This project has been created as part of the 42 curriculum by aykrifa, cbordeau.

Minishell

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Description

Minishell is a minimal Unix shell written in C, built as part of the 42 school curriculum. The goal is to reproduce the core behavior of Bash — from command parsing and execution to redirections, pipes, signals, and built-in commands.

The shell is built around an Abstract Syntax Tree (AST) — each command line is parsed into a tree of nodes (EXEC, PIPE, REDIR, LINE) that is then walked recursively at execution time. This architecture is directly inspired by the shell from the xv6 RISC-V teaching kernel by MIT, extended with full Bash quoting rules, environment variable expansion, here-doc, wildcards, and logical operators.

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Features

Core

• Interactive prompt with command history (via GNU Readline)
• Command lookup via PATH, relative path, or absolute path
• Single global variable for signal number only (Norm-compliant)

Quoting

• 'single quotes' — no interpretation of any metacharacter
• "double quotes" — metacharacters suppressed except $

Redirections

Operator	Behavior
<	Redirect stdin from file
>	Redirect stdout to file (truncate)
>>	Redirect stdout to file (append)
<<	Here-doc — read stdin until delimiter

Pipes & Logical Operators (bonus)

Operator	Behavior
|	Pipe — connects stdout of left to stdin of right
&&	Execute right only if left succeeds
||	Execute right only if left fails
( )	Group commands, control evaluation priority

Expansion

• $VAR — expand environment variable
• $? — expand exit status of last foreground pipeline
• * — wildcard glob for current working directory (bonus)

Signals

Signal	Interactive behavior
Ctrl-C	Display new prompt on a new line
Ctrl-D	Exit the shell
Ctrl-\	Does nothing

Built-in Commands

Command	Description
echo [-n]	Print arguments to stdout, -n suppresses trailing newline
cd <path>	Change working directory (relative or absolute)
pwd	Print current working directory
export [VAR=val]	Set or display environment variables
unset <VAR>	Remove an environment variable
env	Print all environment variables
exit [n]	Exit the shell with optional status code

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Instructions

Requirements

• cc (GCC or Clang)
• GNU Readline library (libreadline-dev on Debian/Ubuntu)
• make

Compilation

make

This compiles libft then the shell. The binary is minishell.

Running

./minishell

Makefile rules

Rule	Effect
make / make all	Build the project
make clean	Remove object files
make fclean	Remove object files and binary
make re	fclean + all
make bonus	Build with bonus features

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Resources

References

• xv6 RISC-V shell — MIT 6.1810 teaching OS. The AST-based parser and recursive tree executor in this project are directly inspired by user/sh.c from the xv6-riscv source: https://github.com/mit-pdos/xv6-riscv
• GNU Bash Reference Manual — https://www.gnu.org/software/bash/manual/bash.html
• Advanced Programming in the UNIX Environment — W. Richard Stevens & Stephen A. Rago
• GNU Readline Library — https://tiswww.case.edu/php/chet/readline/rltop.html
• POSIX.1-2017 Shell & Utilities — https://pubs.opengroup.org/onlinepubs/9699919799/