Aim:

C program that creates a child process to read commands from the standard input and execute them (a minimal implementation of a shell-like program). You can assume that no arguments will be passed to the commands to be executed.

Description:

fork():it is a system call which forks a new child of a processs

system ():it is a system call which takes a command as an argument and invokes the operating system to execute it.

Code:

include<stdio.h>
include<stdlib.h>
include<sys/types.h>
int main()
  {
  char cmd[20];
  system("clear");
  do{
    printf("[PROMPT]$\n");
    gets(cmd);
    system(cmd);
    }while(strcmp(cmd,"exit"));
}

Output:

/a.out

[PROMPT]$ echo "Hello world"

Hello world!

[PROMPT]$ date

Wed Oct 29 21:40:20 IST 2014

[PROMPT]$ exit