linux_pipes.c

#define _GNU_SOURCE /* for pipe2 support */

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <errno.h>
#include <pthread.h>

static int p[2];

static void *
closep0(void *arg) {
    (void)arg;
    sleep(1);
    close(p[0]);
    return NULL;
}

static void *
closep1(void *arg) {
    (void)arg;
    struct timespec t = { 0, 500 * 1000000L };
    nanosleep(&t, NULL);
    close(p[1]);
    return NULL;
}

int
main(int argc, char **argv)
{
    static char buf[16];
    int i, r, opt, closed;
    pthread_t tid[2] = {0};

    closed = 1;
    while ((opt = getopt(argc, argv, "k")) != -1) {
        switch (opt) {
            case 'k':
                closed = 0;
                break;
            default:
                fprintf(stderr, "Usage: %s [-k]\n", argv[0]);
                fprintf(stderr, "\nOptions:\n\t-k to prevent closing write pipe.\n");
                exit(EXIT_FAILURE);
        }
    }

    if (pipe2(p, O_CLOEXEC) != 0) {
        perror("pipe2");
        exit(EXIT_FAILURE);
    }

    if ((r = pthread_create(tid + 0, NULL, closep0, NULL)) != 0) {
        errno = r;
        perror("phtread_create");
        exit(EXIT_FAILURE);
    }

    if (closed && (r = pthread_create(tid + 1, NULL, closep1, NULL)) != 0) {
        errno = r;
        perror("phtread_create");
        exit(EXIT_FAILURE);
    }

    r = read(p[0], buf, sizeof(buf));
    if (r < 0)
        perror("pipe read");
    else if (r == 0)
        puts("Pipe closed");
    else
        printf("what ??? r=%d\n", r);

    for (i = 0; i < 2; i++) {
        if (tid[i] && (r = pthread_join(tid[i], NULL)) != 0) {
            errno = r;
            perror("phtread_join");
            exit(EXIT_FAILURE);
        }
    }

    return 0;
}