C - Simple Shell

📚 Description

This project consists of creating a simple UNIX command interpreter, similar to /bin/sh, capable of executing commands both in interactive and non-interactive modes.

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🛠 Architecture Overview

Here is a flowchart illustrating the internal workflow of the Simple Shell:

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📑 Table of Contents

• Learning Objectives
• Requirements
• Allowed Functions and System Calls
• Usage
  • Interactive Mode
  • Non-Interactive Mode
  • Example with cat
• Installation
• Project Files
  • 1. _memcpy.c
  • 2. _strcpy.c
  • 3. _strdup.c
  • 4. _strncmp.c
  • 5. builtin.c
  • 6. executor.c
  • 7. find.c
  • 8. input.c
  • 9. main.c
  • 10. main.h
  • 11. parser.c
• Testing
• GitHub
• Authors
• License

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🎯Learning Objectives

• Understand the history of Unix and its key contributors.
• Know who designed the original Unix operating system and the UNIX shell.
• Discover the B programming language and its creator.
• Understand who Ken Thompson is.
• Learn how a shell works internally.
• Understand process concepts: pid and ppid.
• Manage environment variables within a process.
• Distinguish between functions and system calls.
• Create new processes (fork) and execute programs (execve).
• Use the PATH environment variable to locate executable programs.
• Wait for process termination (wait).
• Handle "end-of-file" (EOF) conditions.

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📋Requirements

• Allowed editors: vi, vim, emacs
• Compilation on Ubuntu 20.04 LTS with:

  gcc -Wall -Werror -Wextra -pedantic -std=gnu89

• A README.md file must be present at the root of the project.
• Code must follow the Betty coding style.
• No memory leaks are allowed.
• Maximum 5 functions per file.
• Header files must be include guarded.
• Use system calls only when necessary.

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🛠Allowed Functions and System Calls

You are allowed to use the following C standard functions and system calls:

• Standard C library functions from string.h
• access, chdir, close, closedir, execve, exit, _exit
• fflush, fork, free, getcwd, getline, getpid, isatty, kill
• malloc, open, opendir, perror
• printf, fprintf, vfprintf, sprintf, putchar
• read, readdir, signal
• stat, lstat, fstat
• strtok, wait, waitpid, wait3, wait4
• write

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⚙Usage

Interactive Mode

$ ./hsh
($) /bin/ls
file1 file2 shell.c
($) exit
$

Non-Interactive Mode

Execute commands from input without an interactive prompt.

$ echo "/bin/ls" | ./hsh
file1 file2 shell.c

Example with cat

Running multiple commands through a file:

$ cat commands.txt | ./hsh
file1 file2 shell.c
file1 file2 shell.c

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📥Installation

1. Clone the repository

Clone the repository by running the following command:

git clone https://github.com/Roullito/holbertonschool-simple_shell.git
cd your-repo-name

Replace YourUsername/your-repo-name with the actual path to this repository.

2. Install the man page

We provide a script to automatically install the custom man page for our Simple Shell.

Run the following command:

./install_manpage.sh

This will:

• Copy shell.1 to your local man directory (/usr/local/share/man/man1/).
• Update the man database.
• Allow you to type man shell from anywhere to access the manual.

Note:
You might need sudo permissions to install the man page, depending on your system configuration.

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🗂Project Files

1. _memcpy.c

• Description: Implements the _memcpy function that copies a memory area from one location to another.
• Purpose: Used for copying a block of memory from the source to the destination.

2. _strcpy.c

• Description: Implements the _strcpy function that copies the string pointed to by src to the buffer pointed by dest.
• Purpose: Essential for copying strings within the shell's operations.

3. _strdup.c

• Description: Implements the _strdup function that creates a duplicate of a string by allocating new memory.
• Purpose: Useful when we need to duplicate strings, particularly for handling environment variables or command arguments.

4. _strncmp.c

• Description: Implements the _strncmp function that compares up to n characters of two strings.
• Purpose: A custom comparison function to avoid using the standard strncmp for matching strings, often used for commands in the shell.

5. builtin.c

• Description: Implements the handle_builtin function that manages built-in shell commands like exit.
• Purpose: Allows the shell to execute internal commands directly without needing to invoke an external process.

6. executor.c

• Description: Implements the execute function, which creates a child process to execute commands.
• Purpose: Handles the creation of processes for running commands within the shell.

7. find.c

• Description: Implements the _which function that finds the full path of a command using the PATH environment variable.
• Purpose: Determines the location of executable files, helping the shell find and execute commands.

8. input.c

• Description: Implements the _getline function that reads a line of input from a file descriptor (typically stdin).
• Purpose: Handles user input in the shell, enabling interaction with the program.

9. main.c

• Description: Implements the main function, which is the entry point of the custom shell.
• Purpose: Initializes and runs the shell, managing user input, command parsing, and execution.

10. main.h

• Description: Implements the header file main.h, which contains all necessary prototypes for the shell's functions.
• Purpose: Ensures proper function declaration and code organization throughout the shell program.

11. parser.c

• Description: Implements the _strtok function, a custom version of the strtok function used to tokenize strings.
• Purpose: Used to break down commands and arguments into tokens for easier processing by the shell.

🧪Testing

Your program must replicate the exact behavior of /bin/sh, including error messages.

Error messages must reference the name provided by argv[0].

Example with /bin/sh

$ echo "qwerty" | /bin/sh
/bin/sh: 1: qwerty: not found

Example with your shell

$ echo "qwerty" | ./hsh
./hsh: 1: qwerty: not found

A checker will be provided near the project deadline.

It is strongly recommended to create a full test suite covering both normal and edge cases.

🚀GitHub

Only one repository per group is allowed.

Forking or cloning another group's repository before the deadline may result in a 0% grade.

🧑‍💻Authors

Roullito - GitHub
P-Y74 - GitHub

📝License

This project is part of the curriculum at Holberton School and is intended for educational purposes only.