bnto-shell

Shell command execution for native targets. Runs external CLI tools via ProcessContext::run_command().

Overview

bnto-shell provides the shell-command processor — a generic NodeProcessor that executes external CLI tools. This enables connector-as-recipe architecture: recipes can wrap any CLI tool (ffmpeg, yt-dlp, imagemagick) without needing a dedicated Rust processor for each one.

Native-only: registered behind #[cfg(feature = "native")] in bnto-engine. Browser (WASM) gets NoopContext which blocks execution.

Processors

Output Modes

• stdout (default): captures command stdout as a single output file
• file: runs command in a temp dir, collects written files as output. Use {{output_dir}} in args to inject the temp directory path. Designed for tools like yt-dlp and ffmpeg that write to disk. Output files use FileData::Path (zero-copy, not read into memory).

Security

All commands pass through validate.rs before execution:

• Shell denylist: bash, sh, zsh, powershell, and other shell interpreters are rejected. Commands must be bare binary names (e.g., ffmpeg, not bash -c "ffmpeg ...").
• Path validation: absolute paths, relative paths, and parent traversal are rejected. Commands are resolved via PATH by the OS.
• Environment sanitization: LD_PRELOAD, DYLD_*, PATH, HOME, SHELL, TMPDIR are silently stripped from recipe-provided env vars.

Conditional Args

The args array supports conditional flag groups via nested arrays:

"args": ["--always", ["--cookies-from-browser", "{{fields.browser}}"], "{{fields.thumbnail}}"]

After template resolution, empty strings drop silently, and nested arrays where any element is empty drop the entire group. This enables optional flags without recipe-level if/else.

Directory Structure

src/
├── lib.rs           # Public exports
├── execute.rs       # ShellCommand processor (param parsing, mode dispatch)
├── args.rs          # Conditional arg groups + {{url}}/{{input}} placeholders
├── stdout_mode.rs   # "stdout" output mode
├── file_mode.rs     # "file" output mode ({{output_dir}} temp dir)
├── output_files.rs  # Collects written files as path references
├── parameters.rs    # Node parameter schema
└── validate.rs      # Security validation (command denylist, env sanitization)

Development

cargo test -p bnto-shell    # Native unit tests (security + processor)