Simple Shell

Building a shell

Description

This repository contains a team project made by Holberton School students. Here you are going to find a simple UNIX command interpreter (a shell), written in C language. With this interpreter, you can read command lines, interpret them, run them, print the environment of the shell, and exit it.

Files description

• shell.h Header file that contains the libraries, the prototypes of all functions and the global variable environ.
• main.c It contains a call to the shell_loop function to use it.
• shell_loop.c Function that creates an infinite loop and displays the prompt of the simple shell, where the user can write the command lines and the shell executes them. The file calls 3 different functions.
• function_getline.c This function gets the command line introduced by the user using getline
• function_arguments.c The function splits the command line into tokens using strtok
• execute_command.c This function executes all the commands in interactive or non-interactive mode, using the root or the executable file of the command (see usage -output on this file for more info). The function includes the exit built-in function and the env, where the environment variables are stored.
• aux_functions.c The file includes 4 auxiliar functions. _strcmp to compare 2 strings, _strlen to know the length of a string, _strncat to concatenate 2 strings, and _printf to print characters, strings or numbers.
• _putchar.c Function that writes a character to stdout.
• printf_functions.c The file includes 3 auxiliar functions to the _printf function. print_string to write strings, print_character to write a character, and print_integer to write digits.
• man_1_simple_shell This file contains the manual pages of the simple shell. Usage: man ./man_1_simple_shell
• AUTHORS The file contains a list of all individuals having contributed content to the repository in Docker format.

Features

The simple shell has the exact same output as sh (/bin/sh) as well as the exact same error output. For more info type man sh in your terminal or run sh. The sh and the simple shell have an interactive mode (when you run the shell first and then give it the command lines) and a non-interactive mode (when the user give the command lines and runs the shell at the same time, in this mode the user can run one command at a time and the shell doesn't stay running).

• man sh to learn more.

Usage

0. Output

• Output in interactive mode. The simple shell works like this in interactive mode:

$ ./hsh
$ /bin/ls
hsh main.c shell_loop.c shell.h
$
$ exit

• The shell also works by calling the executable file of the command instead of the root. See the example in interactive mode below:

$ ./hsh
$ ls
hsh main.c shell_loop.c shell.h
$
$ exit

• The simple shell works in non-interactive mode as well and the output looks like this:

$ echo "/bin/ls" | ./hsh
hsh main.c shell_loop.c shell.h

• The output in non-interactive mode by calling the executable file:

$ echo "ls" | ./hsh
hsh main.c shell_loop.c shell.h

1. Error message

As with the output, there are 2 possibilities with the error messages.

• In interactive mode the error message looks like this:

$ ./hsh
$ qwerty
hsh: 1: qwerty: not found
$

• In non-interactive mode like this:

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

2. Commands

Below you will find a list of some commands to run in the simple shell.

• ls command to list information about the FILEs in the current directory. Usage: ls or /bin/ls This command takes arguments. Example: ls -l
• pwd This command prints the name of current/working directory Usage: pwd
• cat Command that concatenates files and prints on the standard output. usage: cat filename
• cp This command copies files. Usage: cp sourcefile destfile
• rm Command that removes files Usage: rm filemane
• exit Function that causes normal process termination. Usage: exit
• env Function that runs a program in a modified environment Usage: env
• EOF Indicator or flag that there is no more information to retrieve from a data source. Usage: Ctrl + d

Used functions and sys calls

Function/ sys call	For help
access	man 2 access
execve	man 2 execve
exit	man 3 exit
fork	man 2 fork
free	man 3 free
getline	man 3 getline
isatty	man 3 isatty
strtok	man 3 strtok
wait	man 2 wait
write	man 2 write

Installation

To install and run the simple shell in your machine, clone this repository and compile all the .c files as shown below:

• Link to clone : https://github.com/Carolinacapote/simple_shell.git
• Compile like this: gcc -Wall -Werror -Wextra -pedantic *.c -o hsh

Support and Authors

Type man ./man_1_simple_shell in your terminal to display the manual pages of the simple shell, or you can also contact the authors of the repository via e-mail. :computer:

Name	E-mail adress	GitHub username
Carolina Capote	2621@holbertonschool.com	Carolinacapote
Luis Eduardo Pacheco	2645@holbertonschool.com	lepc7219
Juan David Tuta	2753@holbertonschool.com	Juand0145