goshell - Unix Shell written in Go

A custom Unix shell built from scratch in Go to study Linux internals: processes, syscalls, file descriptors, pipes, and signals.

Features

Implemented

• REPL - interactive read-eval-print loop
• External commands - runs any program via fork + execve + wait (os/exec)
• Builtins - cd, pwd, exit, export, unset, env
• Environment variables - export VAR=value, $VAR expansion in arguments
• I/O redirection - >, >>, <, 2>
• Pipes - cmd1 | cmd2 | cmd3 (arbitrary length pipelines)

Planned

• Signal handling (Ctrl+C, Ctrl+Z)
• Job control (&, fg, bg, jobs)
• Globbing (*, ?, ~)
• Command substitution $(cmd)
• Process inspector (/proc reader)

Project structure

main.go       - REPL loop, entry point
parser.go     - tokenizer, $VAR expansion, redirect/pipe parsing
executor.go   - process execution, pipes, I/O redirection
builtins.go   - built-in commands (cd, pwd, exit, export, unset, env)

Build & Run

go run .

Linux internals covered

Stage	Topic	Key syscalls
1. REPL & processes	Process lifecycle	fork, execve, wait4
2. Environment	Environment passing	execve(path, argv, envp)
3. Redirects	File descriptors	open, close, dup2
4. Pipes	IPC, kernel buffers	pipe, dup2, close
5. Signals	Signal delivery	sigaction, kill
6. Job control	Process groups, sessions	setpgid, tcsetpgrp