3sum_fork.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

static long int count(long int *a); // prototype counting function


#ifndef MAX_ELEMENTS
#define MAX_ELEMENTS        10
#endif /* MAX_ELEMENTS */

#ifndef CLOCKS_PER_SEC
#error CLOCKS_PER_SEC not defined on this platform
#endif /* CLOCKS_PER_SEC */


int main(int argc, char **argv) {
  int pid;
  int state;

  long int        arr[MAX_ELEMENTS], i, cnt;
  clock_t         start_time, end_time;
  double          total_time;
  FILE            *fp;

  pid = fork();     // creating child process


  if (pid == 0) {   // starting child process
    printf("my parent's pid = %d\n", getppid());

       switch ( argc ) {
        case 1:
            fp = stdin;
            break;
        case 2:
            if ( (fp = fopen(argv[1], "r")) == NULL ) {
                fprintf(stderr, "Could not open input file: %s\n", strerror(errno));
                return 2;
            };
            break;
        default:
            fprintf(stderr, "Usage: %s [ FILE ]\n", argv[0]);
            return 1;
            break;
    };

    start_time = clock();
    printf("Starting of the program: = %ld\n", start_time);

    for ( i = 0; i < MAX_ELEMENTS; i++ ) { 
        fscanf(fp,"%ld", &arr[i]);
        printf("%ld\n", arr[i]);
    };

    fclose(fp);
    cnt = count(arr);
    end_time = clock();

    printf("Result: %ld\n", cnt);

    total_time = (double)(end_time - start_time) / CLOCKS_PER_SEC;
    printf("Total time taken by CPU: %f\n", total_time);
    return 0;

    _exit(0);     // end child process
  }

  /* Now back to the parent code */
  if (pid < 0) {
    fprintf(stderr, "\tfork failed\n\n");
    _exit(1);
  }

  printf("Child pid = %d\n", pid);

  //wait(&state);     /* wait for the child process to end */
  //printf("The state value is: %d\n ", state);

  //return;
}

static long int count(long int *a) {
  int     counting, i, j, k;


  counting = 0;
  for ( i = 0; i < MAX_ELEMENTS - 2; i++ )
    for ( j = i + 1; j < MAX_ELEMENTS - 1; j++ )
      for ( k = j + 1; k < MAX_ELEMENTS; k++ )
        if ( (a[i] + a[j] + a[k]) == 0 ) {
          counting++;
          printf("Triplet Found : %ld, %ld, %ld\n", a[i], a[j], a[k]);
        };

  return counting;
}