This project was developed as part of the 42 Coding School curriculum by cvizcain and gisidro-

Minishell

Description

Minishell is a simple UNIX shell implemented in C as part of the 42 School curriculum. The goal of the project is to recreate the core functionality of a POSIX-compliant shell — similar to Bash — from scratch.

The shell supports interactive command input with history, execution of external binaries via PATH resolution or explicit paths, a full set of built-in commands, I/O redirections, pipes, environment variable expansion, and correct signal handling. The bonus part extends the shell with logical operators (&&, ||), sub-shell grouping with parentheses, and wildcard (*) expansion in the current directory.

Key features

• Prompt & history – displays a prompt and keeps a command history (navigable with arrow keys)
• Command execution – resolves executables using PATH, relative paths, or absolute paths
• Built-in commands – echo, cd, pwd, export, unset, env, exit
• Redirections – < (input), > (output), >> (append), << (here-doc)
• Pipes – chains commands with |
• Variable expansion – $VAR and $? (exit status of last command)
• Quoting – single quotes preserve literals; double quotes preserve literals except $
• Signals – Ctrl-C (new prompt), Ctrl-D (exit), Ctrl-\ (ignored in interactive mode)
• Bonus – && / || operators, () grouping, * glob expansion

Instructions

Requirements

Linux (Debian/Ubuntu):

• cc compiler
• GNU make
• readline development library:

sudo apt-get install libreadline-dev

Compilation

Build the mandatory part:

make

Build with bonus features (&&, ||, (), *):

make bonus

Running

./minishell

The shell starts in interactive mode. Type commands just like in Bash.

Usage examples

# Basic command
$ echo "Hello, World!"
Hello, World!

# Pipe
$ ls -la | grep ".c"

# Redirections
$ echo "log entry" >> log.txt
$ cat < log.txt

# Here-doc
$ cat << EOF
> line one
> EOF

# Variable expansion
$ export MY_VAR=42
$ echo $MY_VAR
42
$ echo $?
0

# Bonus – logical operators and grouping
$ (echo "a" && echo "b") || echo "c"
a
b

# Bonus – wildcard expansion
$ ls *.c

Built-in commands

Command	Description
echo [-n] [string]	Print text to stdout; -n suppresses the trailing newline
cd [path]	Change the current working directory
pwd	Print the current working directory
export [KEY=VALUE]	Set or display environment variables
unset KEY	Remove an environment variable
env	Print all environment variables
exit [n]	Exit the shell with optional exit code

Resources

References

• Bash Reference Manual – authoritative guide to Bash behaviour used as the reference implementation
• GNU readline library – documentation for the readline API used for line editing and history
• man 2 execve – Linux manual page for execve
• man 2 fork – Linux manual page for fork
• man 2 pipe – Linux manual page for pipe
• man 7 signal – Linux manual page for signals
• Writing a Unix Shell – Part I – tutorial series on building a shell step by step
• The Architecture of Open Source Applications – The Bash Shell – high-level design overview of Bash internals

AI Usage

AI tools were used in this project for the following purposes:

• Testing – to help create and run test cases that verify correct shell behaviour
• Documentation – for drafting parts of the inline code documentation
• Understanding – to help understand specific aspects of the codebase and underlying system concepts

All AI-assisted content was reviewed, tested, and validated manually by the project authors.