Unix-Shell

A Unix-like shell built from scratch in C++ with pipelines, job control, I/O redirection, persistent history, and tab completion.

• Command execution — runs external commands via fork() + execvp()
• Pipelines — two-command pipes using pipe(), fork(), and dup2()
• Background jobs — run commands with &, track with a jobs builtin
• Job control — job number recycling, async reaping via waitpid(WNOHANG)
• I/O redirection — >, <, >> support
• Shell history — persistent history with HISTFILE, history, history -r, history -w, history -a
• Tab completion — custom TAB completion using complete -C external completer scripts with longest-common-prefix logic and bell-on-first / list-on-second behavior
• Variable expansion — declare builtin and expandVars() for parameter expansion
• GNU Readline — full readline integration for line editing

Requirements: Linux, g++, GNU Readline

# Clone the repo
git clone https://github.com/vinaayy06/shell.git
cd shell
# Install readline (if not already installed)
sudo apt-get install libreadline-dev
# Build
g++ -std=c++17 src/*.cpp -lreadline -o shell
# Run
./shell

# Basic command
$ ls -la
# Pipeline
$ ls | grep .cpp
# Background job
$ sleep 10 &
[1] 12345
# Check jobs
$ jobs
[1]+ Running sleep 10
# Redirect output
$ echo hello > out.txt
# Variable declaration
$ declare x=42
$ echo $x
42
# History
$ history
$ history -w # write to HISTFILE
$ history -r # read from HISTFILE

• Process management: fork(), exec(), waitpid()
• IPC: pipe(), dup2() for pipeline chaining
• Signal handling: background job reaping with WNOHANG
• Readline integration via GNU Readline library
• Tab completion via external completer scripts (complete -C)

C++ 100%