240 lines
9.4 KiB
HTML
240 lines
9.4 KiB
HTML
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<title>getgrgid</title>
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<basefont size="3"> <a name="getgrgid"></a> <a name="tag_03_222"></a><!-- getgrgid -->
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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_222_01"></a>NAME</h4>
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<blockquote>getgrgid, getgrgid_r - get group database entry for a group ID</blockquote>
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<h4><a name="tag_03_222_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/grp.h.html">grp.h</a>><br>
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<br>
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struct group *getgrgid(gid_t</tt> <i>gid</i><tt>);<br>
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</tt></code></p>
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<div class="box"><code><tt><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt=
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"[Option Start]" border="0"> int getgrgid_r(gid_t</tt> <i>gid</i><tt>, struct group *</tt><i>grp</i><tt>, char
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*</tt><i>buffer</i><tt>,<br>
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size_t</tt> <i>bufsize</i><tt>, struct group **</tt><i>result</i><tt>); <img src=
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"../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div>
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<tt><br>
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</tt></blockquote>
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<h4><a name="tag_03_222_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>getgrgid</i>() function shall search the group database for an entry with a matching <i>gid</i>.</p>
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<p>The <i>getgrgid</i>() function need not be reentrant. A function that is not required to be reentrant is not required to be
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thread-safe.</p>
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<p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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The <i>getgrgid_r</i>() function shall update the <b>group</b> structure pointed to by <i>grp</i> and store a pointer to that
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structure at the location pointed to by <i>result</i>. The structure shall contain an entry from the group database with a matching
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<i>gid</i>. Storage referenced by the group structure is allocated from the memory provided with the <i>buffer</i> parameter, which
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is <i>bufsize</i> bytes in size. The maximum size needed for this buffer can be determined with the {_SC_GETGR_R_SIZE_MAX} <a href=
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"../functions/sysconf.html"><i>sysconf</i>()</a> parameter. A NULL pointer shall be returned at the location pointed to by
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<i>result</i> on error or if the requested entry is not found. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_222_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, <i>getgrgid</i>() shall return a pointer to a <b>struct group</b> with the structure defined in <a
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href="../basedefs/grp.h.html"><i><grp.h></i></a> with a matching entry if one is found. The <i>getgrgid</i>() function shall
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return a null pointer if either the requested entry was not found, or an error occurred. On error, <i>errno</i> shall be set to
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indicate the error.</p>
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<p>The return value may point to a static area which is overwritten by a subsequent call to <a href=
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"../functions/getgrent.html"><i>getgrent</i>()</a>, <i>getgrgid</i>(), or <a href=
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"../functions/getgrnam.html"><i>getgrnam</i>()</a>.</p>
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<p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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If successful, the <i>getgrgid_r</i>() function shall return zero; otherwise, an error number shall be returned to indicate the
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error. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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</blockquote>
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<h4><a name="tag_03_222_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>getgrgid</i>() and <i>getgrgid_r</i>() functions may fail if:</p>
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<dl compact>
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<dt>[EIO]</dt>
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<dd>An I/O error has occurred.</dd>
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<dt>[EINTR]</dt>
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<dd>A signal was caught during <i>getgrgid</i>().</dd>
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<dt>[EMFILE]</dt>
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<dd>{OPEN_MAX} file descriptors are currently open in the calling process.</dd>
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<dt>[ENFILE]</dt>
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<dd>The maximum allowable number of files is currently open in the system.</dd>
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</dl>
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<p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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The <i>getgrgid_r</i>() function may fail if: <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p>
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<dl compact>
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<dt>[ERANGE]</dt>
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<dd><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">
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Insufficient storage was supplied via <i>buffer</i> and <i>bufsize</i> to contain the data to be referenced by the resulting
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<b>group</b> structure. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></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_222_06"></a>EXAMPLES</h4>
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<blockquote>
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<h5><a name="tag_03_222_06_01"></a>Finding an Entry in the Group Database</h5>
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<p>The following example uses <i>getgrgid</i>() to search the group database for a group ID that was previously stored in a
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<b>stat</b> structure, then prints out the group name if it is found. If the group is not found, the program prints the numeric
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value of the group for the entry.</p>
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<pre>
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<tt>#include <sys/types.h>
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#include <grp.h>
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#include <stdio.h>
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...
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struct stat statbuf;
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struct group *grp;
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...
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if ((grp = getgrgid(statbuf.st_gid)) != NULL)
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printf(" %-8.8s", grp->gr_name);
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else
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printf(" %-8d", statbuf.st_gid);
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...
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_03_222_07"></a>APPLICATION USAGE</h4>
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<blockquote>
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<p>Applications wishing to check for error situations should set <i>errno</i> to 0 before calling <i>getgrgid</i>(). If
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<i>errno</i> is set on return, an error occurred.</p>
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<p>The <i>getgrgid_r</i>() function is thread-safe and shall return values in a user-supplied buffer instead of possibly using a
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static data area that may be overwritten by each call.</p>
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</blockquote>
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<h4><a name="tag_03_222_08"></a>RATIONALE</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_222_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_222_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="endgrent.html"><i>endgrent</i>()</a> , <a href="getgrnam.html"><i>getgrnam</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/grp.h.html"><i><grp.h></i></a>, <a href=
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"../basedefs/limits.h.html"><i><limits.h></i></a>, <a href="../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_222_11"></a>CHANGE HISTORY</h4>
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<blockquote>
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<p>First released in Issue 1. Derived from System V Release 2.0.</p>
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</blockquote>
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<h4><a name="tag_03_222_12"></a>Issue 5</h4>
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<blockquote>
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<p>Normative text previously in the APPLICATION USAGE section is moved to the RETURN VALUE section.</p>
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<p>The <i>getgrgid_r</i>() function is included for alignment with the POSIX Threads Extension.</p>
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<p>A note indicating that the <i>getgrgid</i>() function need not be reentrant is added to the DESCRIPTION.</p>
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</blockquote>
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<h4><a name="tag_03_222_13"></a>Issue 6</h4>
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<blockquote>
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<p>The <i>getgrgid_r</i>() function is marked as part of the Thread-Safe Functions option.</p>
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<p>The Open Group Corrigendum U028/3 is applied, correcting text in the DESCRIPTION describing matching the <i>gid</i>.</p>
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<p>In the DESCRIPTION, the note about reentrancy is expanded to cover thread-safety.</p>
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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>In the RETURN VALUE section, the requirement to set <i>errno</i> on error is added.</p>
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</li>
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<li>
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<p>The [EIO], [EINTR], [EMFILE], and [ENFILE] optional error conditions are added.</p>
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</li>
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</ul>
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<p>The APPLICATION USAGE section is updated to include a note on the thread-safe function and its avoidance of possibly using a
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static data area.</p>
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<p>IEEE PASC Interpretation 1003.1 #116 is applied, changing the description of the size of the buffer from <i>bufsize</i>
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characters to bytes.</p>
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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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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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