1 /**

     2  * pipe.c

     3  * Copyright (C) 2009 Markus Broeker

     4  *

     5  */

     6 

     7 #include <stdio.h>

     8 #include <stdlib.h>

     9 #include <unistd.h>

    10 #include <wait.h>

    11 #include <assert.h>

    12 

    13 #define MAX 50

    14 

    15 int main (int argc, char **argv)

    16 {

    17     int tube[2];

    18     int i, status, count = 0;

    19 

    20     pid_t pid;

    21 

    22     char buffer[80];

    23 

    24     for (i = 0; i < MAX; i++) {

    25         if (pipe (tube) == -1) {

    26             perror ("PIPE");

    27 

    28             return EXIT_FAILURE;

    29         }

    30 

    31         pid = fork ();

    32         switch (pid) {

    33         case 0:

    34             // we only want to write

    35             close (tube[0]);

    36 

    37             /**

    38              * copy on write: every forked process gets its own copy of i

    39              *                and the magic of synchronization works

    40              */

    41             for (i = 0; i < MAX; i++)

    42                 status = write (tube[1], "MESSAGE FROM SON\n", 17);

    43             break;

    44 

    45         case -1:

    46             printf ("ERROR");

    47             break;

    48 

    49         default:

    50             printf ("Son started as pid %d\n", pid);

    51 

    52             // we only want to read...

    53             close (tube[1]);

    54 

    55             FILE *f = fdopen (tube[0], "r");

    56             assert (f != NULL);

    57             while (fgets (buffer, sizeof (buffer), f) != NULL) {

    58                 printf ("FATHER RECEIVED [%4d]: %s", count++, buffer);

    59             }

    60 

    61             if (fclose (f) < 0)

    62                 perror ("fclose");

    63 

    64             printf ("PID [%4d] has finished...\n", wait (&pid));

    65         }

    66     }

    67 

    68     return EXIT_SUCCESS;

    69 }