dr8co / simple_shell

A simple UNIX shell implemented in C.

Simple_Shell

Table of Content

• About
• Rules
  • General Rules
  • Output
  • Allowed Functions and system calls
• Checks
• Compilation
  • Requirements
  • How to compile
• Samples
• Authors

About

This project is an implementation of a simple shell for UNIX-like systems.

It was done in fulfilment of the ALX Software Engineering Programme's syllabus.

Rules

General Rules

• All files to be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89.
• Code should use Betty style
• Your shell should not have any memory leaks
• No more than 5 functions per file
• Use system calls only when you need to
• All header files should be include-guarded
• All files should end with a new line
• You should have an AUTHORS file at the root of your repository, listing all individuals having contributed content to the repository.

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]

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)
• 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)

Checks

✔️ Write a beautiful code that passes the Betty checks
✔️ Handle command lines with arguments
✔️ Handle the PATH
✔️ Implement the exit built-in, that exits the shell
✔️ Write your own getline function
✔️ You are not allowed to use strtok
✔️ Implement the builtin command cd
✔️ Handle variables replacement
✔️ Handle comments (#)
✔️ Your shell can take a file as a command line arguments

Compilation

Requirements

• Ubuntu 20.04 LTS
• GCC compiler

How to compile

The source files to be compiled using -Wall -Werror -Wextra -pedantic -std=gnu89 flags.

The samples below illustrate the usage and compilation.

Samples

ian@github:~/shell$ gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o simple_shell
ian@github:~/shell$ ./simple_shell

$ env
USER=ian
LANGUAGE=en_US
SESSION=ubuntu
COMPIZ_CONFIG_PROFILE=ubuntu
SHLVL=1
HOME=/home/ian
C_IS=Fun_:)
DESKTOP_SESSION=ubuntu
LOGNAME=ian
TERM=xterm-256color
PATH=/home/julien/bin:/home/julien/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
DISPLAY=:0
$ /bin/ls
barbie_j       env-main.c  exec.c  fork.c  pid.c  ppid.c    prompt   prompt.c  shell_0.3  stat    test_scripting.sh  wait.c
env-environ.c  exec    fork    mypid   ppid   printenv  promptc  shell     shell.c    stat.c  wait
$ ls
barbie_j       env-main.c  exec.c  fork.c  pid.c  ppid.c    prompt   prompt.c  shell_0.3  stat    test_scripting.sh  wait.c
env-environ.c  exec    fork    mypid   ppid   printenv  promptc  shell     shell.c    stat.c  wait
$ ls -l /tmp 
total 20
-rw------- 1 julien julien    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 julien julien    0 Dec  5 12:09 unity_support_test.0
$ ^C

ian@github:~/shell$

Author(s)

Ian Duncan.