Simple Shell

Releade date December 9, 2022.

Table of Contents

1. Introduction
2. Prokect Information
   • Task
   • General Requirements
   • Allowed functions & system calls
3. Documentation
   • Usage
4. Authors

📜 Introduction

• What is Shell?

  Shell is an enviorment in which we can run our commands, programs and shell scripts.

• What is the difference between a function & a system call?

  The main difference between system call and function call is that a system call is a request for the kernel to access a resource while a function call is a request made by a program to perform a specific task. System call are used when a program needs to communicate with the kernel while function call are to call a specific function within the program.

• How does the shell use the PATH to find the programs?

  The PATH variable is basically a list of directories your computer looks through to fing a requested executable.

• How to suspend the execution of a process until one of its children terminates?

  We can suspend the execution of a process until one of its children terminates using the wait function. A call to wait() blocks the calling process until one of its child processes exits or a signal is received. After child process terminates, parent continues its execution after wait system call instruction.

📢 Project Information

🎯 Tasks

• Task 0 - Write a README, Write a man for your shell & AUTHOR file.

• Task 1 - Write a beautiful code that passed the Betty checks

• Task 2 Write a UNIX command line interpreter.

Usage: simple_shell

Your Shell should:

Display a prompt and wait for the user to type a command. A command line always ends with a new line. The prompt is displayed again each time a command has been executed. The command lines are simple, no semicolons, no pipes, no redirections or any other advanced features. The command lines are made only of one word. No arguments will be passed to programs. If an executable cannot be found, print an error message and display the prompt again. Handle errors. You have to handle the “end of file” condition (Ctrl+D)

You don’t have to:

use the PATH implement built-ins handle special characters be able to move the cursor handle commands with arguments

• Task 3 - Handle command lines with arguments

• Task 4 - Handle the PATH, fork must not be called if the command doesnt exist

• Task 5 - Implement the exit built-in, that exits the shell

• Task 6 - Implement the env built-in, that prints the current enviorment

⚒ General requirements

Allowed editors:

All our files were compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89

Language:

✅ Allowed functions & system calls

- 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)
- 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)

🗃️ Documentation

🕹️ Usage

Interactive

An interactive shell is defined as the shell that simply takes commands as input from the user and acknowledges the output to the user. This shell also reads startup files that occurred during activation and display a prompt.

Non-Interactive

As the name inplies, a non-interactive shell is a type of shell that doesn't interact with the user. We can run it through a script. Also, it can be run through some automated process. The non-interactive shell influence the PATH variables. It is higly recommended to use the full path for a command in non-interactive shells. Non-interactive scripts can smoothly run in the background easily.

Built-In

A built-in is a command or function that is part of the shell itself. The command is "built-in" to the shell program - no external program is necessary to run the command, and a new process does not need to be created.

🖋️ Developers

Lizbeth Garcia & Yahdiel Saldaña

Hi, Im Lizbeth Garcia on of the developer behind this project. To connect with me professionaly and explore more about my work, I invite you to visit my LinkedIn profile (Lizbeth Garcia ). There, you can find articles, and professional experiences. For more casual discussion and tech insight, feel free to follow me on Twitter (@GarlebLizz) or Instagram (@CodewithLizz). I look foward to connecting with you!

Hey, Im Yahdiel Saldaña one of the developer behind this project. You can find me on Github (Yahdiel Saldaña