minishell

A tiny Unix shell written in C, inspired by bash and built as part of the 42 cursus.
The goal: travel back in time and talk to your computer through a simple, interactive command line.

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Features

• Prompt that waits for a new command
• Command history (powered by readline)
• PATH resolution for executables, plus support for:
  • Absolute paths (/bin/ls)
  • Relative paths (./my_script.sh)
• Single global variable used only for signal handling
• Proper handling of quotes:
  • Single quotes '...' keep everything literal
  • Double quotes "..." expand $VAR but keep other meta-characters
• Redirections:
  • < — redirect input
  • > — redirect output (truncate)
  • >> — redirect output (append)
  • << — heredoc until a given delimiter (no history update)
• Pipes: cmd1 | cmd2 | cmd3
• Environment variables:
  • $VAR expansion
  • $? for the last exit status
• Logical operators and precedence:
  • && and ||
  • Parentheses for priority: (cmd1 && cmd2) || cmd3
• Signal handling (interactive mode):
  • Ctrl-C prints a new prompt on a new line
  • Ctrl-D exits the shell
  • Ctrl-\ is ignored, like in bash
• No unrequired special characters: no interpretation of unclosed quotes, \, ;, etc.

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Built-in commands

Implemented built-ins (without extra options/flags unless specified):

• echo [-n] – print text with optional no-newline
• cd [path] – change directory (relative or absolute)
• pwd – print current working directory
• export – print environment (and manage exported variables internally)
• unset – remove environment variables
• env – print current environment
• exit – exit minishell

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Tech & Constraints

• Language: C
• Build system: Makefile
  • Targets: all, clean, fclean, re
• Allowed external functions (as per subject):
  • readline, add_history, rl_clear_history, rl_on_new_line, rl_replace_line, rl_redisplay
  • printf, malloc, free, write
  • access, open, read, close
  • fork, wait, waitpid, wait3, wait4
  • signal, sigaction, sigemptyset, sigaddset, kill
  • exit
  • getcwd, chdir
  • stat, lstat, fstat, unlink
  • execve, dup, dup2, pipe
  • opendir, readdir, closedir
  • strerror, perror
  • isatty, ttyname, ttyslot, ioctl
  • getenv
  • tcsetattr, tcgetattr
  • tgetent, tgetflag, tgetnum, tgetstr, tgoto, tputs
• Libft: allowed and used
• Memory: no leaks allowed in my code (the known readline leaks are tolerated by the subject)

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Getting Started

Prerequisites

• gcc or clang
• make
• readline development headers installed
  (e.g. on macOS: brew install readline, on Linux: sudo apt install libreadline-dev)

Build

bash make This will compile the project and create the minishell executable.

To clean object files: make clean To clean everything (including the executable): make fclean To rebuild from scratch: make re

Usage

Launch: ./minishell You’ll see a prompt like: minishell$

Basic examples:

Simple command

minishell$ ls -la

With pipes

minishell$ ls | grep .c | wc -l

Redirections

minishell$ cat < input.txt minishell$ echo "hello" > out.txt minishell$ echo "another line" >> out.txt

Heredoc

minishell$ cat << EOF type anything here until this line: EOF

Environment

minishell$ echo $HOME minishell$ echo $?

Logical operators

minishell$ mkdir test && cd test minishell$ false || echo "this runs" minishell$ (false && echo nope) || echo "this runs instead"

Exit options: Ctrl-D on an empty line exit