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| <h5 class="subsubsection">30.3.1.1 The <samp><span class="file">fstab</span></samp> file</h5> |
| |
| <p>The internal representation for entries of the file is <code>struct fstab</code><!-- /@w -->, defined in <samp><span class="file">fstab.h</span></samp>. |
| |
| <!-- fstab.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Data Type: <b>struct fstab</b><var><a name="index-struct-fstab-3464"></a></var><br> |
| <blockquote><p>This structure is used with the <code>getfsent</code>, <code>getfsspec</code>, and |
| <code>getfsfile</code> functions. |
| |
| <dl> |
| <dt><code>char *fs_spec</code><dd>This element describes the device from which the filesystem is mounted. |
| Normally this is the name of a special device, such as a hard disk |
| partition, but it could also be a more or less generic string. For |
| <dfn>NFS</dfn> it would be a hostname and directory name combination. |
| |
| <p>Even though the element is not declared <code>const</code> it shouldn't be |
| modified. The missing <code>const</code> has historic reasons, since this |
| function predates ISO C<!-- /@w -->. The same is true for the other string |
| elements of this structure. |
| |
| <br><dt><code>char *fs_file</code><dd>This describes the mount point on the local system. I.e., accessing any |
| file in this filesystem has implicitly or explicitly this string as a |
| prefix. |
| |
| <br><dt><code>char *fs_vfstype</code><dd>This is the type of the filesystem. Depending on what the underlying |
| kernel understands it can be any string. |
| |
| <br><dt><code>char *fs_mntops</code><dd>This is a string containing options passed to the kernel with the |
| <code>mount</code> call. Again, this can be almost anything. There can be |
| more than one option, separated from the others by a comma. Each option |
| consists of a name and an optional value part, introduced by an <code>=</code> |
| character. |
| |
| <p>If the value of this element must be processed it should ideally be done |
| using the <code>getsubopt</code> function; see <a href="Suboptions.html#Suboptions">Suboptions</a>. |
| |
| <br><dt><code>const char *fs_type</code><dd>This name is poorly chosen. This element points to a string (possibly |
| in the <code>fs_mntops</code> string) which describes the modes with which the |
| filesystem is mounted. <samp><span class="file">fstab</span></samp> defines five macros to describe the |
| possible values: |
| |
| <dl> |
| <dt><code>FSTAB_RW</code><a name="index-FSTAB_005fRW-3465"></a><dd>The filesystems gets mounted with read and write enabled. |
| <br><dt><code>FSTAB_RQ</code><a name="index-FSTAB_005fRQ-3466"></a><dd>The filesystems gets mounted with read and write enabled. Write access |
| is restricted by quotas. |
| <br><dt><code>FSTAB_RO</code><a name="index-FSTAB_005fRO-3467"></a><dd>The filesystem gets mounted read-only. |
| <br><dt><code>FSTAB_SW</code><a name="index-FSTAB_005fSW-3468"></a><dd>This is not a real filesystem, it is a swap device. |
| <br><dt><code>FSTAB_XX</code><a name="index-FSTAB_005fXX-3469"></a><dd>This entry from the <samp><span class="file">fstab</span></samp> file is totally ignored. |
| </dl> |
| |
| <p>Testing for equality with these value must happen using <code>strcmp</code> |
| since these are all strings. Comparing the pointer will probably always |
| fail. |
| |
| <br><dt><code>int fs_freq</code><dd>This element describes the dump frequency in days. |
| |
| <br><dt><code>int fs_passno</code><dd>This element describes the pass number on parallel dumps. It is closely |
| related to the <code>dump</code> utility used on Unix systems. |
| </dl> |
| </p></blockquote></div> |
| |
| <p>To read the entire content of the of the <samp><span class="file">fstab</span></samp> file the GNU libc |
| contains a set of three functions which are designed in the usual way. |
| |
| <!-- fstab.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: int <b>setfsent</b> (<var>void</var>)<var><a name="index-setfsent-3470"></a></var><br> |
| <blockquote><p>This function makes sure that the internal read pointer for the |
| <samp><span class="file">fstab</span></samp> file is at the beginning of the file. This is done by |
| either opening the file or resetting the read pointer. |
| |
| <p>Since the file handle is internal to the libc this function is not |
| thread-safe. |
| |
| <p>This function returns a non-zero value if the operation was successful |
| and the <code>getfs*</code> functions can be used to read the entries of the |
| file. |
| </p></blockquote></div> |
| |
| <!-- fstab.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: void <b>endfsent</b> (<var>void</var>)<var><a name="index-endfsent-3471"></a></var><br> |
| <blockquote><p>This function makes sure that all resources acquired by a prior call to |
| <code>setfsent</code> (explicitly or implicitly by calling <code>getfsent</code>) are |
| freed. |
| </p></blockquote></div> |
| |
| <!-- fstab.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: struct fstab * <b>getfsent</b> (<var>void</var>)<var><a name="index-getfsent-3472"></a></var><br> |
| <blockquote><p>This function returns the next entry of the <samp><span class="file">fstab</span></samp> file. If this |
| is the first call to any of the functions handling <samp><span class="file">fstab</span></samp> since |
| program start or the last call of <code>endfsent</code>, the file will be |
| opened. |
| |
| <p>The function returns a pointer to a variable of type <code>struct |
| fstab</code>. This variable is shared by all threads and therefore this |
| function is not thread-safe. If an error occurred <code>getfsent</code> |
| returns a <code>NULL</code> pointer. |
| </p></blockquote></div> |
| |
| <!-- fstab.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: struct fstab * <b>getfsspec</b> (<var>const char *name</var>)<var><a name="index-getfsspec-3473"></a></var><br> |
| <blockquote><p>This function returns the next entry of the <samp><span class="file">fstab</span></samp> file which has |
| a string equal to <var>name</var> pointed to by the <code>fs_spec</code> element. |
| Since there is normally exactly one entry for each special device it |
| makes no sense to call this function more than once for the same |
| argument. If this is the first call to any of the functions handling |
| <samp><span class="file">fstab</span></samp> since program start or the last call of <code>endfsent</code>, |
| the file will be opened. |
| |
| <p>The function returns a pointer to a variable of type <code>struct |
| fstab</code>. This variable is shared by all threads and therefore this |
| function is not thread-safe. If an error occurred <code>getfsent</code> |
| returns a <code>NULL</code> pointer. |
| </p></blockquote></div> |
| |
| <!-- fstab.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: struct fstab * <b>getfsfile</b> (<var>const char *name</var>)<var><a name="index-getfsfile-3474"></a></var><br> |
| <blockquote><p>This function returns the next entry of the <samp><span class="file">fstab</span></samp> file which has |
| a string equal to <var>name</var> pointed to by the <code>fs_file</code> element. |
| Since there is normally exactly one entry for each mount point it |
| makes no sense to call this function more than once for the same |
| argument. If this is the first call to any of the functions handling |
| <samp><span class="file">fstab</span></samp> since program start or the last call of <code>endfsent</code>, |
| the file will be opened. |
| |
| <p>The function returns a pointer to a variable of type <code>struct |
| fstab</code>. This variable is shared by all threads and therefore this |
| function is not thread-safe. If an error occurred <code>getfsent</code> |
| returns a <code>NULL</code> pointer. |
| </p></blockquote></div> |
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