💻 Minishell

About

This project is about creating a simple shell. Yes, your own little bash. You will learn a lot about processes and file descriptors.

Subject Minishell Project 42

The Minishell program aims to replicate the essential features of a Unix shell, allowing users to enter and execute commands as they would in a typical terminal session.

Features

• Description: Provides an interactive terminal environment where you can execute shell commands.
• Key Features:
  • Supports command execution, input/output redirection, heredoc, pipes, conditional execution, variable expansion, wildcard and quoting.
  • Operates in both interactive and non-interactive modes.
  • Handles interruptions like CTRL-C, CTRL-D or CTRL-\.
  • Implements built-in commands including echo, cd, pwd, export, unset, env, and exit.
• Usage: Run ./minishell and enter commands in the prompt as you would in a standard shell.

Setup

Clone the Repository:

git clone https://github.com/J0hann3/Minishell.git
cd Minishell
make

Usage

Interactive mode

1. Run the program ./minishell without any arguments.
2. Once launched, the program will display a prompt and wait for you to enter commands.
3. Type each command and press ENTER to execute.
4. CTRL-C stops the current command or displays a new prompt.
5. Exit the program by typing exit or pressing CTRL-D.

./minishell
minishell$> echo Hello, world!
Hello, world!
minishell$> ls | grep minishell > output.txt
minishell$> echo s*
src suppr.valgrind
minishell$> export HELLO="hello world"
minishell$> echo "$HELLO"
hello world
minishell$> echo '$HELLO'
$HELLO
minishell$> echo -n "hello " || echo bad && echo world
hello world
minishell$> exit

Non-interactive mode

1. Run a command by piping it to ./minishell.

echo 'ls' | ./minishell
img  includes  Makefile  minishell  obj  README.md  src

New Notion

Built-in commands

• Recreated the following built-in commands:
  • echo with option -n
  • pwd with no options
  • env with no options or arguments
  • cd with only a relative or absolute path
  • export with no options
  • unset with no options
  • exit with no options

Pipes

• Pipes (|) redirect the output of one command to the input of another.
• Handles the use of pipes (|) to chain commands together.
• Minishell supports multiple pipes in the same command line and uses fork processes to execute commands in parallel.

Waitpid

• Waits a process.
• Executed binaries must be waited in the execution flow by the main process.
• At the end of each pipeline, waitpid waits for all processes created within that pipeline.

1. WIFEXITED(status): True if child exited normally.
   • WEXITSTATUS(status): Returns code when child exits.
2. WIFSIGNALED(status): True if child exited because a signal was not caught.
   • WTERMSIG(status): Returns code of the terminating signal.
3. WIFSTOPPED(status): True if child is stopped.
   • WSTOPSIG(status): Returns code of the stop signal.

Exit Status

• Returns a command's exit status that is provided by the waitpid, or 128 + n if terminated by signal n.
• The exit status of a pipeline is the exit status of the last command.
• For commands using && and ||, the exit status is that of the last command executed.

Readline

• Function that reads from the standard input.
• Keeps a history of the command entered in the program.
• Supports navigating through command history using the arrow keys.

Binary trees

• Uses binary trees to structure command execution and establish command priorities.
• Implements priorities with parentheses (no sub-shells implemented).

Redirection and Heredoc

• Use dup and dup2 to manage input/output redirection.
• Create processes to handle multi-heredoc.
• Redirection are processed in the order they appear, from left to right.

./minishell
minishell$> ls | grep src > outfile > outfile1
minishell$> ls | grep src >> outfile >> outfile1
minishell$> < infile grep obj | grep src > outfile
minishell$> cat <<hello <<world
> bad
> hello
> good
> world
good

Code Structure

The main function operates as follows:

init env
while (!exit)
	readline
	if (heredoc)
		read heredoc
	history
	parse
	get PATH
	exec command