Minishell

Created by: Sheree Morphett, Jenny Boucher

The Minishell project is a part of the 42-cursus group project, where we successfully built a simple shell program in C. The shell acts as a command-line interpreter, allowing users to execute commands, handle environment variables, perform input/output redirection, and manage pipelines. It also supports built-in commands like echo, cd, pwd, export, unset, env, and exit.

Project Overview

The Minishell project aims to create a basic shell similar to the popular Unix shell, bash. It provides a command prompt, reads user input, and executes commands with the correct output. The shell handles various scenarios, including input/output redirection, pipeline execution, and environment variable expansion.

Features Implemented

• Command Execution: The Minishell is capable of searching and launching the appropriate executable file based on the PATH variable. Users can execute commands by providing an absolute or relative path.

• Input/Output Redirection: The shell supports redirection of input and output using the <, >, >> symbols. It allows users to redirect the standard input and output of commands to or from files.

• Here-Documents: The << symbol allows users to specify a delimiter and read input until a line containing the delimiter is encountered. However, this input is not added to the command history.

• Pipelines: The Minishell implements pipes (|) to create a sequence of commands where the output of one command is connected to the input of the next command.

• Environment Variable Expansion: Users can use $ followed by a sequence of characters to expand environment variables to their values.

• Built-in Commands: The shell supports various built-in commands, including:

  • echo: Displays text with an option to omit the trailing newline (-n).
  • cd: Changes the current directory to a specified relative or absolute path.
  • pwd: Displays the current working directory.
  • export: Sets environment variables.
  • unset: Unsets environment variables.
  • env: Displays the environment variables.
  • exit: Exits the shell.

• Signal Handling: The shell properly handles signals like SIGINT (Ctrl+C), SIGQUIT (Ctrl+), and SIGTERM.

Project Execution

When the Minishell is executed, it displays a prompt (e.g., $ or minishell$) and waits for the user to input a command. Upon receiving a command, it parses the input, identifies built-in commands, and executes them if applicable. If the command is not built-in, it searches for the corresponding executable in the system's PATH or specified absolute/relative path and executes it.

The shell maintains a history of executed commands, allowing users to access previously entered commands using the arrow keys.

Conclusion

The Minishell project provides a practical learning experience in C programming, file I/O, process management, signal handling, and string manipulation. It allows us to gain a better understanding of how shells work and how they execute commands in a Unix-like environment. By completing this project, we strengthen our programming skills and improve our ability to collaborate effectively in a team.