This is sockets/us_xfr_sv.c (Listing 57-3, page 1168), 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.

This page shows the "distribution" or "book" version of the file (why are there two versions?), or the differences between the two versions. You can switch between the views using the tabs below.

In the listing below, the names of Linux system calls and C library functions are hyperlinked to manual pages from the Linux man-pages project, and the names of functions implemented in the book are hyperlinked to the implementations of those functions.


Download sockets/us_xfr_sv.c

  Cover of The Linux Programming Interface

Function list (Bold in this list means a function is not static)

/* us_xfr_sv.c

   An example UNIX stream socket server. Accepts incoming connections
   and copies data sent from clients to stdout.

   See also us_xfr_cl.c.
#include "us_xfr.h"
#define BACKLOG 5
main(int argc, char *argv[])
    struct sockaddr_un addr;
    int sfd, cfd;
    ssize_t numRead;
    char buf[BUF_SIZE];

    sfd = socket(AF_UNIX, SOCK_STREAM, 0);
    if (sfd == -1)

    /* Construct server socket address, bind socket to it,
       and make this a listening socket */

    /* For an explanation of the following check, see the errata notes for
       pages 1168 and 1172 at */

    if (strlen(SV_SOCK_PATH) > sizeof(addr.sun_path) - 1)
        fatal("Server socket path too long: %s", SV_SOCK_PATH);

    if (remove(SV_SOCK_PATH) == -1 && errno != ENOENT)
        errExit("remove-%s", SV_SOCK_PATH);

    memset(&addr, 0, sizeof(struct sockaddr_un));
    addr.sun_family = AF_UNIX;
    strncpy(addr.sun_path, SV_SOCK_PATH, sizeof(addr.sun_path) - 1);

    if (bind(sfd, (struct sockaddr *) &addr, sizeof(struct sockaddr_un)) == -1)

    if (listen(sfd, BACKLOG) == -1)

    for (;;) {          /* Handle client connections iteratively */

        /* Accept a connection. The connection is returned on a new
           socket, 'cfd'; the listening socket ('sfd') remains open
           and can be used to accept further connections. */

        cfd = accept(sfd, NULL, NULL);
        if (cfd == -1)

        /* Transfer data from connected socket to stdout until EOF */

        while ((numRead = read(cfd, buf, BUF_SIZE)) > 0)
            if (write(STDOUT_FILENO, buf, numRead) != numRead)
                fatal("partial/failed write");

        if (numRead == -1)

        if (close(cfd) == -1)


Download sockets/us_xfr_sv.c

Note that, in most cases, the programs rendered in these web pages are not free standing: you'll typically also need a few other source files (mostly in the lib/ subdirectory) as well. Generally, it's easier to just download the entire source tarball and build the programs with make(1). By hovering your mouse over the various hyperlinked include files and function calls above, you can see which other source files this file depends on.

Valid XHTML 1.1