minishell

A small Unix shell written in C, built as part of the 42 curriculum. It reads command lines with a prompt, parses them into a command tree, and executes them the way bash does — with pipes, redirections, quoting, environment-variable expansion, wildcards, signals, and a set of built-in commands. A bonus version adds logical operators (&&, ||) and parentheses for grouping.

Features

Command line

• Interactive prompt with line editing and command history (via readline)
• Runs executables by absolute path, relative path, or by searching $PATH
• Proper exit statuses, including $?

Quoting & expansion

• Single quotes '…' — everything literal
• Double quotes "…" — literal except variable expansion
• Environment variable expansion: $VAR, $? (last exit status)
• Wildcard expansion: * in the current directory

Redirections & pipes

• Input <, output >, append >>
• Heredoc << (with expansion of the delimiter body)
• Pipelines cmd1 | cmd2 | cmd3

Signals

• Ctrl-C — new prompt on a fresh line
• Ctrl-D — exits the shell (EOF)
• Ctrl-\ — ignored, like in bash

Built-in commands

Builtin	Description
echo	print arguments, supports -n
cd	change directory
pwd	print working directory
export	set / list environment variables
unset	remove environment variables
env	print the environment
exit	quit the shell

Bonus

• Logical operators && and ||
• Parentheses ( … ) for grouping and precedence
• Wildcards

Build

Requires cc, make, and the readline library.

make          # builds ./minishell (mandatory)
make bonus    # builds ./minishell_bonus (&&, ||, parentheses)
make clean    # remove object files
make fclean   # remove objects and binaries
make re       # full rebuild

On macOS, readline is expected under a Homebrew prefix; adjust the readline -L/-I paths in the Makefile to match your install if needed.

Usage

./minishell

minishell$ echo "hello $USER" | tr a-z A-Z
HELLO MOEL-AMR
minishell$ ls -la > out.txt && cat out.txt
minishell$ cat << EOF
> line one
> EOF
line one
minishell$ export NAME=42 && echo $NAME
42
minishell$ exit

Project structure

minishell/
├── Makefile
├── includes/            # headers (mandatory)
├── includes_bonus/      # headers (bonus)
├── main_m/              # entry point & main loop
├── parsing/             # lexer, quotes, syntax checks, command tree
├── execution/           # exec tree, pipes, redirections, heredoc, signals
├── exec_continue/       # variable / argument expansion, wildcards
├── built_ins/           # echo, cd, pwd, export, unset, env, exit
├── str_utils/           # small string / libft-style helpers
└── *_bonus/             # bonus counterparts of the above

How it works

1. Read — readline prints the prompt and returns the line; non-empty lines are added to history.
2. Lex & parse — the line is tokenized (words, quotes, operators, redirections) and syntax-checked, then built into a tree of commands.
3. Expand — environment variables, $?, and wildcards are expanded on the arguments; quoting rules decide what gets expanded.
4. Execute — the tree is walked: pipes are wired with pipe()/dup2(), redirections are opened, heredocs are collected, built-ins run in-process, and external commands are fork/execve'd. The final exit status becomes $?.

Authors

• ELamraniG — github.com/ELamraniG
• Jihad Hamdaoui (Bladesjj) — github.com/Bladesjj

Built for the 42 minishell project.