Simple: S3 Downloader

Interactive console app for downloading objects from an AWS S3 bucket to a local folder.

Tech specs

• .NET: .NET 10
• AWS SDK: AWSSDK.S3
• Console UI: Terminal.Gui
• Logging: Microsoft.Extensions.Logging.Console
• Testing: xUnit v3 (xunit.v3.mtp-v2) on Microsoft Testing Platform
• Package management: Central Package Management (Directory.Packages.props)

How it generally works

1. The console app prompts you for:
   • bucket name
   • optional prefix filter
   • local download directory
   • optional region
   • overwrite behavior
   • max concurrency
2. S3DownloaderService:
   • lists objects via ListObjectsV2
   • skips “directory marker” keys (keys ending in /)
   • downloads each object via GetObjectAsync
   • streams the response stream to a local file path
   • limits parallel downloads using a semaphore (MaxConcurrency)
   • reports per-object progress via callback so the console UI can render progress bars

Configuration and AWS profile selection

The console app creates the S3 client using this precedence order:

1. Default AWS SDK behavior (no explicit profile)
2. appsettings.json value AWS:Profile
3. CLI argument --profile <name> / --profile=<name>

If a profile name is specified (via config or CLI), credentials are resolved from the standard AWS shared config/credentials files (e.g. %UserProfile%\\.aws\\config on Windows).

appsettings.json

File: src/SimpleAWS.S3.Downloader.Console/appsettings.json

{
  "AWS": {
    "Profile": null,
    "Region": null
  },
  "App": {
    "DefaultDownloadPath": null
  },
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft": "Warning",
      "System": "Warning"
    }
  }
}

Available settings:

• AWS:Profile: Named AWS profile to use from the shared config/credentials files. When null, the SDK default chain is used.
• AWS:Region: AWS region override. When null, the region is taken from the selected profile.
• App:DefaultDownloadPath: Default local download folder shown in the UI. When null, the current working directory is used.
• Logging:LogLevel:Default, Logging:LogLevel:Microsoft, Logging:LogLevel:System: Standard Microsoft.Extensions.Logging filter settings.

Command line arguments

The app is primarily interactive. Supported args:

• --profile <name> or --profile=<name>
  • Overrides AWS:Profile from appsettings.json.
  • Forces the app to use the named shared-config profile.

When using dotnet run, pass args after --:

dotnet run --project src\\SimpleAWS.S3.Downloader.Console -- --profile master

Run the console app

dotnet run --project src\\SimpleAWS.S3.Downloader.Console

Run tests

This repo uses xUnit v3 + Microsoft Testing Platform on .NET 10.

Run the test project (instead of dotnet test):

dotnet run --project src\\SimpleAWS.S3.Downloader.Core.Tests\\SimpleAWS.S3.Downloader.Core.Tests.csproj -c Release