Question

Write a C program called test that takes one command line argument, an integer N. When we run test:

./test N

the program will do this:

the parent process forks N child processes

each child process prints its process ID, exits

the parent process waits for all child processes to exit, then exits

Answer 1

Code:

#include <stdio.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <ctype.h>

// function to work with fork
void printer(int n)
{
    // forks n processes
    for(int i=0; i<n; i++)
    {
      int pid = fork();
      // if it is child then print it's id
      if(pid == 0)
      {
        printf("%d ", getpid());
        exit(0);
      }
      // if parent then wait until the child executes
      else
        wait(0);
    }
    // execution of all processes completes
    // Note: This line is optional
    printf("\nAll childs execution completed!!");
}
int main(int argc, char const *argv[])
{
    // print invalid argument if no.of argumets are not 2 and given value is not number
    if(argc != 2 && !isdigit(argv[argc-1]))
    {
        printf("invalid argumets");
        return 0;
    }
    // since, first argumets is string we have to convert it to integer using atoi function
    // then pass it to the printer function
   printer(atoi(argv[argc-1]));
   return 0;
}

Command line argument:

10

Output:

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