https://github.com/imsatyasaiteja/simple-linux-shell

Simple Linux Shell CLI application
https://github.com/imsatyasaiteja/simple-linux-shell

c-programming execvp getcwd linux-commands linux-shell

Last synced: about 1 month ago
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Simple Linux Shell CLI application

• Host: GitHub
• URL: https://github.com/imsatyasaiteja/simple-linux-shell
• Owner: imsatyasaiteja
• Created: 2022-12-17T13:01:57.000Z (about 2 years ago)
• Default Branch: main
• Last Pushed: 2024-03-10T06:30:17.000Z (10 months ago)
• Last Synced: 2024-03-10T07:30:45.287Z (10 months ago)
• Topics: c-programming, execvp, getcwd, linux-commands, linux-shell
• Language: C
• Homepage:
• Size: 561 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
## Simple Linux Shell

Hey! Here's a Command Line Interface application I've written in C language that works like a Linux shell

### Preview

Here are some important Linux commands that I've tested on my Linux shell application





### Code Explanation

- The _main( )_ function executes a _while_ loop

We need this loop to run the shell input command infinitely after execution of each command

- The _shell_ function does the following job :

  - It stores the user input in the character array _cmd[100]_ (string)

  - length of this string _cmd_ is stored in _l_

- We pass this string cmd and its length _l_ to a token function _tok(cmd,l)_

- The _tok(cmd, l)_ function's return type is a 2D array (an array of strings)

  - This function takes the _cmd_ string and tokenizes it into a group of strings

  - A global variable _g_ is used to store the number of tokens obtained

- The array of strings returned by token function is stored in _a_

- Now, we compare the first token _a[0]_ given by the user with _cd, echo, pwd_, If the token matches with any one of them, its respective function is called :

  - _Cd(a)_ function uses _chdir(a[1])_, an in-built function to change the directory

  - _Echo(a)_ function concats all the tokens from _a[1]_ to _a[g-1]_ and stores in a string _b_

  - A _for_ loop is used to remove _"_ character

  - _Pwd( )_ function uses _getcwd( )_, an in-built function to get the current working directory

  - _Cmd(a)_ function is used to access commands like _mkdir, ls, cat, rm, date_ executables in the bin folder using **_execvp( )_**

	- In this _Cmd(a)_ function, **_fork( )_** function is used to initialize a child process

	- In the child process execvp is used. Its return value is stored in a variable z

	- If _z != 0_, It displays an error

	- _execvp_ takes the input command and the array of strings as arguments

	- _execvp_ function calls the file from bin folder according to the user input

	- Meanwhile, the parent process waits for the child process to exit             

- After leaving the _if-else_ loop and executing one of the _Cd( ), Pwd( ), Echo( ), Cmd( )_ functions, the array a memory is freed

- Because we have a _while_ loop in our Main function and it breaks only when character _ch != '\n'_

- At each step, it calls the shell function again