~# Minishell

Custom implementation of a terminal (a small Unix shell) with emphasis on parsing and execution.

This repository contains a compact shell written in C that implements command parsing, execution, pipes, I/O redirections, environment handling and common builtin commands. It is intended as a learning / educational project and a lightweight shell replacement for simple command-line tasks.

Table of Contents

• Features
• Requirements
• Build
• Usage
• Examples
• Supported Builtins
• Behavior & Design Notes

Features

• Tokenization and parsing of command lines with:
  • single and double quotes
  • environment variable expansion ($VAR)
  • handling of whitespace
• Execution of:
  • external binaries (via execve)
  • pipeline chains (using pipes)
  • I/O redirections: >, >>, <
  • here-document (<<) support (if implemented)
• Basic job of a shell environment:
  • maintains a process environment
  • builtin commands for shell management
• Signal handling for interactive mode (e.g., Ctrl-C behavior)

The implementation focuses on parsing correctness and the execution flow (fork/exec, file descriptor management).

Requirements

• POSIX-compatible system (Linux or macOS)
• GCC or clang (C compiler)
• make (Makefile provided)

Build

Clone the repository and run make:

git clone https://github.com/oishchen42/Minishell.git
cd Minishell
make

This will produce an executable (commonly named minishell — check the Makefile for the exact target).

To clean build artifacts:

make clean

Usage

Start the shell:

./minishell

You will see a prompt (depending on implementation). Type commands as you would in a normal shell:

• Run programs: ls -la
• Use pipes: cat file.txt | grep foo | wc -l
• Redirect output: echo hello > out.txt
• Append output: echo world >> out.txt
• Redirect input: wc -l < file.txt
• Combine pipes and redirects: grep pattern file | sort > result.txt

Exit the shell with the exit builtin or Ctrl-D (EOF) if supported.

Examples

• Run a single command:

  /bin/ls -la
  

• Pipelines:

  ps aux | grep minishell | awk '{print $2}'
  

• Redirections:

  echo "hello" > hello.txt
  cat < hello.txt
  

• Variable expansion:

  echo $HOME
  

• Quoted strings:

  echo "a string with spaces"
  echo 'literal $HOME is not expanded in single quotes'
  

Supported Builtins

Common builtin commands implemented in this project typically include:

• cd — change current directory
• echo — print text
• pwd — print working directory
• export — set environment variables
• unset — unset environment variables
• env — print environment
• exit — exit the shell

Check the source for the exact set and behavior of builtins.

Behavior & Design Notes

• Parsing: tokens are split respecting quotes and expansions; the parser builds an execution plan (commands, args, redirections, and pipe relationships).
• Execution: the shell forks child processes and uses execve to run external commands. File descriptors for redirections and pipes are set up before exec.
• Signals: the shell should handle interactive signals (SIGINT, SIGQUIT) appropriately — e.g., allow interrupting running child processes without exiting the shell itself.
• Exit codes: the shell should propagate the exit status of the last foreground command.