Mpifork.c

#include <sys/types.h>
#include <unistd.h>
#include <stdio.h>
#include <math.h>
#include <mpi.h>
void main(int argc, char *argv[])
{
  /*################################################*/
  /*                                                */
  /*           *****************                    */
  /*           * OASIS ROUTINE *                    */
  /*           * ------------- *                    */
  /*           *****************                    */
  /*                                                */
  /* program which launches couple, atmos and ocean */
  /* Author: Claude Mercier, Laurent Terray         */
  /* Updated: Ingo Bethke (2012.05.05)              */
  /* ------                                         */
  /*################################################*/
  int id1, id2, rtc;

  /* IO variables. */
  FILE *file_ptr;
  int masterpid=100000000, pid, status, i;
  unsigned int sleeplen;

     /* write process id to common file */
     pid=getpid();
     file_ptr=fopen("pid.txt","a");
     fprintf(file_ptr,"%d\n",(int) getpid());
     fclose(file_ptr);

     /* wait a second to make sure that all ids are written */  
     sleeplen=1;
     sleep(sleeplen);

     /* read process id from all processes and check if
        this process is the master process (i.e., has lowest id) */
     file_ptr=fopen("pid.txt","r");
     while(!feof(file_ptr)) {
        fscanf(file_ptr, "%d", &pid);
        if (pid < masterpid) {
           masterpid=pid;
        }
     }
     fclose(file_ptr);

     if (masterpid == getpid()){
        printf("master pid %d\n",masterpid); 
        id1 = fork();

        if(id1 == -1) {
          perror("first FORK failed");
          exit(1);
        }

        if(id1 != 0) {
          /* parent */
          id2 = fork();
          if(id2 == -1) {
            perror("second FORK failed");
            exit(2);
          }
           sleep(5);
           if (id2 != 0) {
            /* still the parent */
            /*coupler*/
               printf("Launch oasis %d\n",getpid());
               rtc = execl("arpege","arpege",0);
               perror("EXEC 1 failed");
          } else {
            /* child 2 */
            printf("Launch arpege %d\n",getpid()); 
            execl("oasis","oasis",0);
            perror("EXEC 2 failed");
          }
        } else {
           /* child 1 */
           printf("Launch micom %d\n",getpid());
           execl("micom","micom",0);
           perror("EXEC 3 failed");
        }
     } else {
          printf("Launch arpege %d\n",getpid());    
        execl("arpege","arpege",0);
        perror("EXEC 2 failed");
     }
}