Minishell

lucinguy & ccauderl
(piscine of september's 2025 - 42 PARIS)

Description

The Minishell project is about writing our own shell, based on bash posix. We manage just some essential features, but a lot of special characters are not processed (like ; or &&). This project is part of the 42 curriculum. The libft library we use is the first project of the 42 curriculum. We have chosen Oswen's for practicality.

Instructions

Our minishel contains the following features, it can :

• Display of a prompt when waiting for a new command
• Have a working history
• Search and launch the right executable (based on the PATH or using a relative/absolute path)
• Indicate a received signal.
• Handle single and double quotes
• Handle the following redirections:
  • < to redirect input
  • > to redirect output
  • << and >>
• pipes
• Handle environment variables
• Handle ctrl-C, ctrl-D and ctrl-\
• The following built-in :
  • echo (and its flag -n)
  • cd with only a relative or absolute path
  • pwd
  • export
  • unset
  • env (with no argument)
  • exit

Parts

We divided the project into several sections :

• Signal : handle the received signals and execute the right behaviour
• Environment : manage the environment variables and recreate some if none are accessible
• Tokenizer : expand environment variables, divide the received prompt into tokens, assign to each token a type (ex: WORD, PIPE, REDIRECTION, ...)
• Execution : Execute the commands and the redirections
• Built-in : the built-in functions, which are accessible even if there is no environment variable.

Instructions

Usage

1. make all
2. ./minishell (no args)
3. execute commands in our minishell

Examples
in minishell :

> ls -la | grep "." | wc
> < Makefile wc | cat > out
> << EOF cat
> echo "hi $USER, you're currently here : $PWD"
> export NEWVAR=blabla (then again export to see the result)
> unset NEWVAR
> cd srcs/
> echo -n hello >> out
> echo $?
> env
> pwd

Check leaks
valgrind --suppressions=readline.supp --leak-check=full --show-leak-kinds=all ./minishell

Resources

Bash Reference Manual : https://www.gnu.org/software/bash/manual/bash.html#What-is-Bash_003f

A tutorial to start the tokenizer : https://mvsrgc.xyz/posts/Write-a-Shell-Tokenizer-in-C/

GNU Readline Library : https://tiswww.cwru.edu/php/chet/readline/readline.html

A tutorial about signals : https://www.geeksforgeeks.org/c/signals-c-language/

Another tutorial about enumerations: https://www.w3schools.com/c/c_enums.php

A project subject about writing a shell from the Northeatern University: https://course.ccs.neu.edu/cs3650sp23/p1.html

A site used to have the manual to the authorized functions: https://man7.org/linux/man-pages/