sockets/unix_sockets.c

This is sockets/unix_sockets.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:b (page 1237).

The source code file is copyright 2010, Michael Kerrisk, and is licensed under the GNU Lesser 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/unix_sockets.c

  Cover of The Linux Programming Interface

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

/* unix_sockets.c

   A package of useful routines for UNIX domain sockets.
*/
#include "unix_sockets.h"       /* Declares functions defined here */
#include "tlpi_hdr.h"
/* Build a UNIX domain socket address structure for 'path', returning
   it in 'addr'. Returns -1 on success, or 0 on error. */

int
unixBuildAddress(const char *path, struct sockaddr_un *addr)
{
    if (addr == NULL || path == NULL) {
        errno = EINVAL;
        return -1;
    }

    memset(addr, 0, sizeof(struct sockaddr_un));
    addr->sun_family = AF_UNIX;
    if (strlen(path) < sizeof(addr->sun_path)) {
        strncpy(addr->sun_path, path, sizeof(addr->sun_path) - 1);
        return 0;
    } else {
        errno = ENAMETOOLONG;
        return -1;
    }
}
/* Create a UNIX domain socket of type 'type' and connect it
   to the remote address specified by the 'path'.
   Return the socket descriptor on success, or -1 on error */

int
unixConnect(const char *path, int type)
{
    struct sockaddr_un addr;

    if (unixBuildAddress(path, &addr) == -1)
        return -1;

    int sd = socket(AF_UNIX, type, 0);
    if (sd == -1)
        return -1;

    if (connect(sd, (struct sockaddr *) &addr,
                sizeof(struct sockaddr_un)) == -1) {
        int savedErrno = errno;
        close(sd);                      /* Might change 'errno' */
        errno = savedErrno;
        return -1;
    }

    return sd;
}
/* Create a UNIX domain socket and bind it to 'path'.
   Return the socket descriptor on success, or -1 on error. */

int
unixBind(const char *path, int type)
{
    struct sockaddr_un addr;

    if (unixBuildAddress(path, &addr) == -1)
        return -1;

    int sd = socket(AF_UNIX, type, 0);
    if (sd == -1)
        return -1;

    if (bind(sd, (struct sockaddr *) &addr, sizeof(struct sockaddr_un)) == -1) {
        int savedErrno = errno;
        close(sd);                      /* Might change 'errno' */
        errno = savedErrno;
        return -1;
    }

    return sd;
}

 

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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.

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