Operating Systems - Projects and Exercises

forkexec.c

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/* 
  forkexec - skeleton program displaying fork and exec use
  
  usage:
  
    forkexec
          
    displays process id of parent and child before and after fork.
    executes the program 'sleepy' in the current directory with a single
    command line argument of 10. ('sleepy' is the program written during
    the first exercise. This call should cause sleepy to print out 10
    seconds of output before terminating)

      
 ********************************************************************
   version: 1.0
   date:    December 2003
   author:  Ian G Graham
            School of Information Technology
            Griffith University, Gold Coast
            ian.graham@griffith.edu.au
            
   copyright (c) Ian G Graham, 2003. All rights reserved.
            
   This code can be used for teaching purposes, but no warranty,
   explicit or implicit, is provided.
 *******************************************************************/
 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
 
extern int errno;        // system error number 
 
void syserr(char* );     // error report and abort routine 
 
int main(int argc, char *argv[])
{
   pid_t pid;            // process ID
   int rc;               // return code
 
   pid = getpid();       // get our own pid
   printf("Process ID before fork: %d\n", (int)pid);
	
   switch (fork()) {
      case -1:
         syserr("fork");
      case 0:             // execution in child process 
         pid = getpid();  // get child pid
         printf("Process ID in child after fork: %d\n", pid);
         execlp("sleepy", "sleepy", "10",NULL);
         syserr("execl"); // error if return from exec
   }
 
// continued execution in parent process
 
   pid = getpid();        // reget our pid
   printf("Process ID in parent after fork: %d\n", pid);
 
   exit(0);
}
 
void syserr(char * msg)   // report error code and abort
{
   fprintf(stderr,"%s: %s", strerror(errno), msg);
   abort(errno);
}

For use only by students and instructors using the supplementary material available with the text book: "Operating Systems - Internals and Design Principles", William Stallings, Prentice Hall, 5th Edition, 2004. Not to be printed out or copied by any other persons or used for any other purpose without written permission of the author(s).

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