Minishell

Description

The Minishell project involves creating a simple shell that mimics the functionality of a basic Unix shell. Through this project, you will gain a deep understanding of processes, file descriptors, and various system calls in C.

Project Objectives

• Develop a custom shell that can execute commands, manage file descriptors, and handle process creation.
• Implement features such as redirections, pipes, and environment variable handling.
• Gain hands-on experience with Unix system programming concepts like signals and job control.

Content

• Mandatory Part:

  • Implement a shell with the following features:

    • Display a prompt when waiting for a command.
    • Maintain a working history of commands.
    • Locate and launch executables based on the PATH environment variable or via relative/absolute paths.
    • Handle unquoted and quoted sequences of characters, ensuring proper interpretation of metacharacters.
    • Implement redirections:
      • < for input redirection.
      • > for output redirection.
      • << to read input until a specified delimiter is encountered.
      • >> for output redirection in append mode.
    • Implement pipes (|), connecting the output of one command to the input of the next.
    • Handle environment variables, expanding them to their values.
    • Implement built-in commands such as echo, cd, pwd, export, unset, env, and exit.
    • Manage special keyboard inputs like ctrl-C, ctrl-D, and ctrl-\ in interactive mode.

  • Constraints:

    • Use only one global variable.
    • Ensure that your shell does not interpret unclosed quotes or special characters not required by the subject.

Compilation

To compile the project, ensure that your Makefile includes the following rules: all, clean, fclean and re.

1. Compile the program:

   make

   This will create the minishell executable.

2. Clean object files:

   make clean

3. Remove all generated files, including the executable:

   make fclean

4. Recompile everything from scratch:

   make re

Usage

To use the minishell, run the compiled executable:

./minishell

You can then enter commands at the prompt just like in a regular shell:

$ ls -l
$ echo 'Hello, Minishell!'
$ pwd

You can also use features such as pipes, redirections, and environment variables:

$ echo 'This is a test' > output.txt
$ cat output.txt | grep 'test'

To exit the shell, use the exit command or press ctrl-D.