sockets/us_abstract_bind.c

This is sockets/us_abstract_bind.c (Listing 57-8, page 1176), an example from the book, The Linux Programming Interface.

The source code file is copyright 2024, 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.

  Cover of The Linux Programming Interface
+/* us_abstract_bind.c
+
+   Demonstrate how to bind a UNIX domain socket to a name in the
+   Linux-specific abstract namespace.
+
+   This program is Linux-specific.
+
+   The first printing of the book used slightly different code. The code was
+   correct, but could have been better (to understand why, see the errata
+   for page 1176 of the book).  The old code is shown in comments below.
+*/
 #include <sys/un.h>
 #include <sys/socket.h>
 #include "tlpi_hdr.h"
 
 int
 main(int argc, char *argv[])
 {
     int sockfd;
     struct sockaddr_un addr;
     char *str;
 
     memset(&addr, 0, sizeof(struct sockaddr_un));  /* Clear address structure */
     addr.sun_family = AF_UNIX;                     /* UNIX domain address */
 
     /* addr.sun_path[0] has already been set to 0 by memset() */
 
     str = "xyz";        /* Abstract name is "\0xyz" */
     strncpy(&addr.sun_path[1], str, strlen(str));
 
+    // In early printings of the book, the above two lines were instead:
+    //
+    // strncpy(&addr.sun_path[1], "xyz", sizeof(addr.sun_path) - 2);
+    //            /* Abstract name is "xyz" followed by null bytes */
+
     sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
     if (sockfd == -1)
         errExit("socket");
 
     if (bind(sockfd, (struct sockaddr *) &addr,
             sizeof(sa_family_t) + strlen(str) + 1) == -1)
         errExit("bind");
 
+    // In early printings of the book, the final part of the bind() call
+    // above was instead:
+    //        sizeof(struct sockaddr_un)) == -1)
+
     sleep(60);
 
     exit(EXIT_SUCCESS);
 }

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