234 lines
8.3 KiB
HTML
234 lines
8.3 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>mkfifo</title>
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<body bgcolor="white">
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<basefont size="3"> <a name="mkfifo"></a> <a name="tag_03_372"></a><!-- mkfifo -->
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<!--header start-->
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<center><font size="2">The Open Group Base Specifications Issue 6<br>
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IEEE Std 1003.1-2001<br>
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Copyright © 2001 The IEEE and The Open Group, All Rights reserved.</font></center>
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<!--header end-->
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<hr size="2" noshade>
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<h4><a name="tag_03_372_01"></a>NAME</h4>
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<blockquote>mkfifo - make a FIFO special file</blockquote>
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<h4><a name="tag_03_372_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/sys/stat.h.html">sys/stat.h</a>><br>
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<br>
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int mkfifo(const char *</tt><i>path</i><tt>, mode_t</tt> <i>mode</i><tt>);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_372_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>mkfifo</i>() function shall create a new FIFO special file named by the pathname pointed to by <i>path</i>. The file
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permission bits of the new FIFO shall be initialized from <i>mode</i>. The file permission bits of the <i>mode</i> argument shall
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be modified by the process' file creation mask.</p>
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<p>When bits in <i>mode</i> other than the file permission bits are set, the effect is implementation-defined.</p>
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<p>If <i>path</i> names a symbolic link, <i>mkfifo</i>() shall fail and set <i>errno</i> to [EEXIST].</p>
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<p>The FIFO's user ID shall be set to the process' effective user ID. The FIFO's group ID shall be set to the group ID of the
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parent directory or to the effective group ID of the process. Implementations shall provide a way to initialize the FIFO's group ID
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to the group ID of the parent directory. Implementations may, but need not, provide an implementation-defined way to initialize the
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FIFO's group ID to the effective group ID of the calling process.</p>
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<p>Upon successful completion, <i>mkfifo</i>() shall mark for update the <i>st_atime</i>, <i>st_ctime</i>, and <i>st_mtime</i>
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fields of the file. Also, the <i>st_ctime</i> and <i>st_mtime</i> fields of the directory that contains the new entry shall be
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marked for update.</p>
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</blockquote>
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<h4><a name="tag_03_372_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, 0 shall be returned. Otherwise, -1 shall be returned, no FIFO shall be created, and <i>errno</i>
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shall be set to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_372_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>mkfifo</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EACCES]</dt>
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<dd>A component of the path prefix denies search permission, or write permission is denied on the parent directory of the FIFO to
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be created.</dd>
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<dt>[EEXIST]</dt>
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<dd>The named file already exists.</dd>
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<dt>[ELOOP]</dt>
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<dd>A loop exists in symbolic links encountered during resolution of the <i>path</i> argument.</dd>
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<dt>[ENAMETOOLONG]</dt>
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<dd>
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The length of the <i>path</i> argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.</dd>
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<dt>[ENOENT]</dt>
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<dd>A component of the path prefix specified by <i>path</i> does not name an existing directory or <i>path</i> is an empty
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string.</dd>
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<dt>[ENOSPC]</dt>
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<dd>The directory that would contain the new file cannot be extended or the file system is out of file-allocation resources.</dd>
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<dt>[ENOTDIR]</dt>
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<dd>A component of the path prefix is not a directory.</dd>
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<dt>[EROFS]</dt>
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<dd>The named file resides on a read-only file system.</dd>
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</dl>
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<p>The <i>mkfifo</i>() function may fail if:</p>
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<dl compact>
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<dt>[ELOOP]</dt>
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<dd>More than {SYMLOOP_MAX} symbolic links were encountered during resolution of the <i>path</i> argument.</dd>
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<dt>[ENAMETOOLONG]</dt>
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<dd>
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As a result of encountering a symbolic link in resolution of the <i>path</i> argument, the length of the substituted pathname
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string exceeded {PATH_MAX}.</dd>
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</dl>
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</blockquote>
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<hr>
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<div class="box"><em>The following sections are informative.</em></div>
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<h4><a name="tag_03_372_06"></a>EXAMPLES</h4>
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<blockquote>
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<h5><a name="tag_03_372_06_01"></a>Creating a FIFO File</h5>
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<p>The following example shows how to create a FIFO file named <b>/home/cnd/mod_done</b>, with read/write permissions for owner,
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and with read permissions for group and others.</p>
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<pre>
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<tt>#include <sys/types.h>
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#include <sys/stat.h>
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<br>
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int status;
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...
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status = mkfifo("/home/cnd/mod_done", S_IWUSR | S_IRUSR |
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S_IRGRP | S_IROTH);
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_03_372_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_372_08"></a>RATIONALE</h4>
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<blockquote>
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<p>The syntax of this function is intended to maintain compatibility with historical implementations of <a href=
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"../functions/mknod.html"><i>mknod</i>()</a>. The latter function was included in the 1984 /usr/group standard but only for use in
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creating FIFO special files. The <a href="../functions/mknod.html"><i>mknod</i>()</a> function was originally excluded from the
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POSIX.1-1988 standard as implementation-defined and replaced by <a href="../functions/mkdir.html"><i>mkdir</i>()</a> and
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<i>mkfifo</i>(). The <a href="../functions/mknod.html"><i>mknod</i>()</a> function is now included for alignment with the Single
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UNIX Specification.</p>
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<p>The POSIX.1-1990 standard required that the group ID of a newly created FIFO be set to the group ID of its parent directory or
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to the effective group ID of the creating process. FIPS 151-2 required that implementations provide a way to have the group ID be
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set to the group ID of the containing directory, but did not prohibit implementations also supporting a way to set the group ID to
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the effective group ID of the creating process. Conforming applications should not assume which group ID will be used. If it
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matters, an application can use <a href="../functions/chown.html"><i>chown</i>()</a> to set the group ID after the FIFO is created,
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or determine under what conditions the implementation will set the desired group ID.</p>
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</blockquote>
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<h4><a name="tag_03_372_09"></a>FUTURE DIRECTIONS</h4>
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<blockquote>
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<p>None.</p>
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</blockquote>
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<h4><a name="tag_03_372_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="umask.html"><i>umask</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href=
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"../basedefs/sys/stat.h.html"><i><sys/stat.h></i></a>, <a href=
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"../basedefs/sys/types.h.html"><i><sys/types.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_372_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 3. Included for alignment with the POSIX.1-1988 standard.</p>
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</blockquote>
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<h4><a name="tag_03_372_12"></a>Issue 6</h4>
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<blockquote>
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<p>In the SYNOPSIS, the optional include of the <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> header is
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removed.</p>
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<p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p>
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<ul>
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<li>
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<p>The requirement to include <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> has been removed. Although <a
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href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> was required for conforming implementations of previous POSIX
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specifications, it was not required for UNIX applications.</p>
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</li>
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<li>
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<p>The [ELOOP] mandatory error condition is added.</p>
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</li>
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<li>
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<p>A second [ENAMETOOLONG] is added as an optional error condition.</p>
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</li>
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</ul>
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<p>The following changes were made to align with the IEEE P1003.1a draft standard:</p>
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<ul>
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<li>
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<p>The [ELOOP] optional error condition is added.</p>
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</li>
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</ul>
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</blockquote>
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<div class="box"><em>End of informative text.</em></div>
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<hr>
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<hr size="2" noshade>
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<center><font size="2"><!--footer start-->
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UNIX ® is a registered Trademark of The Open Group.<br>
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POSIX ® is a registered Trademark of The IEEE.<br>
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[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href=
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"../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>
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]</font></center>
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