/* fork.c */

/* create a child process */

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

int main()
{
  pid_t pid;    /* process id (int) */

  pid = fork();  /* create a child process */

  if ( pid < 0 )
  {
    /* parent unable to produce a child */
    fprintf( stderr, "ERROR: unable to fork()\n" );
    return EXIT_FAILURE;
  }

  /* both parent and child processes return to this point of the code */

  if ( pid == 0 )   /* child process */
  {
    printf( "CHILD: happy birthday!\n" );
    sleep( 5 );
    printf( "CHILD: bye bye\n" );
  }
  else /* pid > 0 so we're in the parent process */
  {
    printf( "PARENT: my child pid is %d\n", pid );
    wait( NULL );  /* wait for the child to terminate */
    printf( "PARENT: my child's done with his/her work\n" );
  }

  return EXIT_SUCCESS;
}