shell-c

A POSIX-compliant Unix shell implemented in C.

Features

• Pipelines — arbitrary-length pipelines (cmd1 | cmd2 | cmd3)
• I/O redirection — <, >, >>
• Background execution — trailing &
• Signal handling — Ctrl+C and Ctrl+Z reach the foreground pipeline, not the shell; background children are reaped asynchronously via SIGCHLD
• Process groups — each pipeline runs in its own process group so signals reach every stage
• Built-ins — cd, exit, export, history
• Command history — ring buffer of the last 100 commands
• Trace mode — --trace logs every fork, exec, and pipe to stderr

Build

make

Requires a C11 compiler and POSIX.1-2008.

Usage

./shell-c           # interactive mode
./shell-c --trace   # with execution tracing

Built-in commands

Command	Description
cd [dir]	Change directory; defaults to $HOME
exit [code]	Exit with optional status code
export VAR=VALUE	Set an environment variable
history	Print command history