C - Simple Shell Final Project

This project is a collaboration among three students at Holberton Coding School. Our main goal is to develop a simple UNIX command interpreter that emulates basic shell behavior.

Authors

• Nissel Sanchez
• Luis Marrero
• Emmanuel Torres

Project Description

This project involves creating a simple shell, a basic command line interpreter similar to UNIX shells. It is designed to interpret and execute commands in an interactive mode and non-interactive mode.

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General

• Who designed and implemented the original Unix operating system
• Who wrote the first version of the UNIX shell
• Who invented the B programming language (the direct predecessor to the C programming language)
• Who is Ken Thompson
• How does a shell work
• What is a pid and a ppid
• How to manipulate the environment of the current process
• What is the difference between a function and a system call
• How to create processes
• What are the three prototypes of main
• How does the shell use the PATH to find the programs
• How to execute another program with the execve system call
• How to suspend the execution of a process until one of its children terminates
• What is EOF / "end-of-file"?

Requirements

General

• Allowed editors: vi, vim, emacs
• All your files will be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89
• All your files should end with a new line
• A README.md file, at the root of the folder of the project is mandatory
• Your code should use the Betty style. It will be checked using betty-style.pl and betty-doc.pl
• Your shell should not have any memory leaks
• No more than 5 functions per file
• All your header files should be include guarded
• Use system calls only when you need to (why?)

List of allowed functions and system calls+

• all functions from string.h
• access (man 2 access)
• chdir (man 2 chdir)
• close (man 2 close)
• closedir (man 3 closedir)
• execve (man 2 execve)
• exit (man 3 exit)
• _exit (man 2 _exit)
• fflush (man 3 fflush)
• fork (man 2 fork)
• free (man 3 free)
• getcwd (man 3 getcwd)
• getline (man 3 getline)
• getpid (man 2 getpid)
• isatty (man 3 isatty)
• kill (man 2 kill)
• malloc (man 3 malloc)
• open (man 2 open)
• opendir (man 3 opendir)
• perror (man 3 perror)
• printf (man 3 printf)
• fprintf (man 3 fprintf)
• vfprintf (man 3 vfprintf)
• sprintf (man 3 sprintf)
• putchar (man 3 putchar)
• read (man 2 read)
• readdir (man 3 readdir)
• signal (man 2 signal)
• stat (__xstat) (man 2 stat)
• lstat (__lxstat) (man 2 lstat)
• fstat (__fxstat) (man 2 fstat)
• strtok (man 3 strtok)
• wait (man 2 wait)
• waitpid (man 2 waitpid)
• wait3 (man 2 wait3)
• wait4 (man 2 wait4)
• write (man 2 write)

Compilation

• gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh

Documentation

Files

• env.c: Prints environment variables.
• execute_command.c: Handles input command processing, verifies PATH, checks file accessibility, manages child processes, and utilizes execve for execution.
• my_own_func.c: Custom implementations of standard library functions.
• simple_shell.c: Includes the main function, string parsing, memory management, and built-in commands handling (env, exit).

Usage

Tasks

0. README, man, AUTHORS

Mandatory

• Write a README
• Write a man page for the shell.
• Include an AUTHORS file at the root of the repository, listing all contributors.

1. Betty would be proud

Mandatory

Write code that passes the Betty checks for beautiful code.

2. Simple shell 0.1

Mandatory

Write a UNIX command line interpreter.

3. Simple shell 0.2

Mandatory

Simple shell 0.1 +:

• Handle command lines with arguments

4. Simple shell 0.3

Mandatory

Simple shell 0.2 +:

• Handle the PATH
• Do not call fork if the command doesn’t exist

5. Simple shell 0.4

Mandatory

Simple shell 0.3 +:

• Implement the exit built-in, which exits the shell
• Usage: exit
• No need to handle any argument to the built-in exit

6. Simple shell 1.0

Mandatory

Simple shell 0.4 +:

• Implement the env built-in, which prints the current environment