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C - Simple Shell

Table of Contents

Objective

Write a simple UNIX command language interpreter.

Description

The "C - Simple Shell" project is about creating our own simplified version of the [shell]. Shell is a program taking commands from the keyboard and giving them to the operating system to perform.

It consists of a command line interface (CLI) (as opposed to a graphical user interface(GUI) available on most computer nowadays). Most Linux systems provide a program call bash (standing for Bourne Again SHell) an enhanced version of the original Unix shell program, sh, written by Steve Bourne, and acting a the shell program.

Requirements

  • Allowed editors: vi, vim, emacs
  • All files will be compiled on Ubuntu 20.04 LTS
  • Code must follow the Betty style
  • All your files should end with a new line
  • A README.md file, at the root of the folder of the project is mandatory
  • Your shell should not have any memory leaks
  • No more than 5 functions per file
  • No more than functions per file
  • All your header files should be include guarded

Compilation command

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh

Mandatory Tasks

Task 0. README, man, AUTHORS

  • Write a README
  • Write a man for your shell.
  • You should have an AUTHORS file at the root of your repository, listing all individuals having contributed content to the repository.
julien@ubuntu:~/shell$ ./shell 
#cisfun$ ls
./shell: No such file or directory
#cisfun$ /bin/ls
barbie_j       env-main.c  exec.c  fork.c  pid.c  ppid.c    prompt   prompt.c  shell.c  stat.c         wait
env-environ.c  exec    fork    mypid   ppid   printenv  promptc  shell     stat test_scripting.sh  wait.c
#cisfun$ ^[[D^[[D^[[D
./shell: No such file or directory
#cisfun$ ^[[C^[[C^[[C^[[C
./shell: No such file or directory
#cisfun$ exit
./shell: No such file or directory
#cisfun$ ^C
julien@ubuntu:~/shell$ echo "/bin/ls" | ./shell
barbie_j       env-main.c  exec.c  fork.c  pid.c  ppid.c    prompt   prompt.c  shell.c  stat.c         wait
env-environ.c  exec    fork    mypid   ppid   printenv  promptc  shell     stat test_scripting.sh  wait.c
julien@ubuntu:~/shell$

Task 1. Betty would be proud

  • Write a beautiful code that passes the Betty checks

Task 2. Simple shell 0.1

  • Write a UNIX command line interpreter.

    • Usage: ./hsh

  • 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

execve will be the core part of your Shell, don’t forget to pass the environ to it…

julien@ubuntu:~/shell$ ./shell
#cisfun$ ls
./shell: No such file or directory
#cisfun$ /bin/ls
barbie_j       env-main.c  exec.c  fork.c  pid.c  ppid.c    prompt   prompt.c  shell.c  stat.c         wait
env-environ.c  exec    fork    mypid   ppid   printenv  promptc  shell     stat test_scripting.sh  wait.c
#cisfun$ ^[[D^[[D^[[D
./shell: No such file or directory
#cisfun$ ^[[C^[[C^[[C^[[C
./shell: No such file or directory
#cisfun$ exit
./shell: No such file or directory
#cisfun$ ^C
julien@ubuntu:~/shell$ echo "/bin/ls" | ./shell
barbie_j       env-main.c  exec.c  fork.c  pid.c  ppid.c    prompt   prompt.c  shell.c  stat.c         wait
env-environ.c  exec    fork    mypid   ppid   printenv  promptc  shell     stat test_scripting.sh  wait.c
julien@ubuntu:~/shell$

Task 3. Simple shell 0.2

  • Simple shell 0.1 +

    • Handle command lines with arguments

Task 4. Simple shell 0.3

  • Simple shell 0.2 +

    • Handle the PATH
    • fork must not be called if the command doesn’t exist
julien@ubuntu:~/shell$ ./shell_0.3
:) /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
julien@ubuntu:~/shell$

Task 5. Simple shell 0.4

  • Simple shell 0.3 +

    • Implement the exit built-in, that exits the shell
    • Usage: exit
    • You don’t have to handle any argument to the built-in exit

Task 6. Simple shell 1.0

  • Simple shell 0.4 +

    • Implement the env built-in, that prints the current environment
julien@ubuntu:~/shell$ ./simple_shell
$ env
USER=julien
LANGUAGE=en_US
SESSION=ubuntu
COMPIZ_CONFIG_PROFILE=ubuntu
SHLVL=1
HOME=/home/julien
C_IS=Fun_:)
DESKTOP_SESSION=ubuntu
LOGNAME=julien
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
$ exit
julien@ubuntu:~/shell$

Flowchart

Flowchart image for our Simple shell program

Man page

Run man ./man_1_simple_shell

Installation

Install and run:

To install and run Simple Shell, follow these steps:

Clone the repository using the following command:

git clone https://github.com/mistWil/holbertonschool-simple_shell.git

Navigate to the directory where the repository was cloned.

Compile the program by running the following command:

gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o .hsh

Run the program by typing the following command:

./hsh

Using the Simple Shell:

To use our Simple Shell, type a command and press Enter.

The program will execute the command and display the output on the screen.

Here are some examples of commands that you can run:

  • ls: list the contents of the current directory.
  • pwd: print the path of the current working directory.
  • echo: display a message on the screen.
  • mkdir: create a new directory.
  • exit: exit the shell.

Thanks

Many warm thanks to all the Holberton School peers who helped and brought joy throughout the many challenges of this project.

Authors

Julie Dedieu [email protected] Wilfried Leroulier [email protected]