This project has been developed as part of the 42 curriculum by atabarea and medel-ca.

Minishell

Minishell is a minimal command-line shell written in C. It supports basic functionalities like command execution, pipes, redirections, and environment variable handling, similar to a simplified version of Bash.

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Table of Contents

1. Description
2. Instructions
3. Resources

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Description

Minishell is designed to demonstrate low-level system programming concepts in C, including:

• Executing system commands.
• Input/output redirections (>, >>, <).
• Command pipelines (|).
• Expanding environment variables ($HOME, $PATH, etc.).
• Basic built-in commands: cd, echo, exit, export, unset.
• Syntax error handling.

It serves as a learning exercise for processes, pipes, memory management, and command parsing in C.

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Instructions

1. Clone the repository

2. Go into the minishell folder

cd minishell

3. Compile the program using Make

make

4. Run the program:

./minishell

5. A prompt will appear. You may enter your commands to be executed. Our minishell supports:

• Prompt display
• Command history (up and down arrows)
• System executables available from the environment (ls, cat, grep, etc)
• Local executables (./minishell)
• Builtin commands:
  • echo (and option -n)
  • cd (with only a relative or absolute path)
  • pwd (no options)
  • export (no options)
  • unset (no options)
  • env (no options or arguments)
  • exit (with exit number but no other options)
• Pipes | which redirect output from one command to input for the next
• Redirections:
  • '>' redirects output
  • '>>' redirects output in append mode
  • < redirects input
  • << DELIMITER displays a new prompt, reads user input until reaching DELIMITER, redirects user input to command input (does not update history)
• Environment variables (i.e. $USER or $VAR) that expand to their values.
• $? expands to the exit status of the most recently executed foreground pipeline.
• $$ expands to the process ID.
• User keyboard signals:
  • ctrl-c: When used in the father process displays a new prompt line. When used during the execution of a command ends the command (try with sleep 10)
  • ctrl-d When used in the father process exits the shell. When used during the execution of a command is ignored (try with sleep 10)
  • ctrl-\ does nothing However, Minishell does not support , ;, &&, ||, or wildcards.

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Resources

First aproximations to the project: Minishell: Building a mini-bash MINISHELL 42: parsing Minishell explained The bash guide

Lexer and Parser of the input: Arbol de sintaxis abstracta Context free grammar Shell command lexer Lexical analyzer in C

Executing child processes and redirections: Pipe() system call

Other useful links: Explain shell