C - Simple Shell

C Group Project Syscall

This group project describes a simple UNIX command interpreter based on bash and Sh It implements some of the functionalities of the original bash shell such as; listing, searching in the path variable, exit and env builtins, among others. It is built for learning purposes and as a required project for Alx Software Engineering curriculum

Description

This is a shell written in C.
It is based on The Thompson Shell.

Essential Functionalities of the Simple Shell:

Displays a prompt "#cisfun$ " and waits for user input.
Runs all commands of type "executable program" (ls and /bin/ls).
Runs the following build_in commands: exit, env, setenv and unsetenv.
Handles commands with arguments.
Handles the PATH global variable.
Handles The EOF (End Of File) condition.
Handles the Ctrl + C signal -> It doesn't exit the shell

Functions

• AUTHORS -> List of contributors to this repository
• man_1_simple_shell -> Manual page for the simple_shell
• shell.h -> Header file
• shell.c -> main function
  • sig_handler -> handles the Ctrl + C signal
  • _EOF -> handles the End Of File condition
• string.c
  • _putchar -> prints a character
  • _puts -> prints a string
  • _strlen -> gives the length of a string
  • _strdup -> copies a string in a newly allocated memory
  • concat_all -> concatenates 3 strings in a newly allocated memory
• line_exec.c
  • splitstring -> splits a string into an array of words
  • execute -> executes a command using execve
  • realloc -> reallocates a memory block
  • freearv -> frees a 2 dimensional array
• linkpath.c
  • _getenv -> returns the value of a global variable
  • add_node_end -> adds a node in a singly linked list
  • linkpath -> creates a singly linked list for PATH directories
  • _which -> finds the pathname of a command
  • free_list -> frees the linked list of PATH value
• checkbuild.c
  • checkbuild -> checks if a command is a build-in command
• buildin.c
  • exitt -> handles the exit buildin command
  • _atoi -> converts a string into an integer
  • env -> prints the current environment
  • _setenv -> Initialize a new global variable, or modify an existing one
  • _unsetenv -> remove a global variable

---

List of allowed functions and system calls for this project

• 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)
• 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)

Installation

Clone the below repository and compile the files into an executable using the GCC compiler.

https://github.com/daveeazi/simple_shell.git.

Environment

Our shell was built and tested on Ubuntu 20.04 LTS.

Basic usage 💡

• First, fork this repository.
• Then clone it to your local machine.
• Create an executable by running the following command:
• Type cd simple_shell
• gcc -Wall -Werror -Wextra -pedantic *.c -o hsh
• From there, type in the following command and press your enter button.
• ./hsh
• When you want to exit the shell, you can use one of the following methods:

1: Type the command "exit"

exit

2: Press on Ctrl + D

• Final step: ENJOY!

Example 💻

ubunto@ubuntu:~/OS/simple_shell$ gcc -Wall -Wextra -Werror -pedantic *.c -o hsh
ubunto@ubuntu:~/OS/simple_shell$ ./hsh
#cisfun$ echo Hello, This is an example
Hello, This is an example
#cisfun$ ls
README.md  checkbuild.c  line_exec.c  shell.c  string.c
buildin.c  hsh		 linkpath.c   shell.h
#cisfun$ ^C
#cisfun$ ls -l
total 52
-rw-r--r-- 1 ubunto ubunto  3067 Aug 9 04:22 README.md
-rw-r--r-- 1 ubunto ubunto  2183 Aug 9 16:17 buildin.c
-rw-r--r-- 1 ubunto ubunto   574 Aug 9 15:59 checkbuild.c
-rwxr-xr-x 1 ubunto ubunto 18144 Aug 9 04:22 hsh
-rw-r--r-- 1 ubunto ubunto  2091 Aug 9 14:49 line_exec.c
-rw-r--r-- 1 ubunto ubunto  199 Aug 9 14:30 linkpath.c
-rw-r--r-- 1 ubunto ubunto   951 Aug 9 16:09 shell.c
-rw-r--r-- 1 ubunto ubunto  1351 Aug 9 15:58 shell.h
-rw-r--r-- 1 ubunto ubunto  1727 Aug 9 14:30 string.c
#cisfun$ exit
ubunto@ubuntu:~/OS/simple_shell$

Help

If you need help to get started with hsh simple shell, email one of the contributers as listed in AUTHORS.

Authors

• David Atat Mail at: [email protected]
• Alphonsus Oshiole Mail at [email protected]

Acknowledgments

• Our fellow cohort members.
• The creators of the C language.
• Our software engineer-in-residence.
• Betty, Alx Holberton.