Simple Shell

Introduction

This repository is a shell like sh (Bourne Shell) by Stephen Bourne , in C

The goal in this project was to make us understand how a shell works. To single out some items: what is the environment, the difference between functions and system calls, how to create processes using execve...

Usage

In order to run this program,

Clone This Repo

git clone https://github.com/CliffordKasera/simple_shell

compile it with

gcc 4.8.4 -Wall -Werror -Wextra -pedantic *.c -o hsh.
You can then run it by invoking ./hsh in that same directory.

How to use it

In order to use this shell, in a terminal, first run the program:
prompt$ ./hsh
It wil then display a simple prompt and wait for commands.
$
A command will be of the type $ command
This shell can handle two types of commands: builtins and normal program.

List of built-ins

Currently the list of built-ins I wrote is:

cd [directory]
Switch to the specified directory (path).
env
Displays the environment variable
exit [exitstatus]
Exit from the program with exitstatus value. 0 by default.
getenv NAME
Return the value of the NAME variable if it is in the environment
help [command]
Displays the syntax for the command, or all commands.
history
Displays the last typed user .
echo [$$] or [$?] or [$PATH] Return pid and exit statue and PATH.

Command

Basicly Every Program in $PATH It Support Single Word like ls

It Handle Path ls /tmp

it Handle Options Like ls -l

it Handle All Three Togther Like ls -l /var

it Handle Command Path Also Like /bin/ls And All The Option And Path Like /bin/ls -l /var

it Handle Comments #

Examples Command

Example 1

Username@your-regular-prompt:~$ ./hsh
$ pwd
/home/username/
$ ^D
Username@your-regular-prompt:~$

Example 2

Username@your-regular-prompt:~$ ./hsh
$ ls -l /tmp 
-rw------- 1 username username    0 Dec  5 12:09 config-err-aAMZrR
drwx------ 3 root   root   4096 Dec  5 12:09 systemd-private-062a0eca7f2a44349733e78cb4abdff4-colord.service-V7DUzr
drwx------ 3 root   root   4096 Dec  5 12:09 systemd-private-062a0eca7f2a44349733e78cb4abdff4-rtkit-daemon.service-ANGvoV
drwx------ 3 root   root   4096 Dec  5 12:07 systemd-private-062a0eca7f2a44349733e78cb4abdff4-systemd-timesyncd.service-CdXUtH
-rw-rw-r-- 1 username username    0 Dec  5 12:09 unity_support_test.0
$ ^D
Username@your-regular-prompt:~$

Exmples Builtin

case env and exit

Username@your-regular-prompt:~$ ./hsh
USER=Anon
LANGUAGE=en_US
SESSION=ubuntu
COMPIZ_CONFIG_PROFILE=ubuntu
SHLVL=1
HOME=/home/Anon
C_IS=Fun_:)
DESKTOP_SESSION=ubuntu
LOGNAME=Anon
TERM=xterm-256color
PATH=/home/Anon/bin:/home/Anon/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
DISPLAY=:0
$ exit
Username@your-regular-prompt:~$

Case Exit Statue

Username@your-regular-prompt:~$ ./hsh
$ exit 98
Username@your-regular-prompt:~$ echo $?
98
Username@your-regular-prompt:~$

Keep Exploring The echo Builtin and history ... Using The Help Builtin

Also

Handle Ctrl+C: your shell should not quit when the user inputs ^C
If no argument is given to cd the command must be interpreted like cd $HOME
handle the command cd -
Handle variables replacement
Handle the $? variable
Handle the $$ variable
Handle The Argument file like ./hsh test Where test is a file filled with command and builtin to excute.

List of functions and system calls we could use

List of allowed 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)
fork (man 2 fork)
free (man 3 free)
fstat (man 2 fstat)
getcwd (man 3 getcwd)
getline (man 3 getline)
kill (man 2 kill)
lstat (man 2 lstat)
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 (man 2 stat)
strtok (man 3 strtok)
wait (man 2 wait)
waitpid (man 2 waitpid)
wait3 (man 2 wait3)
wait4 (man 2 wait4)
write (man 2 write)
_exit (man 2 _exit)

Custom Function (Recreation of Standard Function in C)

_strncpy
_strlen
_putchar
_atoi
_puts
_strcmp
_isalpha
array_rev
intlen
_itoa
_strcat
_strcpy
_strchr
_strncmp
_strdup
_memcpy
_calloc
_realloc
_getenv
_getline
_strtok

For More Info About It Check The Man Page by

Username@your-regular-prompt:~$ man ./man_1_simple_shell

Project Done in 15 Day

CliffordKasera/simple_shell