This is pipes/fifo_seqnum_client.c (Listing 44-8, page 914), an example from the book, The Linux Programming Interface.

The source code file is copyright 2022, Michael Kerrisk, and is licensed under the GNU General Public License, version 3.

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#include "fifo_seqnum.h"

static char clientFifo[CLIENT_FIFO_NAME_LEN];
static void             /* Invoked on exit to delete client FIFO */
main(int argc, char *argv[])
    int serverFd, clientFd;
    struct request req;
    struct response resp;

    if (argc > 1 && strcmp(argv[1], "--help") == 0)
        usageErr("%s [seq-len]\n", argv[0]);

    /* Create our FIFO (before sending request, to avoid a race) */

    umask(0);                   /* So we get the permissions we want */
            (long) getpid());
    if (mkfifo(clientFifo, S_IRUSR | S_IWUSR | S_IWGRP) == -1
                && errno != EEXIST)
        errExit("mkfifo %s", clientFifo);

    if (atexit(removeFifo) != 0)

    /* Construct request message, open server FIFO, and send message */

    req.pid = getpid();
    req.seqLen = (argc > 1) ? getInt(argv[1], GN_GT_0, "seq-len") : 1;

    serverFd = open(SERVER_FIFO, O_WRONLY);
    if (serverFd == -1)
        errExit("open %s", SERVER_FIFO);

    if (write(serverFd, &req, sizeof(struct request)) !=
            sizeof(struct request))
        fatal("Can't write to server");

    /* Open our FIFO, read and display response */

    clientFd = open(clientFifo, O_RDONLY);
    if (clientFd == -1)
        errExit("open %s", clientFifo);

    if (read(clientFd, &resp, sizeof(struct response))
            != sizeof(struct response))
        fatal("Can't read response from server");

    printf("%d\n", resp.seqNum);


Download pipes/fifo_seqnum_client.c

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