gistfile1.c

void sorter(int processes, pid_t *pids, int toSort[][2], int fromSort[][2])
{

        int i, j;

        for (i = 0; i < processes; i++) {
                switch (pids[i] = fork()) {

                case -1: /* Error making shild */
                        perror("creating child");
                        exit(EXIT_FAILURE);

                case 0: /* Setup child before exec */
                        /* Cleanup all unneeded FDs */
                        for (j = 0; j < processes; j++) {
                                close(toSort[j][1]);
                                close(fromSort[j][0]);
                                if (j == i) {
                                        dup2(toSort[j][0], STDIN_FILENO);
                                        dup2(fromSort[j][1], STDOUT_FILENO);
                                } else {
                                        close(toSort[j][0]);
                                        close(fromSort[j][1]);
                                }
                        }
                        execlp("sort", "sort", (char*) NULL);

                default:
                        break;
                }
        }
}