This is filesys/t_mount.c (Listing 14-1, page 268), an example program file from the book, The Linux Programming Interface.

The source code file is copyright 2010, 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
+/* t_mount.c
+   Demonstrate the use of mount(2) to create a mount point.
+   Usage: as described in usageError()
+   Examples:
+        t_mount -t ext3 /dev/sda12 /testfs
+        t_mount -t ext2 -f r -o nogrpid /dev/sda9 /mydir ext2
+                (The "r" for flags specifies that the file system
+                is to be mounted read-only.)
+   This program is Linux-specific.
 #include <sys/mount.h>
 #include "tlpi_hdr.h"
+#ifndef MS_DIRSYNC      /* May not be defined in older glibc headers */
+#define MS_DIRSYNC 128
+#ifndef MS_BIND         /* May not be defined in older glibc headers */
+#define MS_BIND 4096
+#ifndef MS_MOVE         /* May not be defined in older glibc headers */
+#define MS_MOVE 8192
+#ifndef MS_REC          /* May not be defined in older glibc headers */
+#define MS_REC 16384
+#ifndef MS_UNBINDABLE   /* May not be defined in older glibc headers */
+#define MS_UNBINDABLE (1<<17) /* change to unbindable */
+#ifndef MS_PRIVATE      /* May not be defined in older glibc headers */
+#define MS_PRIVATE (1<<18) /* change to private */
+#ifndef MS_SLAVE        /* May not be defined in older glibc headers */
+#define MS_SLAVE (1<<19) /* change to slave */
+#ifndef MS_SHARED       /* May not be defined in older glibc headers */
+#define MS_SHARED (1<<20) /* change to shared */
+#ifndef MS_LAZYTIME
+#define MS_LAZYTIME     (1<<25)
 static void
 usageError(const char *progName, const char *msg)
     if (msg != NULL)
         fprintf(stderr, "%s", msg);
     fprintf(stderr, "Usage: %s [options] source target\n\n", progName);
     fprintf(stderr, "Available options:\n");
 #define fpe(str) fprintf(stderr, "    " str)    /* Shorter! */
     fpe("-t fstype        [e.g., 'ext2' or 'reiserfs']\n");
     fpe("-o data          [file system-dependent options,\n");
     fpe("                 e.g., 'bsdgroups' for ext2]\n");
     fpe("-f mountflags    can include any of:\n");
 #define fpe2(str) fprintf(stderr, "            " str)
     fpe2("b - MS_BIND         create a bind mount\n");
     fpe2("d - MS_DIRSYNC      synchronous directory updates\n");
     fpe2("l - MS_MANDLOCK     permit mandatory locking\n");
+    fpe2("L - MS_LAZYATIME    lazy atime updates\n");
     fpe2("m - MS_MOVE         atomically move subtree\n");
     fpe2("A - MS_NOATIME      don't update atime (last access time)\n");
     fpe2("V - MS_NODEV        don't permit device access\n");
     fpe2("D - MS_NODIRATIME   don't update atime on directories\n");
     fpe2("E - MS_NOEXEC       don't allow executables\n");
     fpe2("S - MS_NOSUID       disable set-user/group-ID programs\n");
+    fpe2("p - MS_PRIVATE      mark as private\n");
     fpe2("r - MS_RDONLY       read-only mount\n");
     fpe2("c - MS_REC          recursive mount\n");
+    fpe2("T - MS_RELATIME     relative atime updates\n");
     fpe2("R - MS_REMOUNT      remount\n");
+    fpe2("h - MS_SHARED       mark as shared\n");
+    fpe2("v - MS_SLAVE        mark as slave\n");
     fpe2("s - MS_SYNCHRONOUS  make writes synchronous\n");
+    fpe2("u - MS_UNBINDABLE   mark as unbindable\n");
 main(int argc, char *argv[])
     unsigned long flags;
     char *data, *fstype;
     int j, opt;
     flags = 0;
     data = NULL;
     fstype = NULL;
     while ((opt = getopt(argc, argv, "o:t:f:")) != -1) {
         switch (opt) {
         case 'o':
             data = optarg;
         case 't':
             fstype = optarg;
         case 'f':
             for (j = 0; j < strlen(optarg); j++) {
+                /* In this version of the program we support more flags than
+                   in the version of the program shown in the book */
                 switch (optarg[j]) {
                 case 'b': flags |= MS_BIND;             break;
                 case 'd': flags |= MS_DIRSYNC;          break;
                 case 'l': flags |= MS_MANDLOCK;         break;
                 case 'm': flags |= MS_MOVE;             break;
                 case 'A': flags |= MS_NOATIME;          break;
                 case 'V': flags |= MS_NODEV;            break;
                 case 'D': flags |= MS_NODIRATIME;       break;
                 case 'E': flags |= MS_NOEXEC;           break;
                 case 'S': flags |= MS_NOSUID;           break;
+                case 'p': flags |= MS_PRIVATE;          break;
                 case 'r': flags |= MS_RDONLY;           break;
                 case 'c': flags |= MS_REC;              break;
+                case 'T': flags |= MS_RELATIME;         break;
                 case 'R': flags |= MS_REMOUNT;          break;
+                case 'h': flags |= MS_SHARED;           break;
+                case 'v': flags |= MS_SLAVE;            break;
                 case 's': flags |= MS_SYNCHRONOUS;      break;
+                case 'u': flags |= MS_UNBINDABLE;       break;
                 default:  usageError(argv[0], NULL);
             usageError(argv[0], NULL);
     if (argc != optind + 2)
         usageError(argv[0], "Wrong number of arguments\n");
     if (mount(argv[optind], argv[optind + 1], fstype, flags, data) == -1)

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.