Question

A process creates a child then it gives it 2 seconds to start in order for the child to register a handler for the SIGTSTP signal and stay alert for receiving the signal. Then the parent reads a command without options from the user and sends it to the child using a pipe then sends SIGTSTP signal to the child. The parent waits after that for the child to terminate then exits. The child handles the SIGTSTP signal by reading a command from the pipe and execute it using execlp system call. Write a C program to implement that logic using the signal handling system not sigaction.   

Answer 1

Please go though code and output.

CODE:

#include <stdio.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>

int main()
{
   int fd[2] = {0}; // pipe fd
   pipe(fd); // genrate fd
   int pid =0;

   pid = fork(); // create child process
   if(pid == 0)
   {
       /* In child process */
       char command[32] = {0};
       read(fd[0], command, sizeof(command)); // read from pipe
       execlp(command, command, NULL); // execute command
       exit(0); // exit child
   }
   else
   {
       char command[32] = {0};
      
       printf("Enter command without opeion: \n");
       scanf("%s",command); // get command from user
       write(fd[1], command, strlen(command)); // write in pipe
       sleep(2); // sleep for 2 seconds
       kill(pid, SIGTSTP); // send SIGTSTP signal to child
       wait(0); // wait for child complition
   }

}

OUTPUT: