This is sockets/us_xfr_v2_sv.c, an example to accompany the book, The Linux Programming Interface.

This file is not printed in the book; it is the solution to Exercise 59-3:d (page 1237).

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

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_v2_sv.c

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

/* us_xfr_v2_sv.c

   An example UNIX stream socket server. Accepts incoming connections and
   copies data sent from clients to stdout. This program is similar to
   us_xfr_sv.c, except that it uses the functions in unix_sockets.c to
   simplify working with UNIX domain sockets.

   See also us_xfr_v2_cl.c.
#include "us_xfr_v2.h"
main(int argc, char *argv[])
    int sfd = unixBind(SV_SOCK_PATH, SOCK_STREAM);
    if (sfd == -1)

    if (listen(sfd, 5) == -1)

    for (;;) {          /* Handle client connections iteratively */
        int cfd = accept(sfd, NULL, NULL);
        if (cfd == -1)

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

        ssize_t numRead;
        char buf[BUF_SIZE];

        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_v2_sv.c

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