
@@ -97,6 +100,7 @@ void            sched(void);
 void            sleep(void*, struct spinlock*);
 void            userinit(void);
 int             kwait(uint64);
+int				kwait2(uint64, uint64);
 void            wakeup(void*);
 void            yield(void);
 int             either_copyout(int user_dst, uint64 dst, void *src, uint64 len);

From c0059dc8d7b4b5b7094af72c6dae08087cdb0728 Mon Sep 17 00:00:00 2001
From: Kailash Turimella <kturimella@gojira.cs.usfca.edu>
Date: Wed, 31 Dec 2025 05:47:42 -0800
Subject: [PATCH 5/5] completed

---
 Makefile           |   6 +-
 generate-traces.sh | 147 +++++++++++++
 kernel/param.h     |   2 +-
 mkfs/mkfs.c        |   2 +-
 test.sh            |   9 +
 tm.txt             | 500 +++++++++++++++++++++++++++++++++++++++++++++
 user/about.c       |  13 ++
 user/benchmark.c   |  40 ++++
 user/broken.c      | 324 +++++++++++++++++++++++++++++
 user/catlines.c    |  40 ++++
 user/clear.c       |   8 +
 user/clock.c       |  13 ++
 user/fnr.c         |  29 +++
 user/freemem.c     |  11 +
 user/leetify.c     | 154 ++++++++++++++
 user/mmap.c        |  17 ++
 user/mmaptest.c    |  53 +++++
 user/mt70.c        |  49 +++++
 user/mt80.c        |  49 +++++
 user/mt90.c        |  90 ++++++++
 user/nice.c        |  32 +++
 user/opt_cat.c     |  59 ++++++
 user/pwd.c         |  11 +
 user/reboot.c      |  14 ++
 user/shell.c       | 389 +++++++++++++++++++++++++++++++++++
 user/shutdown.c    |  14 ++
 user/spinner.c     |  28 +++
 user/strace.c      |  21 ++
 user/tolower.c     |  12 ++
 user/ulib.c        |  66 ++++++
 user/umalloc.c     | 485 ++++++++++++++++++++++++++++++++++++-------
 user/user.h        |  12 +-
 user/usys.pl       |   0
 33 files changed, 2613 insertions(+), 86 deletions(-)
 create mode 100755 generate-traces.sh
 create mode 100644 test.sh
 create mode 100644 tm.txt
 create mode 100644 user/about.c
 create mode 100644 user/benchmark.c
 create mode 100644 user/broken.c
 create mode 100644 user/catlines.c
 create mode 100644 user/clear.c
 create mode 100644 user/clock.c
 create mode 100644 user/fnr.c
 create mode 100644 user/freemem.c
 create mode 100644 user/leetify.c
 create mode 100644 user/mmap.c
 create mode 100644 user/mmaptest.c
 create mode 100644 user/mt70.c
 create mode 100644 user/mt80.c
 create mode 100644 user/mt90.c
 create mode 100644 user/nice.c
 create mode 100644 user/opt_cat.c
 create mode 100644 user/pwd.c
 create mode 100644 user/reboot.c
 create mode 100644 user/shell.c
 create mode 100644 user/shutdown.c
 create mode 100644 user/spinner.c
 create mode 100644 user/strace.c
 create mode 100644 user/tolower.c
 mode change 100755 => 100644 user/usys.pl

diff --git a/Makefile b/Makefile
index 9496185..430d995 100644
--- a/Makefile
+++ b/Makefile
@@ -127,7 +127,6 @@ mkfs/mkfs: mkfs/mkfs.c $K/fs.h $K/param.h
 
 UPROGS=\
 	$U/_about\
-	$U/_barca\
 	$U/_benchmark\
 	$U/_broken\
 	$U/_cat\
@@ -158,6 +157,7 @@ UPROGS=\
 	$U/_rm\
 	$U/_reboot\
 	$U/_sh\
+	$U/_shell\
 	$U/_shutdown\
 	$U/_spinner\
 	$U/_strace\
@@ -171,8 +171,8 @@ UPROGS=\
 	$U/_forphan\
 	$U/_dorphan\
 
-fs.img: mkfs/mkfs README.md tm.txt input.txt $(UPROGS) script.sh spin1.sh spin2.sh 1.sh 2.sh 
-	mkfs/mkfs fs.img README.md tm.txt input.txt $(UPROGS) script.sh spin1.sh spin2.sh 1.sh 2.sh
+fs.img: mkfs/mkfs README.md tm.txt $(UPROGS) 1.sh 2.sh 3.sh 4.sh test.sh
+	mkfs/mkfs fs.img README.md tm.txt $(UPROGS) 1.sh 2.sh 3.sh 4.sh test.sh
 
 -include kernel/*.d user/*.d
 
diff --git a/generate-traces.sh b/generate-traces.sh
new file mode 100755
index 0000000..2207f29
--- /dev/null
+++ b/generate-traces.sh
@@ -0,0 +1,147 @@
+#!/usr/bin/env bash
+# This script is designed to be run on a Linux host (i.e., not in xv6)
+# You should probably run this script to see what it does first. To do that, you
+# may need to make it executable:
+#
+# chmod +x generate-traces.sh
+#
+# And then run it from the *root* of your OS directory.
+#
+#
+# For each user space system call stub, this script will print out information
+# about its name, arguments, and return values.
+#
+# You can add information to the stubs that this script will extract. For
+# example, instead of:
+#
+# int write(int, const void *, int);
+#
+# You can add argument names:
+#
+# int write(int fd, const void *buf, int count);
+#
+# And this script will extract them. By default, pointers are assumed to be
+# addresses, but if you want the script to treat them like strings you can add a
+# bit of metadata with a C comment:
+#
+# int mkdir(const char* /*str*/ path);
+#
+# Here's a few examples from a user/user.h file:
+# int exit(int status) __attribute__((noreturn));
+# int wait(int *status);
+# int pipe(int *pipefd);
+# int mkdir(const char* /*str*/ path);
+
+
+# The following code extracts function information from user/user.h based on the
+# system calls found in user/usys.pl.
+
+# Retrieves the type of the argument provided as a printf format specifier
+get_type() {
+    case "${1}" in
+    *'/*str*/'*) echo "%s" ;;
+    *"*"*) echo "%p" ;;
+    *) echo "%ld" ;; # default to int
+    esac
+}
+
+# Determines which function to call for a given format specifier.
+get_conversion() {
+    case "${1}" in
+        '%p') echo "read_ptr(${2})" ;;
+        '%s') echo "read_str(${2})" ;;
+        '%ld') echo "read_int(${2})" ;;
+    esac
+}
+
+# Inspects the user/user.h file to extract system call information
+syscall_output=$(
+for i in $(sed -n 's/entry("\(.*\)");/\1/p' user/usys.pl); do
+    return_value=$(sed -nE \
+        "s:\s*([A-Za-z_][A-Za-z0-9_\* ]+)\s+${i}.*:\1:p;"  user/user.h)
+    args=$(sed 's/const//g; s/void//g; s/struct//g; s/((noreturn))//g' user/user.h \
+        | sed -nE "s:.*\s${i}\((.*)\).*:\1:p")
+
+    # Extract argument names and types for printing
+    arg_list=""
+    arg_convs=""
+    arg_count=0
+    export IFS=","
+    for arg in $args; do
+        arg_name=$(echo "${arg}" | sed -nE 's:.*\b([A-Za-z0-9_]+)\s*:\1:p')
+        arg_type=$(get_type "${arg}")
+        arg_conv=$(get_conversion "${arg_type}" "${arg_count}")
+        arg_list="${arg_list}${arg_name} = ${arg_type}, "
+        arg_convs="${arg_convs}${arg_conv}, "
+        (( arg_count++ ))
+    done
+
+    # Remove extra ', '
+    [[ "${arg_count}" -gt 0 ]] && arg_list="${arg_list::-2}"
+
+    # cast the return type, if necessary
+    return_type="$(get_type "${return_value}")"
+    cast_ret=""
+    if [[ "${return_type}" == "%p" ]]; then
+        cast_ret="(void *)"
+    fi
+
+    # Print out the C code to display system call information. You will probably
+    # need to modify this so it can be used to conditionally print out the
+    # appropriate info.
+    echo "case SYS_${i}:"
+    echo "  printf(\"[%d|%s] ${i}(${arg_list}) = $(get_type "${return_value}")\\n\", p->pid, p->name, ${arg_convs} ${cast_ret} ret_val);"
+    echo " break;"
+done
+)
+
+# The information we want has been extracted and stored in $syscall_output.
+# Using this information, we'll generate C code below. When we run 'cat <<EOM'
+# it tells cat to output everything that follows until the next 'EOM' is found.
+
+cat <<EOM
+#include "defs.h"
+#include "syscall.h"
+#pragma GCC diagnostic ignored "-Wunused-function"
+
+static uint64
+read_int(int n)
+{
+  int i;
+  argint(n, &i);
+  return i;
+}
+
+static void *
+read_ptr(int n)
+{
+  // TODO: read an argument as a pointer. wait() in sysproc.c
+  // is a good example of doing this.
+  uint64 addr;
+  argaddr(n, &addr);
+  return (void *)addr;
+}
+
+static char *
+read_str(int n)
+{
+  // TODO: read an argument as a string. open() or mkdir() in sysfile.c 
+  // are good examples of doing this.
+  static char buf[128];
+  if (argstr(n, buf, sizeof(buf)) < 0)
+  	return "(null)";
+  return buf;
+}
+
+void
+strace(struct proc *p, int syscall_num, uint64 ret_val)
+{
+  // printf("[strace] syscall: %d\n", syscall_num);
+  // This will drop the raw syscall output here, so it's commented out for
+  // now... we need to update this function so that it prints system call
+  // tracing information (based on the syscall_num passed in).
+  switch(syscall_num){
+	${syscall_output}
+  }
+}
+EOM
diff --git a/kernel/param.h b/kernel/param.h
index cd2a41c..abd95e5 100644
--- a/kernel/param.h
+++ b/kernel/param.h
@@ -9,7 +9,7 @@
 #define MAXOPBLOCKS  10  // max # of blocks any FS op writes
 #define LOGBLOCKS    (MAXOPBLOCKS*3)  // max data blocks in on-disk log
 #define NBUF         (MAXOPBLOCKS*3)  // size of disk block cache
-#define FSSIZE       2000  // size of file system in blocks
+#define FSSIZE       4000  // size of file system in blocks
 #define MAXPATH      128   // maximum file path name
 #define USERSTACK    1     // user stack pages
 
diff --git a/mkfs/mkfs.c b/mkfs/mkfs.c
index 67eb79d..5f080bc 100644
--- a/mkfs/mkfs.c
+++ b/mkfs/mkfs.c
@@ -85,7 +85,7 @@ main(int argc, char *argv[])
   assert((BSIZE % sizeof(struct dinode)) == 0);
   assert((BSIZE % sizeof(struct dirent)) == 0);
 
-  fsfd = open(argv[1], O_RDWR|O_CREATE|O_TRUNC, 0666);
+  fsfd = open(argv[1], O_RDWR|O_CREAT|O_TRUNC, 0666);
   if(fsfd < 0)
     die(argv[1]);
 
diff --git a/test.sh b/test.sh
new file mode 100644
index 0000000..9c91a0d
--- /dev/null
+++ b/test.sh
@@ -0,0 +1,9 @@
+#!/crash
+ls /
+echo hi
+mkdir d
+cd d
+ls
+/ls
+/echo bye
+exit
diff --git a/tm.txt b/tm.txt
new file mode 100644
index 0000000..2d3f69a
--- /dev/null
+++ b/tm.txt
@@ -0,0 +1,500 @@
+
+The Time Machine
+An Invention
+
+by H. G. Wells
+
+
+
+
+CONTENTS
+
+ I Introduction
+ II The Machine
+ III The Time Traveller Returns
+ IV Time Travelling
+ V In the Golden Age
+ VI The Sunset of Mankind
+ VII A Sudden Shock
+ VIII Explanation
+ IX The Morlocks
+ X When Night Came
+ XI The Palace of Green Porcelain
+ XII In the Darkness
+ XIII The Trap of the White Sphinx
+ XIV The Further Vision
+ XV The Time Traveller’s Return
+ XVI After the Story
+ Epilogue
+
+
+
+
+ I.
+ Introduction
+
+
+The Time Traveller (for so it will be convenient to speak of him) was
+expounding a recondite matter to us. His pale grey eyes shone and
+twinkled, and his usually pale face was flushed and animated. The fire
+burnt brightly, and the soft radiance of the incandescent lights in the
+lilies of silver caught the bubbles that flashed and passed in our
+glasses. Our chairs, being his patents, embraced and caressed us rather
+than submitted to be sat upon, and there was that luxurious
+after-dinner atmosphere, when thought runs gracefully free of the
+trammels of precision. And he put it to us in this way—marking the
+points with a lean forefinger—as we sat and lazily admired his
+earnestness over this new paradox (as we thought it) and his fecundity.
+
+“You must follow me carefully. I shall have to controvert one or two
+ideas that are almost universally accepted. The geometry, for instance,
+they taught you at school is founded on a misconception.”
+
+“Is not that rather a large thing to expect us to begin upon?” said
+Filby, an argumentative person with red hair.
+
+“I do not mean to ask you to accept anything without reasonable ground
+for it. You will soon admit as much as I need from you. You know of
+course that a mathematical line, a line of thickness _nil_, has no real
+existence. They taught you that? Neither has a mathematical plane.
+These things are mere abstractions.”
+
+“That is all right,” said the Psychologist.
+
+“Nor, having only length, breadth, and thickness, can a cube have a
+real existence.”
+
+“There I object,” said Filby. “Of course a solid body may exist. All
+real things—”
+
+“So most people think. But wait a moment. Can an _instantaneous_ cube
+exist?”
+
+“Don’t follow you,” said Filby.
+
+“Can a cube that does not last for any time at all, have a real
+existence?”
+
+Filby became pensive. “Clearly,” the Time Traveller proceeded, “any
+real body must have extension in _four_ directions: it must have
+Length, Breadth, Thickness, and—Duration. But through a natural
+infirmity of the flesh, which I will explain to you in a moment, we
+incline to overlook this fact. There are really four dimensions, three
+which we call the three planes of Space, and a fourth, Time. There is,
+however, a tendency to draw an unreal distinction between the former
+three dimensions and the latter, because it happens that our
+consciousness moves intermittently in one direction along the latter
+from the beginning to the end of our lives.”
+
+“That,” said a very young man, making spasmodic efforts to relight his
+cigar over the lamp; “that . . . very clear indeed.”
+
+“Now, it is very remarkable that this is so extensively overlooked,”
+continued the Time Traveller, with a slight accession of cheerfulness.
+“Really this is what is meant by the Fourth Dimension, though some
+people who talk about the Fourth Dimension do not know they mean it. It
+is only another way of looking at Time. _There is no difference between
+Time and any of the three dimensions of Space except that our
+consciousness moves along it_. But some foolish people have got hold of
+the wrong side of that idea. You have all heard what they have to say
+about this Fourth Dimension?”
+
+“_I_ have not,” said the Provincial Mayor.
+
+“It is simply this. That Space, as our mathematicians have it, is
+spoken of as having three dimensions, which one may call Length,
+Breadth, and Thickness, and is always definable by reference to three
+planes, each at right angles to the others. But some philosophical
+people have been asking why _three_ dimensions particularly—why not
+another direction at right angles to the other three?—and have even
+tried to construct a Four-Dimensional geometry. Professor Simon Newcomb
+was expounding this to the New York Mathematical Society only a month
+or so ago. You know how on a flat surface, which has only two
+dimensions, we can represent a figure of a three-dimensional solid, and
+similarly they think that by models of three dimensions they could
+represent one of four—if they could master the perspective of the
+thing. See?”
+
+“I think so,” murmured the Provincial Mayor; and, knitting his brows,
+he lapsed into an introspective state, his lips moving as one who
+repeats mystic words. “Yes, I think I see it now,” he said after some
+time, brightening in a quite transitory manner.
+
+“Well, I do not mind telling you I have been at work upon this geometry
+of Four Dimensions for some time. Some of my results are curious. For
+instance, here is a portrait of a man at eight years old, another at
+fifteen, another at seventeen, another at twenty-three, and so on. All
+these are evidently sections, as it were, Three-Dimensional
+representations of his Four-Dimensioned being, which is a fixed and
+unalterable thing.
+
+“Scientific people,” proceeded the Time Traveller, after the pause
+required for the proper assimilation of this, “know very well that Time
+is only a kind of Space. Here is a popular scientific diagram, a
+weather record. This line I trace with my finger shows the movement of
+the barometer. Yesterday it was so high, yesterday night it fell, then
+this morning it rose again, and so gently upward to here. Surely the
+mercury did not trace this line in any of the dimensions of Space
+generally recognised? But certainly it traced such a line, and that
+line, therefore, we must conclude, was along the Time-Dimension.”
+
+“But,” said the Medical Man, staring hard at a coal in the fire, “if
+Time is really only a fourth dimension of Space, why is it, and why has
+it always been, regarded as something different? And why cannot we move
+in Time as we move about in the other dimensions of Space?”
+
+The Time Traveller smiled. “Are you so sure we can move freely in
+Space? Right and left we can go, backward and forward freely enough,
+and men always have done so. I admit we move freely in two dimensions.
+But how about up and down? Gravitation limits us there.”
+
+“Not exactly,” said the Medical Man. “There are balloons.”
+
+“But before the balloons, save for spasmodic jumping and the
+inequalities of the surface, man had no freedom of vertical movement.”
+
+“Still they could move a little up and down,” said the Medical Man.
+
+“Easier, far easier down than up.”
+
+“And you cannot move at all in Time, you cannot get away from the
+present moment.”
+
+“My dear sir, that is just where you are wrong. That is just where the
+whole world has gone wrong. We are always getting away from the present
+moment. Our mental existences, which are immaterial and have no
+dimensions, are passing along the Time-Dimension with a uniform
+velocity from the cradle to the grave. Just as we should travel _down_
+if we began our existence fifty miles above the earth’s surface.”
+
+“But the great difficulty is this,” interrupted the Psychologist. ’You
+_can_ move about in all directions of Space, but you cannot move about
+in Time.”
+
+“That is the germ of my great discovery. But you are wrong to say that
+we cannot move about in Time. For instance, if I am recalling an
+incident very vividly I go back to the instant of its occurrence: I
+become absent-minded, as you say. I jump back for a moment. Of course
+we have no means of staying back for any length of Time, any more than
+a savage or an animal has of staying six feet above the ground. But a
+civilised man is better off than the savage in this respect. He can go
+up against gravitation in a balloon, and why should he not hope that
+ultimately he may be able to stop or accelerate his drift along the
+Time-Dimension, or even turn about and travel the other way?”
+
+“Oh, _this_,” began Filby, “is all—”
+
+“Why not?” said the Time Traveller.
+
+“It’s against reason,” said Filby.
+
+“What reason?” said the Time Traveller.
+
+“You can show black is white by argument,” said Filby, “but you will
+never convince me.”
+
+“Possibly not,” said the Time Traveller. “But now you begin to see the
+object of my investigations into the geometry of Four Dimensions. Long
+ago I had a vague inkling of a machine—”
+
+“To travel through Time!” exclaimed the Very Young Man.
+
+“That shall travel indifferently in any direction of Space and Time, as
+the driver determines.”
+
+Filby contented himself with laughter.
+
+“But I have experimental verification,” said the Time Traveller.
+
+“It would be remarkably convenient for the historian,” the Psychologist
+suggested. “One might travel back and verify the accepted account of
+the Battle of Hastings, for instance!”
+
+“Don’t you think you would attract attention?” said the Medical Man.
+“Our ancestors had no great tolerance for anachronisms.”
+
+“One might get one’s Greek from the very lips of Homer and Plato,” the
+Very Young Man thought.
+
+“In which case they would certainly plough you for the Little-go. The
+German scholars have improved Greek so much.”
+
+“Then there is the future,” said the Very Young Man. “Just think! One
+might invest all one’s money, leave it to accumulate at interest, and
+hurry on ahead!”
+
+“To discover a society,” said I, “erected on a strictly communistic
+basis.”
+
+“Of all the wild extravagant theories!” began the Psychologist.
+
+“Yes, so it seemed to me, and so I never talked of it until—”
+
+“Experimental verification!” cried I. “You are going to verify _that_?”
+
+“The experiment!” cried Filby, who was getting brain-weary.
+
+“Let’s see your experiment anyhow,” said the Psychologist, “though it’s
+all humbug, you know.”
+
+The Time Traveller smiled round at us. Then, still smiling faintly, and
+with his hands deep in his trousers pockets, he walked slowly out of
+the room, and we heard his slippers shuffling down the long passage to
+his laboratory.
+
+The Psychologist looked at us. “I wonder what he’s got?”
+
+“Some sleight-of-hand trick or other,” said the Medical Man, and Filby
+tried to tell us about a conjuror he had seen at Burslem, but before he
+had finished his preface the Time Traveller came back, and Filby’s
+anecdote collapsed.
+
+
+
+
+ II.
+ The Machine
+
+
+The thing the Time Traveller held in his hand was a glittering metallic
+framework, scarcely larger than a small clock, and very delicately
+made. There was ivory in it, and some transparent crystalline
+substance. And now I must be explicit, for this that follows—unless his
+explanation is to be accepted—is an absolutely unaccountable thing. He
+took one of the small octagonal tables that were scattered about the
+room, and set it in front of the fire, with two legs on the hearthrug.
+On this table he placed the mechanism. Then he drew up a chair, and sat
+down. The only other object on the table was a small shaded lamp, the
+bright light of which fell upon the model. There were also perhaps a
+dozen candles about, two in brass candlesticks upon the mantel and
+several in sconces, so that the room was brilliantly illuminated. I sat
+in a low arm-chair nearest the fire, and I drew this forward so as to
+be almost between the Time Traveller and the fireplace. Filby sat
+behind him, looking over his shoulder. The Medical Man and the
+Provincial Mayor watched him in profile from the right, the
+Psychologist from the left. The Very Young Man stood behind the
+Psychologist. We were all on the alert. It appears incredible to me
+that any kind of trick, however subtly conceived and however adroitly
+done, could have been played upon us under these conditions.
+
+The Time Traveller looked at us, and then at the mechanism. “Well?”
+said the Psychologist.
+
+“This little affair,” said the Time Traveller, resting his elbows upon
+the table and pressing his hands together above the apparatus, “is only
+a model. It is my plan for a machine to travel through time. You will
+notice that it looks singularly askew, and that there is an odd
+twinkling appearance about this bar, as though it was in some way
+unreal.” He pointed to the part with his finger. “Also, here is one
+little white lever, and here is another.”
+
+The Medical Man got up out of his chair and peered into the thing.
+“It’s beautifully made,” he said.
+
+“It took two years to make,” retorted the Time Traveller. Then, when we
+had all imitated the action of the Medical Man, he said: “Now I want
+you clearly to understand that this lever, being pressed over, sends
+the machine gliding into the future, and this other reverses the
+motion. This saddle represents the seat of a time traveller. Presently
+I am going to press the lever, and off the machine will go. It will
+vanish, pass into future Time, and disappear. Have a good look at the
+thing. Look at the table too, and satisfy yourselves there is no
+trickery. I don’t want to waste this model, and then be told I’m a
+quack.”
+
+There was a minute’s pause perhaps. The Psychologist seemed about to
+speak to me, but changed his mind. Then the Time Traveller put forth
+his finger towards the lever. “No,” he said suddenly. “Lend me your
+hand.” And turning to the Psychologist, he took that individual’s hand
+in his own and told him to put out his forefinger. So that it was the
+Psychologist himself who sent forth the model Time Machine on its
+interminable voyage. We all saw the lever turn. I am absolutely certain
+there was no trickery. There was a breath of wind, and the lamp flame
+jumped. One of the candles on the mantel was blown out, and the little
+machine suddenly swung round, became indistinct, was seen as a ghost
+for a second perhaps, as an eddy of faintly glittering brass and ivory;
+and it was gone—vanished! Save for the lamp the table was bare.
+
+Everyone was silent for a minute. Then Filby said he was damned.
+
+The Psychologist recovered from his stupor, and suddenly looked under
+the table. At that the Time Traveller laughed cheerfully. “Well?” he
+said, with a reminiscence of the Psychologist. Then, getting up, he
+went to the tobacco jar on the mantel, and with his back to us began to
+fill his pipe.
+
+We stared at each other. “Look here,” said the Medical Man, “are you in
+earnest about this? Do you seriously believe that that machine has
+travelled into time?”
+
+“Certainly,” said the Time Traveller, stooping to light a spill at the
+fire. Then he turned, lighting his pipe, to look at the Psychologist’s
+face. (The Psychologist, to show that he was not unhinged, helped
+himself to a cigar and tried to light it uncut.) “What is more, I have
+a big machine nearly finished in there”—he indicated the
+laboratory—“and when that is put together I mean to have a journey on
+my own account.”
+
+“You mean to say that that machine has travelled into the future?” said
+Filby.
+
+“Into the future or the past—I don’t, for certain, know which.”
+
+After an interval the Psychologist had an inspiration. “It must have
+gone into the past if it has gone anywhere,” he said.
+
+“Why?” said the Time Traveller.
+
+“Because I presume that it has not moved in space, and if it travelled
+into the future it would still be here all this time, since it must
+have travelled through this time.”
+
+“But,” said I, “If it travelled into the past it would have been
+visible when we came first into this room; and last Thursday when we
+were here; and the Thursday before that; and so forth!”
+
+“Serious objections,” remarked the Provincial Mayor, with an air of
+impartiality, turning towards the Time Traveller.
+
+“Not a bit,” said the Time Traveller, and, to the Psychologist: “You
+think. _You_ can explain that. It’s presentation below the threshold,
+you know, diluted presentation.”
+
+“Of course,” said the Psychologist, and reassured us. “That’s a simple
+point of psychology. I should have thought of it. It’s plain enough,
+and helps the paradox delightfully. We cannot see it, nor can we
+appreciate this machine, any more than we can the spoke of a wheel
+spinning, or a bullet flying through the air. If it is travelling
+through time fifty times or a hundred times faster than we are, if it
+gets through a minute while we get through a second, the impression it
+creates will of course be only one-fiftieth or one-hundredth of what it
+would make if it were not travelling in time. That’s plain enough.” He
+passed his hand through the space in which the machine had been. “You
+see?” he said, laughing.
+
+We sat and stared at the vacant table for a minute or so. Then the Time
+Traveller asked us what we thought of it all.
+
+“It sounds plausible enough tonight,” said the Medical Man; “but wait
+until tomorrow. Wait for the common sense of the morning.”
+
+“Would you like to see the Time Machine itself?” asked the Time
+Traveller. And therewith, taking the lamp in his hand, he led the way
+down the long, draughty corridor to his laboratory. I remember vividly
+the flickering light, his queer, broad head in silhouette, the dance of
+the shadows, how we all followed him, puzzled but incredulous, and how
+there in the laboratory we beheld a larger edition of the little
+mechanism which we had seen vanish from before our eyes. Parts were of
+nickel, parts of ivory, parts had certainly been filed or sawn out of
+rock crystal. The thing was generally complete, but the twisted
+crystalline bars lay unfinished upon the bench beside some sheets of
+drawings, and I took one up for a better look at it. Quartz it seemed
+to be.
+
+“Look here,” said the Medical Man, “are you perfectly serious? Or is
+this a trick—like that ghost you showed us last Christmas?”
+
+“Upon that machine,” said the Time Traveller, holding the lamp aloft,
+“I intend to explore time. Is that plain? I was never more serious in
+my life.”
+
+None of us quite knew how to take it.
+
+I caught Filby’s eye over the shoulder of the Medical Man, and he
+winked at me solemnly.
+
+
+
+
+ III.
+ The Time Traveller Returns
+
+
+I think that at that time none of us quite believed in the Time
+Machine. The fact is, the Time Traveller was one of those men who are
+too clever to be believed: you never felt that you saw all round him;
+you always suspected some subtle reserve, some ingenuity in ambush,
+behind his lucid frankness. Had Filby shown the model and explained the
+matter in the Time Traveller’s words, we should have shown _him_ far
+less scepticism. For we should have perceived his motives: a
+pork-butcher could understand Filby. But the Time Traveller had more
+than a touch of whim among his elements, and we distrusted him. Things
+that would have made the fame of a less clever man seemed tricks in his
+hands. It is a mistake to do things too easily. The serious people who
+took him seriously never felt quite sure of his deportment; they were
+somehow aware that trusting their reputations for judgment with him was
+like furnishing a nursery with eggshell china. So I don’t think any of
+us said very much about time travelling in the interval between that
+Thursday and the next, though its odd potentialities ran, no doubt, in
+most of our minds: its plausibility, that is, its practical
+incredibleness, the curious possibilities of anachronism and of utter
+confusion it suggested. For my own part, I was particularly preoccupied
+with the trick of the model. That I remember discussing with the
+Medical Man, whom I met on Friday at the Linnæan. He said he had seen a
+similar thing at Tübingen, and laid considerable stress on the
+blowing-out of the candle. But how the trick was done he could not
+explain.
+
+The next Thursday I went again to Richmond—I suppose I was one of the
+Time Traveller’s most constant guests—and, arriving late, found four or
+five men already assembled in his drawing-room. The Medical Man was
+standing before the fire with a sheet of paper in one hand and his
+watch in the other. I looked round for the Time Traveller, and—“It’s
+half-past seven now,” said the Medical Man. “I suppose we’d better have
+dinner?”
+
+“Where’s——?” said I, naming our host.
+
+“You’ve just come? It’s rather odd. He’s unavoidably detained. He asks
+me in this note to lead off with dinner at seven if he’s not back. Says
+he’ll explain when he comes.”
+
+“It seems a pity to let the dinner spoil,” said the Editor of a
+well-known daily paper; and thereupon the Doctor rang the bell.
+
+The Psychologist was the only person besides the Doctor and myself who
+had attended the previous dinner. The other men were Blank, the Editor
+aforementioned, a certain journalist, and another—a quiet, shy man with
+a beard—whom I didn’t know, and who, as far as my observation went,
+never opened his mouth all the evening. There was some speculation at
+the dinner-table about the Time Traveller’s absence, and I suggested
+time travelling, in a half-jocular spirit. The Editor wanted that
+explained to him, and the Psychologist volunteered a wooden account of
+the “ingenious paradox and trick” we had witnessed that day week. He
+was in the midst of his exposition when the door from the corridor
+opened slowly and without noise. I was facing the door, and saw it
+first. “Hallo!” I said. “At last!” And the door opened wider, and the
+Time Traveller stood before us. I gave a cry of surprise. “Good
+heavens! man, what’s the matter?” cried the Medical Man, who saw him
+next. And the whole tableful turned towards the door.
+
+He was in an amazing plight. His coat was dusty and dirty, and smeared
+with green down the sleeves; his hair disordered, and as it seemed to
+me greyer—either with dust and dirt or because its colour had actually
+faded. His face was ghastly pale; his chin had a brown cut on it—a cut
+half-healed; his expression was haggard and drawn, as by intense
+suffering. For a moment he hesitated in the doorway, as if he had been
+dazzled by the light. Then he came into the room. He walked with just
+such a limp as I have seen in footsore tramps. We stared at him in
+silence, expecting him to speak.
+
+He said not a word, but came painfully to the table, and made a motion
+towards the wine. The Editor filled a glass of champagne, and pushed it
+towards him. He drained it, and it seemed to do him good: for he looked
+round the table, and the ghost of his old smile flickered across his
+face. “What on earth have you been up to, man?” said the Doctor. The
+Time Traveller did not seem to hear. “Don’t let me disturb you,” he
+said, with a certain faltering articulation. “I’m all right.” He
+stopped, held out his glass for more, and took it off at a draught.
+“That’s good,” he said. His eyes grew brighter, and a faint colour came
+into his cheeks. His glance flickered over our faces with a certain
+dull approval, and then went round the warm and comfortable room. Then
+he spoke again, still as it were feeling his way among his words. “I’m
+going to wash and dress, and then I’ll come down and explain things....
+Save me some of that mutton. I’m starving for a bit of meat.”
+
+He looked across at the Editor, who was a rare visitor, and hoped he
+was all right. The Editor began a question. “Tell you presently,” said
+the Time Traveller. “I’m—funny! Be all right in a minute.”
+
+He put down his glass, and walked towards the staircase door.
diff --git a/user/about.c b/user/about.c
new file mode 100644
index 0000000..a26e2c5
--- /dev/null
+++ b/user/about.c
@@ -0,0 +1,13 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int main() {
+	printf("Welcome to Kailash OS!\n");
+	printf("-------------------------------------\n");
+	printf("Author: Kailash Turimella\n");
+	printf("USF Username: kturimella\n");
+	printf("Preferred Name: Kailash\n");
+
+	exit(0);
+}
diff --git a/user/benchmark.c b/user/benchmark.c
new file mode 100644
index 0000000..ddfd42d
--- /dev/null
+++ b/user/benchmark.c
@@ -0,0 +1,40 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int main(int argc, char *argv[]) {
+	if (argc < 2) {
+		fprintf(2, "Usage: %s <program> [args...]\n", argv[0]);
+		exit(1);
+	}
+
+	uint64 start = clock();
+
+	int pid = fork();
+	if (pid < 0) {
+		fprintf(2, "benchmark: fork failed\n");
+		exit(1);
+	}
+	if (pid == 0) {
+		exec(argv[1], &argv[1]);
+		fprintf(2, "benchmark: exec %s failed\n", argv[1]);
+		exit(1);
+	}
+
+	int status;
+	int counter;
+	
+	if (wait2(&status, &counter) < 0) {
+		fprintf(2, "benchmark: wait2 failed\n");
+		exit(1);
+	}
+
+	uint64 end = clock();
+	uint64 time_taken = end - start;
+	uint64 time_taken_ms = time_taken / 1000000ULL; 
+
+	printf("Benchmark Complete\n");
+	printf("Time Elapsed: %d ms\n", (int)time_taken_ms);
+	printf("System Calls: %d\n", (int)counter);
+	exit(0);
+}
diff --git a/user/broken.c b/user/broken.c
new file mode 100644
index 0000000..779f9ed
--- /dev/null
+++ b/user/broken.c
@@ -0,0 +1,324 @@
+/**
+ * @file broken.c
+ * @author mmalensek
+ *
+ * This program contains a series of buggy, broken, or strange C functions for
+ * you to ponder. Your job is to analyze each function, fix whatever bugs the
+ * functions might have, and then explain what went wrong. Sometimes the
+ * compiler will give you a hint.
+ *
+ *  ____________
+ * < Good luck! >
+ *  ------------
+ *      \   ^__^
+ *       \  (oo)\_______
+ *          (__)\       )\/\
+ *              ||----w |
+ *              ||     ||
+ */
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+
+static int func_counter = 1;
+#define FUNC_START() printf("\n\n%d.) %s\n", func_counter++, __func__);
+
+#pragma GCC diagnostic ignored "-Waggressive-loop-optimizations"
+#pragma GCC diagnostic ignored "-Wdangling-pointer"
+#pragma GCC diagnostic ignored "-Wformat-overflow"
+
+/**
+ * This code example was taken from the book 'Mastering C Pointers,' one of the
+ * not so good ways to learn pointers. It was trying to demonstrate how to print
+ * 'BNGULAR'... with pointers...? Maybe?
+ *
+ * (1) Fix the problem.
+ * (2) Explain what's wrong with this code:
+ *      String literals are stored in read only memory
+ *      '66' in this example is 'B'. What we can do is set a[0] = 'B' to replace the first char in the string.
+ */
+void
+angular(void)
+{
+  FUNC_START();
+
+  char a[] = "ANGULAR";
+  a[0] = 'B';
+  printf("%s\n", a);
+}
+
+/**
+ * This function is the next step after 'Hello world' -- it takes user input and
+ * prints it back out! (Wow).
+ *
+ * But, unfortunately, it doesn't work.
+ *
+ * (1) Fix the problem.
+ * (2) Explain what's wrong with this code:
+ *
+ *  The main problem for this one is that we have to allocate space
+ 	for the string. I tried to change gets to fgets but I don't think 
+ 	that works because using stdio.h didn't work.
+ 
+ */
+void
+greeter(void)
+{
+  FUNC_START();
+
+  char name[128];
+
+  printf("Please enter your name: ");
+  gets(name, 128);
+
+  // Remove newline character
+  char *p = name;
+  for ( ; *p != '\n' && *p != 0; p++) { }
+  *p = '\0';
+
+  printf("Hello, %s!\n", name);
+}
+
+/**
+ * This code isn't so much broken, but more of an exercise in understanding how
+ * C data types are represented in memory.
+ *
+ * (1) Fill in your guesses below to see if you can get all 6 correct on the
+ *     first try.
+ * (2) Explain *WHY* you get the sizes you do for each of the 6 entries.
+ *     sizeof(int) and sizeof(float) are fairly straightforward.
+
+ 	A char is always 1. Both ints and floats are 4. 
+ 	things is 48 because it is an array of 12 ints. so 12 x 4 = 48
+ 	'A' is an int so thats why its 4 bytes.
+ 	"A" is a string literal so it is 2 bytes. The null terminator "\0" is included in there.
+ *
+ */
+#define SIZE_CHECK(sz, guess) (sz), sz == guess ? "Right!" : "Wrong!"
+void
+sizer(void)
+{
+  FUNC_START();
+
+  int guesses[] = {1, 4, 4, 48, 4, 2 }; // fill in 6 guesses here
+  if (sizeof(guesses) / sizeof(int) != 6) {
+    printf("Please enter a guess for each of the sizes below.\n");
+    printf("Example: guesses[] = { 1, 4, 0, 0, 0, 0 }\n");
+    printf("would mean sizeof(char) == 1, sizeof(int) == 4, and so on");
+    return;
+  }
+
+  int things[12] = { 0 };
+  printf("sizeof(char)   = %ld\t[%s]\n", SIZE_CHECK(sizeof(char), guesses[0]));
+  printf("sizeof(int)    = %ld\t[%s]\n", SIZE_CHECK(sizeof(int), guesses[1]));
+  printf("sizeof(float)  = %ld\t[%s]\n", SIZE_CHECK(sizeof(float), guesses[2]));
+  printf("sizeof(things) = %ld\t[%s]\n", SIZE_CHECK(sizeof(things), guesses[3]));
+  printf("sizeof('A')    = %ld\t[%s]\n", SIZE_CHECK(sizeof('A'), guesses[4]));
+  printf("sizeof(\"A\")    = %ld\t[%s]\n", SIZE_CHECK(sizeof("A"), guesses[5]));
+}
+
+/**
+ * This 'useful' function prints out an array of integers with their indexes, or
+ * at least tries to. It even has a special feature where it adds '12' to the
+ * array.
+ *
+ * (1) Fix the problem.
+ * (2) Explain what's wrong with this code:
+ *
+ *   One problem I found is that the loop is until < 1000, which exceeds the size we set for
+     the stuff array which is 100. 
+     Another problem or inconvinience is the 14[stuff + 1] = 12. At first I didn't understand it,
+     but after searching online what it means. It basically just sets 12 to index 15. 
+ */
+void
+displayer(void)
+{
+  FUNC_START();
+
+  int stuff[100] = { 0 };
+
+  /* Can you guess what the following does without running the program? */
+  /* Rewrite it so it's easier to read. */
+  stuff[15] = 12;
+
+  for (int i = 0; i < 100; ++i) {
+    printf("%d: %d\n", i, stuff[i]);
+  }
+}
+
+/**
+ * Adds up the contents of an array and prints the total. Unfortunately the
+ * total is wrong! See main() for the arguments that were passed in.
+ *
+ * (1) Fix the problem.
+ * (2) Explain what's wrong with this code:
+ *
+ *   The problem is that sizeof(arr) doesn't work as intended. It wouldn't get to the 
+     end of the loop. To fix it I changed the function call so we can get the correct size of
+     array is use that to loop through.
+ */
+void
+adder(int *arr, int n)
+{
+  FUNC_START();
+
+  int total = 0;
+
+  for (int i = 0; i < n; ++i) {
+  	total += arr[i];
+  }
+
+  printf("Total is: %d\n", total);
+}
+
+/**
+ * This function is supposed to be somewhat like strcat, but it doesn't work.
+ *
+ * (1) Fix the problem.
+ * (2) Explain what's wrong with this code:
+ *	The problem is that it returns a pointer to a local array. When the function returns, it finishes.
+ 	To fix we use malloc to allocate it on the heap.
+ *   
+ */
+char *
+suffixer(char *a, char *b)
+{
+  FUNC_START();
+
+  char *buf = malloc(strlen(a) + strlen(b) + 1);
+  if (!buf) return 0;
+  
+  char *buf_start = buf;
+  
+  strcpy(buf, a);
+  strcpy(buf + strlen(a), b);
+  return buf_start;
+
+}
+
+/**
+ * This is an excerpt of Elon Musk's Full Self Driving code. Unfortunately, it
+ * keeps telling people to take the wrong turn. Figure out how to fix it, and
+ * explain what's going on so Elon can get back to work on leaving Earth for
+ * good.
+ *
+ * (1) Fix the problem.
+ * (2) Explain what's wrong with this code:
+ *
+ *   One problem is that in the if statement we aren't checking if its actually
+     true or not. So we have to add == 0 for it to work. The whole string comparison
+     part is also not needed.
+
+     There is also 2 overflow issues. 
+ */
+void
+driver(void)
+{
+  FUNC_START();
+
+  char street1[10] = { "fulton" };
+  char street2[10] = { "gomery" };
+  char street3[10] = { "piedmont" };
+  char street4[10] = { "baker" };
+  char street5[10] = { "haight" };
+
+  if (strcmp(street1, street2) == 0) {
+    char *new_name = "saint agnew ";
+    memcpy(street4, new_name, strlen(new_name));
+  }
+
+  printf("Welcome to TeslaOS 0.1!\n");
+  printf("Calculating route...\n");
+  printf("Turn left at the intersection of %s and %s.\n", street5, street3);
+}
+
+/**
+ * This function tokenizes a string by space, sort of like a basic strtok or
+ * strsep. It has two subtle memory bugs for you to find.
+ *
+ * (1) Fix the problem.
+ * (2) Explain what's wrong with this code:
+ *
+ *   One problem was is a size bug. the malloc allocates a byte too few
+ 	 so strcpy(line, str) overflows.
+ 	 Once the scan hits '\0', if it advances it would go past the buffer.
+ 	 
+ */
+void
+tokenizer(void)
+{
+  FUNC_START();
+
+  char *str = "Hope was a letter I never could send";
+  char *line = malloc(strlen(str) + 1);
+  char *base = line;
+  char *c = line;
+
+  strcpy(line, str);
+
+  while (*c != '\0') {
+
+    for ( ; *c != ' ' && *c != '\0'; c++) {
+      // find the next space (or end of string)
+    }
+
+	if (*c == '\0') {
+		printf("%s\n", line);
+		break;
+	}
+	
+    *c = '\0';
+    printf("%s\n", line);
+
+    line = c + 1;
+    c = line;
+  }
+
+  free(base);
+}
+
+/**
+* This function should print one thing you like about C, and one thing you
+* dislike about it. Assuming you don't mess up, there will be no bugs to find
+* here!
+*/
+void
+finisher(void)
+{
+  FUNC_START();
+
+  // TODO
+   printf("Something I like about C is how you can control much more about how everything works.\n");
+   printf("Something I don't like is that having a lot more control means more stuff can go wrong :( ");
+}
+
+int
+main(void)
+{
+  printf("Starting up!");
+
+
+  angular();
+
+  greeter();
+
+  sizer();
+
+  displayer();
+
+  int nums[] = { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512 };
+  adder(nums, sizeof(nums) / sizeof(nums[0]));
+
+  char *result = suffixer("kayak", "ing");
+  printf("Suffixed: %s\n", result);
+
+  driver();
+
+  tokenizer();
+
+  finisher();
+
+  return 0;
+}
diff --git a/user/catlines.c b/user/catlines.c
new file mode 100644
index 0000000..9de4315
--- /dev/null
+++ b/user/catlines.c
@@ -0,0 +1,40 @@
+#include "kernel/fcntl.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+fgets7(char *buf, int max, int fd)
+{
+  int i, cc;
+  char c;
+
+  for (i = 0; i + 1 < max; ) {
+    cc = read(fd, &c, 1);
+    if(cc < 1)
+      break;
+    buf[i++] = c;
+    if(c == '\n' || c == '\r')
+      break;
+  }
+  buf[i] = '\0';
+  return i;
+}
+
+int
+main(int argc, char *argv[])
+{
+  if (argc <= 1) {
+    fprintf(2, "Usage: %s filename\n", argv[0]);
+    return 1;
+  }
+
+  int fd = open(argv[1], O_RDONLY);
+  char buf[128];
+  int line_count = 0;
+  while (fgets7(buf, 128, fd) > 0 ) {
+    printf("Line %d: %s", line_count++, buf);
+  }
+
+  return 0;
+}
diff --git a/user/clear.c b/user/clear.c
new file mode 100644
index 0000000..b54b651
--- /dev/null
+++ b/user/clear.c
@@ -0,0 +1,8 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+int
+main(void) {
+	write(1, "\x1b[2J\x1b[H", 7);
+	exit(0);
+}
diff --git a/user/clock.c b/user/clock.c
new file mode 100644
index 0000000..627a700
--- /dev/null
+++ b/user/clock.c
@@ -0,0 +1,13 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(void)
+{
+	uint64 ns = clock();                   // call the clock function
+	uint64 sec64 = ns / 1000000000ULL;     // convert to seconds
+	printf("%d\n", (int)sec64);
+	exit(0);
+ 
+}
diff --git a/user/fnr.c b/user/fnr.c
new file mode 100644
index 0000000..140ecb2
--- /dev/null
+++ b/user/fnr.c
@@ -0,0 +1,29 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+int main(int argc, char *argv[]) {
+  char *line = malloc(512);
+  while (getline(&line, 512, 0) > 0) {
+    for (int i = 1; i < argc; i += 2) {
+      char *find = argv[i];
+      char *repl = argv[i + 1];
+      uint find_len = strlen(find);
+      if (strlen(line) < find_len) {
+        continue;
+      }
+      for (int j = 0; j < strlen(line) - find_len; ++j) {
+        char *p = line + j;
+        char *q = find;
+        int k;
+        for (k = 0; *p && *p == *q && k < find_len; ++k) {
+          p++, q++;
+        }
+        if (k == find_len) {
+          memcpy(line + j, repl, find_len);
+        }
+      }
+    }
+    printf("%s", line);
+  }
+  return 0;
+}
diff --git a/user/freemem.c b/user/freemem.c
new file mode 100644
index 0000000..0c87fb5
--- /dev/null
+++ b/user/freemem.c
@@ -0,0 +1,11 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(void)
+{
+  int k = freemem();
+  printf("%d KiB\n", k);
+  exit(0);
+}
diff --git a/user/leetify.c b/user/leetify.c
new file mode 100644
index 0000000..b18fc2b
--- /dev/null
+++ b/user/leetify.c
@@ -0,0 +1,154 @@
+/**
+ * @file leetify.c
+ *
+ * Scaffolding to create an amazing l337speak generator using only external
+ * commands combined with pipelines.
+ */
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fcntl.h"
+
+/**
+ * Represents a command in a pipeline.
+ * Note that EITHER stdout_pipe can be true, or a stdout_file can be set.
+ *
+ * - tokens Array of strings that describe the command to run
+ * - stdout_pipe set to true if this command's output should be written to pipe
+ * - stdout_file set to a file name if this command's output should be written
+ *     to a file
+ */
+struct command {
+  char **tokens;
+  int stdout_pipe;
+  char *stdout_file;
+};
+
+void
+execute_pipeline(struct command *cmds, int n)
+{
+
+   // go through all the commands
+   for (int i = 0; i < n - 1; i++) {
+
+   	int p[2]; // p[0] stdin, p[1] stdout
+   	if (pipe(p) < 0) {
+   		fprintf(2, "pipe failed\n");
+   		exit(1);
+   	}
+   	
+	int pid = fork();
+	if (pid < 0) {
+		fprintf(2, "fork failed\n");
+		exit(1);
+	}
+	
+   	if (pid == 0) {
+   		// child
+
+   		// redirect stdout to write end of pipe
+   		close(p[0]); // close read
+   		close(1);    // redirect stdout -> pipe write end
+   		dup(p[1]);
+   		close(p[1]);
+
+   		// exec
+   		exec(cmds[i].tokens[0], cmds[i].tokens);
+
+   		fprintf(2, "exec %s failed\n", cmds[i].tokens[0]);
+   		exit(1);
+   	} else {
+   		// parent
+
+   		// close write end of pipe
+   		close(p[1]);
+
+   		// redirect stdin
+   		close(0);
+   		dup(p[0]);
+
+   		// close copy of the read end
+   		close(p[0]);
+   		
+   	}
+   }
+    struct command *final_command = &cmds[n-1];
+    if (final_command->stdout_file) {
+    	int fd = open(final_command->stdout_file, O_CREATE | O_WRONLY | O_TRUNC);
+    	if (fd < 0) {
+    		fprintf(2, "open failed for %s\n", final_command->tokens[0]);
+    		exit(1);
+    	}
+    	close(1);
+    	dup(fd);
+    	close(fd);
+    }
+
+    exec(final_command->tokens[0], final_command->tokens);
+    fprintf(2, "exec failed: %s\n", final_command->tokens[0]);
+    exit(1);
+   
+}
+
+int
+main(int argc, char *argv[])
+{
+  char *input_file = (char *)0;
+  char *output_file = (char *) 0;
+
+  if (argc < 2 || argc > 3) {
+    printf("Usage: %s file-to-leetify [output-file]\n", argv[0]);
+    return 1;
+  }
+
+  input_file = argv[1];
+
+  if (argc == 3) {
+    output_file = argv[2];
+  }
+
+  printf("Input file: %s\n", input_file);
+  if (output_file) {
+    printf("Writing to output file: %s\n", output_file);
+  }
+
+  // cat input file
+  char *command1[] = { "cat", input_file, (char *)0 };
+  // tolower
+  char *command2[] = { "tolower", (char *)0 };
+  // fnr 
+  char *command3[] = { "fnr", "the", "teh", "a", "4", "e", "3", "i", "!", (char *)0 };
+  // fnr 2
+  char *command4[] = { "fnr", "l", "1", "o", "0", "s", "5", (char *)0 };
+
+  struct command cmds[4] = { 0 };
+  cmds[0].tokens = command1;  /* What this command runs */
+  cmds[0].stdout_pipe = 1;
+  cmds[0].stdout_file = (char *)0; /* This command is not writing to a file. */
+
+  cmds[1].tokens = command2;
+  cmds[1].stdout_pipe = 1;
+  cmds[1].stdout_file = (char *)0; /* This command's output goes to a pipe. */
+
+  cmds[2].tokens = command3;
+  cmds[2].stdout_pipe = 1;
+  cmds[2].stdout_file = (char *)0;
+
+  cmds[3].tokens = command4;
+  cmds[3].stdout_pipe = 0; /* Last command so set stdout_pipe = false */
+  cmds[3].stdout_file = output_file;
+
+  int pid = fork();
+  if (pid == -1) {
+    fprintf(2, "Fork failed\n");
+    return 1;
+  } else if (pid == 0) {
+    execute_pipeline(cmds, 4);
+  } else {
+    int status;
+    wait(&status);
+  }
+
+  return 0;
+}
diff --git a/user/mmap.c b/user/mmap.c
new file mode 100644
index 0000000..d3f8523
--- /dev/null
+++ b/user/mmap.c
@@ -0,0 +1,17 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(void)
+{
+  char *p = (char*)mmap();
+  if (!p) {
+    printf("mmap failed\n");
+    exit(1);
+  }
+
+  strcpy(p, "hello from mmap");
+  printf("%s\n", p);
+  exit(0);
+}
diff --git a/user/mmaptest.c b/user/mmaptest.c
new file mode 100644
index 0000000..f3477d9
--- /dev/null
+++ b/user/mmaptest.c
@@ -0,0 +1,53 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(void)
+{
+  char *a = mmap();   
+  char *b = mmap();    
+  char *c = mmap();   
+
+  strcpy(a, "a: hello");
+  strcpy(b, "b: world");
+  strcpy(c, "c: original");
+
+  printf("parent original:\n%s\n%s\n%s\n\n", a, b, c);
+
+
+  int pid = fork();
+
+  if(pid == 0){
+ 
+    printf("child sees after fork:\n%s\n%s\n%s\n\n", a, b, c);
+
+    // child modifies first two pages
+    strcpy(a, "a: spurs");
+    strcpy(b, "b: child changed world");
+
+	// forks and makes another child (grandchild)
+    int pid2 = fork();
+    if(pid2 == 0){
+      printf("grandchild sees:\n%s\n%s\n%s\n\n", a, b, c);
+
+      // grandchild modifies the 3rd page
+      strcpy(c, "C: grandchild updated this");
+
+      printf("grandchild done.\n");
+      exit(0);
+    }
+
+    // child waits for grandchild to finish updating page C
+    wait(0);
+
+    printf("child after grandchild:\n%s\n%s\n%s\n\n", a, b, c);
+    exit(0);
+  }
+  
+  wait(0);
+
+  printf("parent final:\n%s\n%s\n%s\n\n", a, b, c);
+
+  exit(0);
+}
diff --git a/user/mt70.c b/user/mt70.c
new file mode 100644
index 0000000..4776483
--- /dev/null
+++ b/user/mt70.c
@@ -0,0 +1,49 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+#pragma GCC diagnostic ignored "-Wunused-variable"
+
+int main(void)
+{
+//  malloc_setfsm(FSM_FIRST_FIT);
+
+  char *a = malloc(132);
+  char *b = malloc(42);  /* Will be deleted */
+  char *c = malloc(132);
+  char *d = malloc(132); /* Will be deleted */
+  char *e = malloc(132);
+  char *f = malloc(3132);
+
+  /* These allocations total 4096 bytes after alignment is included. */
+
+  malloc_name(a, "A");
+  malloc_name(b, "B");
+  malloc_name(c, "C");
+  malloc_name(d, "D");
+  malloc_name(e, "E");
+  malloc_name(f, "F");
+
+  free(b);
+  free(d);
+
+  /**
+   * The following allocation will choose:
+   * - First fit: free space at the end of the page (unnamed, no variable)
+   * - Best fit:  B
+   * - Worst fit: D
+   */
+  char *g = malloc(42);
+
+  malloc_name(g, "G");
+
+  malloc_print();
+
+  /**
+   * Things to check:
+   * - correct alignment (evenly divisible by 16)
+   * - free block sizes are correct (make sure not off by one)
+   * - end of last block's memory address - first address = 4096
+   */
+
+  return 0;
+}
diff --git a/user/mt80.c b/user/mt80.c
new file mode 100644
index 0000000..4776483
--- /dev/null
+++ b/user/mt80.c
@@ -0,0 +1,49 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+#pragma GCC diagnostic ignored "-Wunused-variable"
+
+int main(void)
+{
+//  malloc_setfsm(FSM_FIRST_FIT);
+
+  char *a = malloc(132);
+  char *b = malloc(42);  /* Will be deleted */
+  char *c = malloc(132);
+  char *d = malloc(132); /* Will be deleted */
+  char *e = malloc(132);
+  char *f = malloc(3132);
+
+  /* These allocations total 4096 bytes after alignment is included. */
+
+  malloc_name(a, "A");
+  malloc_name(b, "B");
+  malloc_name(c, "C");
+  malloc_name(d, "D");
+  malloc_name(e, "E");
+  malloc_name(f, "F");
+
+  free(b);
+  free(d);
+
+  /**
+   * The following allocation will choose:
+   * - First fit: free space at the end of the page (unnamed, no variable)
+   * - Best fit:  B
+   * - Worst fit: D
+   */
+  char *g = malloc(42);
+
+  malloc_name(g, "G");
+
+  malloc_print();
+
+  /**
+   * Things to check:
+   * - correct alignment (evenly divisible by 16)
+   * - free block sizes are correct (make sure not off by one)
+   * - end of last block's memory address - first address = 4096
+   */
+
+  return 0;
+}
diff --git a/user/mt90.c b/user/mt90.c
new file mode 100644
index 0000000..c126462
--- /dev/null
+++ b/user/mt90.c
@@ -0,0 +1,90 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+#pragma GCC diagnostic ignored "-Wunused-variable"
+
+void
+merge_test(void)
+{
+  char *start = sbrk(0);
+  printf("Starting address: %p\n\n", start);
+
+  void *a = malloc(532);   malloc_name(a, "A");
+  void *b = malloc(326);   malloc_name(b, "B");
+  void *c = malloc(282);   malloc_name(c, "C");
+  void *d = malloc(1032);  malloc_name(d, "D");
+  void *e = malloc(432);   malloc_name(e, "E");
+
+  free(b);
+  free(c);
+  free(a);
+  free(d);
+  free(e);
+
+  malloc_print();
+
+  printf("\n\n");
+
+  void *f = malloc(632);   malloc_name(f, "F");
+  void *g = malloc(182);   malloc_name(f, "G");
+  void *h = malloc(9928);  malloc_name(f, "H");
+
+  free(f);
+  free(g);
+  free(h);
+
+  malloc_print();
+
+  char *end = sbrk(0);
+  printf("\n\nEnding address: %p\n", end);
+
+  if (start == end) {
+    printf("Success! start == end!\n");
+  }
+}
+
+void
+realloc_test(void)
+{
+  char *a = malloc(532);    malloc_name(a, "A");
+  void *b = malloc(326);    malloc_name(b, "B");
+  void *c = malloc(282);    malloc_name(c, "C");
+  void *d = malloc(1032);   malloc_name(d, "D");
+  void *e = malloc(432);    malloc_name(e, "E");
+
+  /* Does not actually need to be resized */
+  a = realloc(a, 542);      malloc_name(a, "R1");
+
+  /* No room, must free + allocate new */
+  c = realloc(c, 9632);      malloc_name(c, "R2");
+
+  /* Now that 'c' is free, we can expand 'b' into it */
+  b = realloc(b, 632);      malloc_name(b, "R3");
+
+  /* Expand into free space at the end of the region. This will produce a new
+     * free block out of the remaining space */
+  e = realloc(e, 1312);      malloc_name(e, "R4");
+
+  /* Shrink 'd' down to make a new free block */
+  d = realloc(d, 832);      malloc_name(d, "R5");
+
+  /* Shrink 'd' one more time to make sure that the two neighboring free
+     * blocks get merged back together */
+  d = realloc(d, 632);      malloc_name(d, "R6");
+
+  malloc_print();
+}
+
+int
+main(void)
+{
+  printf("---- MERGE TEST ----\n");
+  merge_test();
+  printf("\n\n");
+
+  printf("---- REALLOC TEST ----\n");
+  realloc_test();
+  printf("\n\n");
+
+  return 0;
+}
diff --git a/user/nice.c b/user/nice.c
new file mode 100644
index 0000000..fe0b3e6
--- /dev/null
+++ b/user/nice.c
@@ -0,0 +1,32 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int main(int argc, char *argv[]) {
+  if (argc < 3) {
+    fprintf(2, "usage: nice <0..3> cmd [args...]\n");
+    exit(1);
+  }
+  int n = atoi(argv[1]);
+  if (n < 0)
+  	n = 0;
+  if (n > 3)
+  	n = 3;
+
+  int pid = fork();
+
+  if (pid < 0) {
+  	fprintf(2, "nice: fork failed\n");
+  	exit(1);
+  }
+
+  if (pid == 0) {
+  	nice(n);
+  	exec(argv[2], &argv[2]);
+  	fprintf(2, "nice: exec %s failed\n", argv[2]);
+  	exit(1);
+  }
+
+  wait(0);
+  exit(0);
+}
diff --git a/user/opt_cat.c b/user/opt_cat.c
new file mode 100644
index 0000000..ed4b763
--- /dev/null
+++ b/user/opt_cat.c
@@ -0,0 +1,59 @@
+#include "kernel/fcntl.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+static int
+fgets3(char *out, int max, int fd)
+{
+  enum { CAP = 8192 };
+  static char storage[CAP];
+  static int  r = 0, w = 0;
+  int outi = 0;
+
+  for (;;) {
+    if (r >= w) {
+      r = w = 0;
+      int n = read(fd, storage, CAP);
+      if (n <= 0) {
+        if (outi == 0) return 0;
+        out[outi] = '\0';
+        return outi;
+      }
+      w = n;
+    }
+
+    while (r < w && outi + 1 < max) {
+      char c = storage[r++];
+      out[outi++] = c;
+      if (c == '\n' || c == '\r') {
+        out[outi] = '\0';
+        return outi;
+      }
+    }
+
+    if (outi + 1 >= max) {
+      out[outi] = '\0';
+      return outi;
+    }
+  }
+}
+
+
+int
+main(int argc, char *argv[])
+{
+  if (argc <= 1) {
+    fprintf(2, "Usage: %s filename\n", argv[0]);
+    return 1;
+  }
+
+  int fd = open(argv[1], O_RDONLY);
+  char buf[128];
+  int line_count = 0;
+  while (fgets3(buf, 128, fd) > 0 ) {
+    printf("Line %d: %s", line_count++, buf);
+  }
+
+  return 0;
+}
diff --git a/user/pwd.c b/user/pwd.c
new file mode 100644
index 0000000..165ab8b
--- /dev/null
+++ b/user/pwd.c
@@ -0,0 +1,11 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+int
+main(void)
+{
+  char buf[128];
+  getcwd(buf, 128);
+  printf("%s\n", buf);
+  return 0;
+}
diff --git a/user/reboot.c b/user/reboot.c
new file mode 100644
index 0000000..a44da64
--- /dev/null
+++ b/user/reboot.c
@@ -0,0 +1,14 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char **argv)
+{
+	printf("Rebooting...\n");
+	reboot();
+
+	// error message just in case
+	fprintf(2, "reboot failed!\n");
+	exit(1);
+}
diff --git a/user/shell.c b/user/shell.c
new file mode 100644
index 0000000..f315f55
--- /dev/null
+++ b/user/shell.c
@@ -0,0 +1,389 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fcntl.h"
+
+int fgets(char *buf, unsigned int max, int fd);
+
+uint
+strspn(const char *str, const char *chars)
+{
+  uint i, j;
+  for (i = 0; str[i] != '\0'; i++) {
+    for (j = 0; chars[j] != str[i]; j++) {
+      if (chars[j] == '\0')
+        return i;
+    }
+  }
+  return i;
+}
+
+uint
+strcspn(const char *str, const char *chars)
+{
+  const char *p, *sp;
+  char c, sc;
+  for (p = str;;) {
+    c = *p++;
+    sp = chars;
+    do {
+      if ((sc = *sp++) == c) {
+        return (p - 1 - str);
+      }
+    } while (sc != 0);
+  }
+}
+
+char
+*next_token(char **str_ptr, const char *delim)
+{
+  if (*str_ptr == 0) {
+    return 0;
+  }
+
+  uint tok_start = strspn(*str_ptr, delim);
+  uint tok_end = strcspn(*str_ptr + tok_start, delim);
+
+  /* Zero length token. We must be finished. */
+  if (tok_end  == 0) {
+    *str_ptr = 0;
+    return 0;
+  }
+
+  /* Take note of the start of the current token. We'll return it later. */
+  char *current_ptr = *str_ptr + tok_start;
+
+  /* Shift pointer forward (to the end of the current token) */
+  *str_ptr += tok_start + tok_end;
+
+  if (**str_ptr == '\0') {
+    /* If the end of the current token is also the end of the string, we
+         * must be at the last token. */
+    *str_ptr = 0;
+  } else {
+    /* Replace the matching delimiter with a NUL character to terminate the
+         * token string. */
+    **str_ptr = '\0';
+
+    /* Shift forward one character over the newly-placed NUL so that
+         * next_pointer now points at the first character of the next token. */
+    (*str_ptr)++;
+  }
+
+  return current_ptr;
+}
+
+// helper func to just print the basic prompt
+static void print_prompt(int last_status, int cmd_num) {
+	char path[128];
+	int n = getcwd(path, sizeof(path));
+	if (n < 0) {
+		path[0] = '/'; path[1] = 0;
+	}
+	printf("[%d]-[%d]-[%s]$ ", last_status, cmd_num, path);
+}
+
+static int is_blank(const char *s) {
+	for (; *s; s++) {
+		if (*s!= ' ' && *s!= '\t' && *s!= '\n' && *s!= '\r') return 0;
+	}
+	return 1;
+}
+
+// helper fun to remove remove newliens and return characters
+static void strip_trailing_newline(char *buf, int *len_io) {
+	int len = *len_io;
+	while (len > 0 && (buf[len-1] == '\n' || buf[len-1] == '\r')) {
+		buf[--len] = 0;
+	}
+	*len_io = len;
+}
+
+// helper to check for comments and remove them
+static void remove_comment(char *buf) {
+	for (int i = 0; buf[i]; i++) {
+		if (buf[i] == '#') {
+			buf[i] = 0;
+			break;
+		}
+	}
+}
+
+#define MAX_HIST 100
+struct history_entry {
+	int num;
+	char line[256];
+	int duration_ms;
+};
+
+static struct history_entry hist[MAX_HIST];
+
+// method to add to the history
+static void add_history(const char *line, int cmd_num) {
+	if (!line || !*line) return;
+	int slot = (cmd_num - 1) % MAX_HIST;
+	hist[slot].num = cmd_num;
+
+	int i = 0;
+	for (; i < (int)sizeof(hist[slot].line) - 1 && line[i]; i++) {
+		hist[slot].line[i] = line[i];
+	}
+	hist[slot].line[i] = 0;
+}
+
+// actual history command
+static void history_command(int current_cmd_num, int show_time) {
+	int last_done = current_cmd_num - 1;   // last completed command
+	if (last_done < 1) return;
+
+	int first = last_done - MAX_HIST + 1;
+	if (first < 1) first = 1;
+
+	for (int n = first; n <= last_done; n++) {
+		int slot = (n - 1) % MAX_HIST;
+		if (hist[slot].num == n && hist[slot].line[0] != 0) {
+			if (show_time) {
+				printf("[%d|%dms] %s\n", hist[slot].num, hist[slot].duration_ms, hist[slot].line);
+			} else {
+				printf("%d %s\n", hist[slot].num, hist[slot].line);
+			}
+		}
+	}
+}
+
+// lookup in history with number arg
+static const char* hist_num(int num) {
+	if (num < 1) return 0;
+	int slot = (num - 1) % MAX_HIST;
+
+	// make sure that everything matches and line isn't empty
+	if (hist[slot].num == num && hist[slot].line[0] != 0) return hist[slot].line;
+
+	return 0;
+}
+
+// lookup in history with prefix arg
+static const char* hist_prefix(const char *prefix, int last_done) {
+	int prefix_len = 0;
+	while(prefix[prefix_len])
+		prefix_len++;
+
+	// go through all the commands 
+	// from newest to oldest
+	for (int n = last_done; n >= 1; n--) {
+		int slot = (n - 1) % MAX_HIST;
+
+		if (hist[slot].num != n || hist[slot].line[0] == 0) 
+			continue;
+		
+		const char *s = hist[slot].line;
+
+		// compare prefix against start of the command
+		int i = 0;
+		while (i < prefix_len && s[i] == prefix[i])
+			i++;
+
+		// if they match return the string
+		if (i == prefix_len)
+			return s;
+	}
+
+	return 0;
+}
+
+int
+main(int argc, char *argv[])
+{
+
+  // -1. print a prompt
+  //  0. get the user's command (stdin)
+  //  1. fork
+  //  2. exec
+  
+
+  int last_status = 0;  // 0 = success, 1 = fail
+  int cmd_num = 1; 
+  int scripting = 0;
+  int script_fd = -1;
+
+  if (argc > 1) {
+  	script_fd = open(argv[1], O_RDONLY);
+  	if (script_fd < 0) {
+  		fprintf(2, "shell: cannot open %s", argv[1]);
+  		exit(1);
+  	}
+  	scripting = 1;
+  }  
+  
+
+  while (1) {
+    if (!scripting) {
+    	print_prompt(last_status, cmd_num);
+    }
+   	
+    char buf[256];
+
+    int r;
+    if (scripting) {
+    	int i = 0;
+    	while (i + 1 < sizeof(buf)) {
+    		char c;
+    		r = read(script_fd, &c, 1);
+    		if (r < 1) {
+    			break;
+    		}
+    		buf[i++] = c;
+    		if (c == '\n')
+    			break;
+    	}
+    	buf[i] = 0;
+
+    	if (i == 0) {
+    		//fprintf(2, "shell: script EOF, exiting\n");
+    		exit(0);
+    	}
+    } else {
+    	if (gets(buf, sizeof(buf)) == 0) {
+    		printf("\n");
+    		exit(0);
+    	}
+    }
+
+
+	int got = strlen(buf);
+   
+	// remove "\n" and comments
+	strip_trailing_newline(buf, &got);
+	remove_comment(buf);
+	
+	// skip blank lines
+	if (is_blank(buf)) {
+		continue;
+	}
+
+	/*
+	Extra history commands:
+	1. "!" -> last command
+	2. "!5" -> command number 5
+	3. "!prefix" -> most recent command with the prefix
+	*/
+
+	if (buf[0] == '!') {
+		int last_done = cmd_num - 1;
+		const char *expanded = 0;
+
+		// the prev command
+		if (buf[1] == '!' && buf[2] == 0) {
+			expanded = hist_num(last_done);
+		} else if (buf[1] >= '0' && buf[1] <= '9') {
+			int n = 0;
+			for (int i = 1; buf[i] >= '0' && buf[i] <= '9'; i++) {
+				n = n * 10 + (buf[i] - '0');
+			}
+			expanded = hist_num(n);
+		} else {
+			// !prefix
+			expanded = hist_prefix(buf + 1, last_done);
+		}
+
+		if (!expanded) {
+			fprintf(2, "history: no match for '%s'\n", buf);
+			last_status = 1;
+			cmd_num++;
+			continue;
+		}
+
+		
+		int i = 0;
+		while (i < (int)sizeof(buf) - 1 && expanded[i]) {
+			buf[i] = expanded[i];
+			i++;
+		}
+		buf[i] = 0;
+
+		printf("%s\n", buf);
+	}
+
+	// record this command before executing so numbers align
+    add_history(buf, cmd_num);
+
+
+    char *args[32];
+    int tokens = 0;
+    char *next_tok = buf;
+    char *curr_tok;
+    /* Tokenize. */
+    while ((curr_tok = next_token(&next_tok, " \n\t\r")) != 0 && tokens < 31) {
+     // printf("Token: '%s'\n", curr_tok);
+      args[tokens++] = curr_tok;
+    }
+    args[tokens] = 0;
+    if (tokens == 0) {
+    	continue;
+    }
+
+
+    // built in commands
+    if (strcmp(args[0], "exit") == 0) {
+    	exit(0);
+    }
+
+	// history command
+    if (strcmp(args[0], "history") == 0) {
+    	int show_time = 0;
+    	if (tokens > 1 && strcmp(args[1], "-t") == 0)
+    		show_time = 1;
+    	history_command(cmd_num, show_time);
+    	last_status = 0;
+    	cmd_num++;
+    	continue;
+    }
+
+    
+    if (strcmp(args[0], "cd") == 0) {
+    	if (tokens < 2) {
+    		fprintf(2, "chdir: missing arg\n");
+    		last_status = 1;
+    	} else if (chdir(args[1]) < 0) {
+    		fprintf(2, "chdir: no file or directory found: %s\n", args[1]);
+    		last_status = 1;
+    	} else {
+    		last_status = 0;
+    	}
+    	cmd_num++;
+    	continue;
+    }
+
+    uint64 start = clock();
+
+    int pid = fork();
+    if (pid < 0 ) {
+      fprintf(2, "Fork failed");
+      last_status = 1;
+      cmd_num++;
+      continue;
+      
+    } else if (pid == 0) {
+      // child
+      // execute the command
+      exec(args[0], args);
+
+	  fprintf(2, "exec failed: %s\n", args[0]);
+	  exit(1);
+      
+    } else {
+      wait(0);
+      
+      uint64 end = clock();
+      uint64 diff = end - start;
+      int diff_ms = (int)(diff / 1000000ULL);
+
+      int slot = (cmd_num - 1) % MAX_HIST;
+      hist[slot].duration_ms = diff_ms;
+      
+      cmd_num++;
+    }
+  }
+
+  return 0;
+}
diff --git a/user/shutdown.c b/user/shutdown.c
new file mode 100644
index 0000000..418275a
--- /dev/null
+++ b/user/shutdown.c
@@ -0,0 +1,14 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char **argv)
+{
+	printf("Shutting down...\n");
+	shutdown();
+
+	// error message just in case
+	fprintf(2, "shutdown failed!\n");
+	exit(1);
+}
diff --git a/user/spinner.c b/user/spinner.c
new file mode 100644
index 0000000..0c70fd8
--- /dev/null
+++ b/user/spinner.c
@@ -0,0 +1,28 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+int
+main(int argc, char *argv[])
+{
+  if (argc <= 2) {
+    fprintf(2, "Usage: spinner name amount\n");
+    exit(1);
+  }
+
+  char *name = argv[1];
+  int amount = atoi(argv[2]);
+
+  int start = uptime();
+  for (int i = 0; i < amount; ++i) {
+    printf("%s", name);
+    for (int j = 0; j < 10000000; ++j) {
+      // wheee :-)
+    }
+  }
+  int end = uptime();
+
+  printf("\n[%s] has finished, %d work in %d ticks.\n",
+         name, amount, end - start);
+
+  exit(0);
+}
diff --git a/user/strace.c b/user/strace.c
new file mode 100644
index 0000000..f7a6cb8
--- /dev/null
+++ b/user/strace.c
@@ -0,0 +1,21 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char *argv[]) {
+	if(argc < 2) {
+		fprintf(2, "Usage: tracer command...\n");
+		exit(1);
+	}
+
+	if (fork() == 0) {
+		strace_on();
+		exec(argv[1], argv + 1);
+		fprintf(2, "tracer: exec %s failed\n", argv[1]);
+		exit(1);
+	}
+	wait(0);
+
+	exit(0);
+}
diff --git a/user/tolower.c b/user/tolower.c
new file mode 100644
index 0000000..55eb0a5
--- /dev/null
+++ b/user/tolower.c
@@ -0,0 +1,12 @@
+#include "kernel/types.h"
+#include "user/user.h"
+
+int main() {
+  for (int c = 0; read(0, &c, 1) > 0; ) {
+    if (c >= 'A' && c <= 'Z') {
+      c = c - 'A' + 'a';
+    }
+    write(1, &c, 1);
+  }
+  return 0;
+}
diff --git a/user/ulib.c b/user/ulib.c
index a2f5a20..82b1b3a 100644
--- a/user/ulib.c
+++ b/user/ulib.c
@@ -158,3 +158,69 @@ sbrklazy(int n) {
   return sys_sbrk(n, SBRK_LAZY);
 }
 
+// Reads contents of given file ('fd') to 'buf' of size 'max'.
+// Returns character's read, excluding null terminator.
+int
+fgets(char *buf, unsigned int max, int fd)
+{
+  int i, cc;
+  char c;
+
+  for(i=0; i+1 < max; ){
+    cc = read(fd, &c, 1);
+    if(cc < 1) {
+      return -1;
+    }
+    buf[i++] = c;
+    if(c == '\n' || c == '\r'){
+      break;
+    }
+  }
+
+  buf[i] = '\0';
+  return i;
+}
+
+// Like fgets, but dynamically allocates correct memory
+// to store the string.
+// Caller provides pointer to a malloced 'buf' and capacity ('size').
+// 'buf' points to NULL, a new buffer is allocated.
+// Returns characters read, excluding null terminator.
+int
+getline(char **buf, int size, int fd)
+{
+  int chars_read = 0;
+  int curr_read;
+
+  // initilize buffer if not already initilized  (size = 2, malloc space for a char + /0)
+  if (*buf == 0 || size < 2) {
+    free(*buf);	// in case buf was 1 (if null, does nothing)
+    *buf = malloc(2);
+    size = 2;
+  }
+
+  while ((curr_read = fgets(*buf + chars_read, size - chars_read, fd))) {
+
+    if (curr_read < 0) {  // error in fgets
+      return - 1;
+    }
+
+    chars_read += curr_read;
+
+    //resize
+    char *temp = malloc(size * 2);
+    memcpy(temp, *buf, chars_read + 1); // include null term
+    free(*buf);
+    *buf = temp;
+    size = size * 2;
+
+    // break if end of line/eof
+    char *last_char = *buf + (chars_read - 1);
+    if (strcmp(last_char, "\n") == 0 || strcmp(last_char, "\r") == 0) {
+      break;
+    }
+  }
+
+  return chars_read;
+}
+
diff --git a/user/umalloc.c b/user/umalloc.c
index 2ac6894..16c4bf3 100644
--- a/user/umalloc.c
+++ b/user/umalloc.c
@@ -3,88 +3,423 @@
 #include "user/user.h"
 #include "kernel/param.h"
 
-// Memory allocator by Kernighan and Ritchie,
-// The C programming Language, 2nd ed.  Section 8.7.
+#define NULL 0
+#define PAGE_SIZE 4096
+#define MIN_SPLIT_BLOCK_SIZE (sizeof(struct mem_block) + 16)
 
-typedef long Align;
 
-union header {
-  struct {
-    union header *ptr;
-    uint size;
-  } s;
-  Align x;
+#define NAME_LEN 16
+
+#define BLOCK_HEADER_SIZE sizeof(struct mem_block)
+
+
+/* If we haven't passed -DDEBUG=1 to gcc, then this will be set to 0: */
+#ifndef DEBUG
+#define DEBUG 1
+#endif
+
+
+// Real allocator block metadata
+struct mem_block {
+  char name[8];              
+  uint64 size;                                  
+  struct mem_block *next;    
+  struct mem_block *prev;    
 };
 
-typedef union header Header;
 
-static Header base;
-static Header *freep;
+struct mem_block *head;
+struct mem_block *tail;
+
+// Free space management algorithms
+enum {
+  FSM_FIRST_FIT = 0,
+  FSM_BEST_FIT  = 1,
+  FSM_WORST_FIT = 2,
+};
+
+static int current_fsm = FSM_FIRST_FIT; 
+
+// Our memory:
+// +----------+   <--- base
+// |          |
+// |          |
+// |          |   <--- bound
+// |          |
+// |          |
+// |          |
+// |          |
+// |          |
+// |          |
+// |          |
+// +----------+
+//
+// malloc -> ask kernel for more memory
+// free   -> tell kernel to shrink our memory
+//
+// "Hello Kernel, can I have 32 bytes of space please?"    (sbrk)
+// -> allocate 1 page of memory
+// -> hand us 32 bytes of it
+// "Hello Kernel, can I have 32 bytes of space please?"    (sbrk)
+// -> it would be bad to allocate another page here
+//      maybe the previous thing is not used anymore
+//      maybe we want to make use of the 4096 - 32 bytes left from the first
+//      page
+//
+//
+// So, our allocator is going to allocate *pages* of memory at a time.
+// One page can hold multiple blocks of memory:
+// +-------------------------------------------+
+// |     |             |       | |       |     | 1 page (4096 bytes)
+// +-------------------------------------------+
+//       ^             ^       ^ ^       ^
+
+// The 'size' of a block:
+// 1101 .... 0010 0000 0001  <- free
+// 1101 .... 1110 0000 0000  <- used
+//
+// Why we can do this:
+//  - We are going to round everything up so that sizes are multiples of 16
+//  - That means the smallest size we can have is 16 (0001 0000)
+//  - Note how the last 4 bits are never used... so we store the free bit there!
+
+// Get the block header from a data pointer
+struct mem_block* get_header(void* ptr) {
+    return (struct mem_block*)((char*)ptr - BLOCK_HEADER_SIZE);
+}
+
+static uint
+align16(uint size)
+{
+  return (size + 15) & ~0x0F;
+}
+
+//
+void set_used(struct mem_block *block)
+{
+  // turn off the least significant bit
+  block->size = block->size & (~0x01);
+}
+
+void set_free(struct mem_block *block)
+{
+  // turn on the least significant bit
+  block->size = block->size | 0x01;
+}
+
+int is_free(struct mem_block *block)
+{
+  // check whether the last bit is set or not
+  return block->size & 0x01;
+}
+
+uint get_size(struct mem_block *block)
+{
+  // ignore the free bit when retrieving the size
+  return block->size & (~0x01);
+}
+
+/* Given an existing block, this function should split it in two */
+// How this works:
+// Maybe we allocate 1 byte
+// That gets turned into 16 (that's our minimum size)
+// But then that gets turned into 4096 (our page size)
+struct mem_block *
+split(struct mem_block *block, uint total_sz)
+{
+  if (block == NULL) {
+    return NULL;
+  }
+
+  if (!is_free(block)) {
+    return NULL;
+  }
+
+  uint old_size = get_size(block);
+
+  // Don't split if remainder would be too small
+  if (old_size <= total_sz + MIN_SPLIT_BLOCK_SIZE) {
+    return NULL;
+  }
+
+  char *base = (char *) block;
+  struct mem_block *new_block = (struct mem_block *) (base + total_sz);
+
+  uint remainder_size = old_size - total_sz;
+
+  new_block->size = remainder_size;
+  set_free(new_block);
+
+  new_block->next = block->next;
+  new_block->prev = block;
+
+  if (block->next != NULL) {
+    block->next->prev = new_block;
+  } else {
+    // if block was tail, new_block becomes new tail
+    tail = new_block;
+  }
+
+  block->size = total_sz;
+  set_used(block);
+  block->next = new_block;
+
+  return new_block;
+}
+
+// We have some space like this:
+// +-----------------------------+
+// | mem_block | data            |
+// +-----------------------------+
+// ^           ^
+// |           |
+// |           +--- actual data pointer (for user space programs)
+// |
+// +----- header
+//
+
+// find first free whose size is big enough
+static struct mem_block*
+find_free_first_fit(uint total_sz)
+{
+	struct mem_block *curr = head;
+
+	while (curr != NULL) {
+		if (is_free(curr) && get_size(curr) >= total_sz) {
+			return curr;
+		}
+		curr = curr->next;
+	}
+	return NULL;
+}
+
+// find free block with smallest size  >= total_sz
+static struct mem_block*
+find_free_best_fit(uint total_sz)
+{
+	struct mem_block *curr = head;
+	struct mem_block *best = NULL;
+
+	while (curr != NULL) {
+		if (is_free(curr) && get_size(curr) >= total_sz) {
+			if (best == NULL || get_size(curr) < get_size(best)) {
+				best = curr;
+			}
+		}
+		curr = curr->next;
+	}
+
+	return best;
+}
+
+static struct mem_block*
+find_free_worst_fit(uint total_sz)
+{
+	struct mem_block *curr = head;
+	struct mem_block *worst = NULL;
+
+	while (curr != NULL) {
+		if (is_free(curr) && get_size(curr) >= total_sz) {
+			if (worst == NULL || get_size(curr) > get_size(worst)) {
+				worst = curr;
+			}
+		}
+		curr = curr->next;
+	}
+	return worst;
+}
+
+static struct mem_block *
+find_free_block(uint total_sz)
+{
+	switch (current_fsm) {
+		case FSM_BEST_FIT:
+			return find_free_best_fit(total_sz);
+		case FSM_WORST_FIT:
+			return find_free_worst_fit(total_sz);
+		case FSM_FIRST_FIT:
+		default:
+			return find_free_first_fit(total_sz);
+	}
+}
+
+
+void *
+malloc(uint size)
+{
+  if (size == 0) {
+    return NULL;
+  }
+
+  uint aligned = align16(size);
+  uint total_sz = BLOCK_HEADER_SIZE + aligned;
+
+  //  try to find a suitable free block first
+  struct mem_block *block = find_free_block(total_sz);
+  if (block != NULL) {
+    // take space from this free block
+    split(block, total_sz);
+    set_used(block);
+    return (void *)(block + 1);
+  }
+
+  // no suitable free block, request a new chunk from the OS
+  uint request = total_sz;
+  if (request < PAGE_SIZE) {
+    request = PAGE_SIZE;
+  }
+
+  block = (struct mem_block *) sbrk(request);
+  if ((long)block == -1) {
+    return NULL;
+  }
+
+  // treat the whole new region as a single free block
+  block->size = request;
+  set_free(block);
+  block->next = NULL;
+  block->prev = tail;
+
+  if (head == NULL) {
+    head = block;
+    tail = block;
+  } else {
+    tail->next = block;
+    tail = block;
+  }
+
+  // now carve out the requested block from this new free block
+  struct mem_block *alloc_block = block;
+  split(alloc_block, total_sz);
+  set_used(alloc_block);
+
+  return (void *)(alloc_block + 1);
+}
+// linked list helpers:
+// * add a new block
+// * remove a block
+// * AND make sure you can handle both the (1) block list, and (2) free list
 
 void
-free(void *ap)
-{
-  Header *bp, *p;
-
-  bp = (Header*)ap - 1;
-  for(p = freep; !(bp > p && bp < p->s.ptr); p = p->s.ptr)
-    if(p >= p->s.ptr && (bp > p || bp < p->s.ptr))
-      break;
-  if(bp + bp->s.size == p->s.ptr){
-    bp->s.size += p->s.ptr->s.size;
-    bp->s.ptr = p->s.ptr->s.ptr;
-  } else
-    bp->s.ptr = p->s.ptr;
-  if(p + p->s.size == bp){
-    p->s.size += bp->s.size;
-    p->s.ptr = bp->s.ptr;
-  } else
-    p->s.ptr = bp;
-  freep = p;
-}
-
-static Header*
-morecore(uint nu)
-{
-  char *p;
-  Header *hp;
-
-  if(nu < 4096)
-    nu = 4096;
-  p = sbrk(nu * sizeof(Header));
-  if(p == SBRK_ERROR)
-    return 0;
-  hp = (Header*)p;
-  hp->s.size = nu;
-  free((void*)(hp + 1));
-  return freep;
-}
-
-void*
-malloc(uint nbytes)
-{
-  Header *p, *prevp;
-  uint nunits;
-
-  nunits = (nbytes + sizeof(Header) - 1)/sizeof(Header) + 1;
-  if((prevp = freep) == 0){
-    base.s.ptr = freep = prevp = &base;
-    base.s.size = 0;
+free(void *ptr)
+{
+
+  if (ptr == NULL) {
+  	return;
   }
-  for(p = prevp->s.ptr; ; prevp = p, p = p->s.ptr){
-    if(p->s.size >= nunits){
-      if(p->s.size == nunits)
-        prevp->s.ptr = p->s.ptr;
-      else {
-        p->s.size -= nunits;
-        p += p->s.size;
-        p->s.size = nunits;
-      }
-      freep = prevp;
-      return (void*)(p + 1);
-    }
-    if(p == freep)
-      if((p = morecore(nunits)) == 0)
-        return 0;
+
+  // ptr points to the user data; header is right before that
+  struct mem_block *block = ((struct mem_block *)ptr) -1;
+
+  if (is_free(block)) {
+  	return;
   }
+
+  set_free(block);
+ 
+}
+
+// This is great because we can allocate arrays of things easily
+// And they're zeroed out
+// This function is perfect and never needs to be changed
+void *
+calloc(uint nmemb, uint size)
+{
+  char *mem = malloc(nmemb * size);
+  if (mem == NULL) {
+    return NULL;
+  }
+  memset(mem, 0, nmemb * size);
+  return mem;
+}
+
+// takes a pointer to a previous allocation and resizes it (shrink / grow)
+void *
+realloc(void *ptr, uint size)
+{
+	if (ptr == NULL) {
+		return malloc(size);
+	}
+
+	if (size == 0) {
+		free(ptr);
+		return NULL;
+	}
+
+	struct mem_block *old_block = ((struct mem_block *) ptr) - 1;
+	uint old_total_size = old_block->size;
+	uint old_payload_size = old_total_size - sizeof(struct mem_block);
+
+	void *new_ptr = malloc(size);
+	if (new_ptr == NULL) {
+		return NULL;
+	}
+
+	uint copy_size = old_payload_size < size ? old_payload_size : size;
+	memmove(new_ptr, ptr, copy_size);
+
+	free(ptr);
+
+	return new_ptr;
+}
+
+void
+malloc_print(void)
+{
+	struct mem_block *curr;
+
+	printf("--Current Memory State --\n");
+
+	curr = head;
+	while (curr != NULL) {
+		char *start = (char *)curr;
+		char *end = start + get_size(curr);
+		const char *status = is_free(curr) ? "FREE" : "USED";
+
+		printf("[BLOCK %p-%p] %d\t[%s]\n",
+				start,
+				end,
+				get_size(curr),
+				status);
+				
+		curr = curr->next;
+	}
+
+	printf("\n-- Free List --\n");
+
+	curr = head;
+	int first = 1;
+	while (curr != NULL) {
+		if (is_free(curr)) {
+			if (!first) {
+				printf(" -> ");
+			}
+			printf("[%p]", curr);
+			first = 0;
+		}
+		curr = curr->next;
+	}
+	if (!first) {
+		printf(" -> ");
+	}
+	printf("NULL\n");
+}
+
+void
+malloc_setfsm(int algo)
+{
+  if (algo == FSM_FIRST_FIT ||
+      algo == FSM_BEST_FIT  ||
+      algo == FSM_WORST_FIT) {
+    current_fsm = algo;
+  }
+}
+
+void malloc_name(void *ptr, const char *name) {
+    struct mem_block *block = get_header(ptr);
+    int i;
+    for (i = 0; i < 7 && name[i] != 0; i++) {
+        block->name[i] = name[i];
+    }
+    block->name[i] = 0;
 }
diff --git a/user/user.h b/user/user.h
index 718b656..2a2b379 100644
--- a/user/user.h
+++ b/user/user.h
@@ -12,13 +12,13 @@ int read(int fd, void *buf, int count);
 int close(int fd);
 int kill(int pid);
 int exec(const char* path, char **argv);
-int open(const char* path, int mode);
-int mknod(const char* path, short major, short minor);
-int unlink(const char* path);
+int open(const char*/*str*/ path, int mode);
+int mknod(const char* /*str*/ path, short major, short minor);
+int unlink(const char* /*str*/  path);
 int fstat(int fd, struct stat* st);
-int link(const char* old_path, const char* new_path);
-int mkdir(const char* path);
-int chdir(const char* path);
+int link(const char* /*str*/old_path, const char* /*str*/ new_path);
+int mkdir(const char* /*str*/ path);
+int chdir(const char* /*str*/ path);
 int dup(int fd);
 int getpid(void);
 char* sys_sbrk(int n, int incr);
diff --git a/user/usys.pl b/user/usys.pl
old mode 100755
new mode 100644