holbertonschool-simple_shell

Holberton-simple_shell project, made in November 2022 by 3 students from Holbertonschool-Toulouse #C19.

Simple_shell README

Synopsis:

This project was made in order to code a simplest version of the shell, which is an UNIX interpreter.

This project was realized in 10 days, in order to reproduce work conditions, during the third month of learning with the Holberton School in Toulouse, France.

About the project

For this project we were mandated to produce a simple shell program, writing a simple UNIX command interpreter.

The simple shell had to read commands from the standard input and execute them. The shell invokes the program, specified as command, as a child process.

The project was divided into several tasks in order to implement the program progressively.

At first, the program had to:

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 the “end of file” condition (Ctrl+D)

At the end our simple shell had to handle:

Errors
Command lines with arguments
The PATH
The exit built-in
The env built-in, that prints the current environment

Execute the program

In order to use this simple_shell program, in the interactive mode, it need to be executed in a Shell command terminal.

Follow this steps:

Compile it with this line command: gcc -Wall -Werror -Wextra -pedantic *.c -o hsh
Run it with: ./hsh
You can now run some command in the simple shell, if you want to exit it type this command line: Ctrl + c, Ctrl + d or exit.

Output

Some instructions we had to follow about the output:

Unless specified otherwise, your program must have the exact same output as sh (/bin/sh) as well as the exact same error output.
The only difference is when you print an error, the name of the program must be equivalent to your argv[0] (See below).

Example of error with sh:

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

Same error with your program hsh:

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

List of allowed functions and system calls

We were allowed to use the following c functions and 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)

Our code was compiled this way : $ gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh

Testing

Our shell should work like this in interactive mode:

($) /bin/ls
hsh main.c shell.c
($)
($) exit
$

But also in non-interactive mode:

hsh main.c shell.c test_ls_2
$
$ cat test_ls_2
/bin/ls
/bin/ls
$
$ cat test_ls_2 | ./hsh
hsh main.c shell.c test_ls_2
hsh main.c shell.c test_ls_2
$

Built with

Language: C
Text editor: Vim
Docker.

Description of the simple shell

The simple shell is a copy of the UNIX shell, wich is an interactive user interface with an operating system.

The program understands and executes the commands entered by the user as input, and give results as output.

To performs a command or an executable in shell, there is 3 steps:

The simple shell read and execute its configuration files, to change the shell's behavior
The commands are read from stdin and executes them
After command execution, the simple shell make any shutdown commands, frees up the memory allocations and terminates processes.

Usage

The simple shell is a command interpreter used to communicate with the Unix system.

Manual Page

We have created a Manpage to to accompany the user.

Manpage

Project Files Description

The projects include 6 files as follows: (to update withe the finals docs)

_getenv.c - Function _getenv to get environment variable.
free_malloc.c - Function free_malloc that free all dynamic allocation memory during the hsh.c programm.
print_full_env.c - Function print_full_env.c that execute command buildin "env".
hsh.c - Main function for simple shell project that include functions split_string, execve_cmd, _which and loop_getline.