Implementing Everything in Go: Built-ins, Pipes, and Jobs

When you write a shell in Go, you quickly realize that the standard library is your best friend. In Dush, we don't just call out to external binaries for everything—we implement as much as possible in pure Go to ensure cross-platform consistency and speed.

Many shells are just thin wrappers around libc. Dush aims to be different. By implementing core utilities as built-ins, we avoid the overhead of process spawning for common tasks.

One of the most visible parts of Dush is the built-in ls. Instead of relying on the system's ls, Dush uses os.ReadDir and a custom renderer. This allows us to:

• Inject icons based on file extensions.
• Provide consistent coloring across Windows, Linux, and macOS.
• Build in human-readable sizes and grid layouts without extra flags.

Implementing pipes (|) in Go is surprisingly elegant. We use io.Pipe() to create a connected reader and writer.

EXPANDCOPY
go
// Conceptual Go implementation
reader, writer := io.Pipe()
cmd1.Stdout = writer
cmd2.Stdin = reader

go func() {
    cmd1.Run()
    writer.Close()
}()
cmd2.Run()

This "pure Go" approach to plumbing ensures that Dush handles data streams efficiently without hitting OS-specific pipe buffer limits too early.

Handling background processes (&) and bringing them back to the foreground (fg) is one of the hardest parts of shell development. Dush uses a centralized JobManager that:

• Wraps os/exec.Cmd.
• Monitors process state via goroutines.
• Handles SIGINT and SIGTSTP forwarding.
• Provides a clean jobs command to see what's running.

Commands like cd, pwd, mkdir, and rm are all implemented using Go's os and path/filepath packages. This means a Dush script written on a Mac will run perfectly on Windows without needing a Mingw or Cygwin environment.

By implementing these features in Go, Dush achieves a level of "portability as a feature." You get the power of a Unix-like environment on any platform Go can compile to.

Dush is a testament to the power of the Go ecosystem for systems programming.

Check out the implementation: https://github.com/fezcode/dush