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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2004 IEEE and The Open Group, All Rights Reserved --><title>getgrgid</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="getgrgid"></a> <a name="tag_03_222"></a><!-- getgrgid --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2004 Edition<br>Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_222_01"></a>NAME</h4><blockquote>getgrgid, getgrgid_r - get group database entry for a group ID</blockquote><h4><a name="tag_03_222_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/grp.h.html">grp.h</a>><br><br> struct group *getgrgid(gid_t</tt> <i>gid</i><tt>);<br></tt></code></p><div class="box"><code><tt><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0"> int getgrgid_r(gid_t</tt> <i>gid</i><tt>, struct group *</tt><i>grp</i><tt>, char*</tt><i>buffer</i><tt>,<br> size_t</tt> <i>bufsize</i><tt>, struct group **</tt><i>result</i><tt>); <img src="../images/opt-end.gif" alt="[Option End]" border="0"></tt></code></div><tt><br></tt></blockquote><h4><a name="tag_03_222_03"></a>DESCRIPTION</h4><blockquote><p>The <i>getgrgid</i>() function shall search the group database for an entry with a matching <i>gid</i>.</p><p>The <i>getgrgid</i>() function need not be reentrant. A function that is not required to be reentrant is not required to bethread-safe.</p><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The <i>getgrgid_r</i>() function shall update the <b>group</b> structure pointed to by <i>grp</i> and store a pointer to thatstructure at the location pointed to by <i>result</i>. The structure shall contain an entry from the group database with a matching<i>gid</i>. Storage referenced by the group structure is allocated from the memory provided with the <i>buffer</i> parameter, whichis <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="../functions/sysconf.html"><i>sysconf</i>()</a> parameter. A NULL pointer shall be returned at the location pointed to by<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></blockquote><h4><a name="tag_03_222_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>getgrgid</i>() shall return a pointer to a <b>struct group</b> with the structure defined in <ahref="../basedefs/grp.h.html"><i><grp.h></i></a> with a matching entry if one is found. The <i>getgrgid</i>() function shallreturn a null pointer if either the requested entry was not found, or an error occurred. On error, <i>errno</i> shall be set toindicate the error.</p><p>The return value may point to a static area which is overwritten by a subsequent call to <a href="../functions/getgrent.html"><i>getgrent</i>()</a>, <i>getgrgid</i>(), or <a href="../functions/getgrnam.html"><i>getgrnam</i>()</a>.</p><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">If successful, the <i>getgrgid_r</i>() function shall return zero; otherwise, an error number shall be returned to indicate theerror. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p></blockquote><h4><a name="tag_03_222_05"></a>ERRORS</h4><blockquote><p>The <i>getgrgid</i>() and <i>getgrgid_r</i>() functions may fail if:</p><dl compact><dt>[EIO]</dt><dd>An I/O error has occurred.</dd><dt>[EINTR]</dt><dd>A signal was caught during <i>getgrgid</i>().</dd><dt>[EMFILE]</dt><dd>{OPEN_MAX} file descriptors are currently open in the calling process.</dd><dt>[ENFILE]</dt><dd>The maximum allowable number of files is currently open in the system.</dd></dl><p><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">The <i>getgrgid_r</i>() function may fail if: <img src="../images/opt-end.gif" alt="[Option End]" border="0"></p><dl compact><dt>[ERANGE]</dt><dd><sup>[<a href="javascript:open_code('TSF')">TSF</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Insufficient storage was supplied via <i>buffer</i> and <i>bufsize</i> to contain the data to be referenced by the resulting<b>group</b> structure. <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_222_06"></a>EXAMPLES</h4><blockquote><h5><a name="tag_03_222_06_01"></a>Finding an Entry in the Group Database</h5><p>The following example uses <i>getgrgid</i>() to search the group database for a group ID that was previously stored in a<b>stat</b> structure, then prints out the group name if it is found. If the group is not found, the program prints the numericvalue of the group for the entry.</p><pre><tt>#include <sys/types.h>#include <grp.h>#include <stdio.h>...struct stat statbuf;struct group *grp;...if ((grp = getgrgid(statbuf.st_gid)) != NULL) printf(" %-8.8s", grp->gr_name);else printf(" %-8d", statbuf.st_gid);...</tt></pre></blockquote><h4><a name="tag_03_222_07"></a>APPLICATION USAGE</h4><blockquote><p>Applications wishing to check for error situations should set <i>errno</i> to 0 before calling <i>getgrgid</i>(). If<i>errno</i> is set on return, an error occurred.</p><p>The <i>getgrgid_r</i>() function is thread-safe and shall return values in a user-supplied buffer instead of possibly using astatic data area that may be overwritten by each call.</p></blockquote><h4><a name="tag_03_222_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_222_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_222_10"></a>SEE ALSO</h4><blockquote><p><a href="endgrent.html"><i>endgrent</i>()</a>, <a href="getgrnam.html"><i>getgrnam</i>()</a>, the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/grp.h.html"><i><grp.h></i></a>, <a href="../basedefs/limits.h.html"><i><limits.h></i></a>, <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a></p></blockquote><h4><a name="tag_03_222_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 1. Derived from System V Release 2.0.</p></blockquote><h4><a name="tag_03_222_12"></a>Issue 5</h4><blockquote><p>Normative text previously in the APPLICATION USAGE section is moved to the RETURN VALUE section.</p><p>The <i>getgrgid_r</i>() function is included for alignment with the POSIX Threads Extension.</p><p>A note indicating that the <i>getgrgid</i>() function need not be reentrant is added to the DESCRIPTION.</p></blockquote><h4><a name="tag_03_222_13"></a>Issue 6</h4><blockquote><p>The <i>getgrgid_r</i>() function is marked as part of the Thread-Safe Functions option.</p><p>The Open Group Corrigendum U028/3 is applied, correcting text in the DESCRIPTION describing matching the <i>gid</i>.</p><p>In the DESCRIPTION, the note about reentrancy is expanded to cover thread-safety.</p><p>In the SYNOPSIS, the optional include of the <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> header isremoved.</p><p>The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:</p><ul><li><p>The requirement to include <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> has been removed. Although <ahref="../basedefs/sys/types.h.html"><i><sys/types.h></i></a> was required for conforming implementations of previous POSIXspecifications, it was not required for UNIX applications.</p></li><li><p>In the RETURN VALUE section, the requirement to set <i>errno</i> on error is added.</p></li><li><p>The [EIO], [EINTR], [EMFILE], and [ENFILE] optional error conditions are added.</p></li></ul><p>The APPLICATION USAGE section is updated to include a note on the thread-safe function and its avoidance of possibly using astatic data area.</p><p>IEEE PASC Interpretation 1003.1 #116 is applied, changing the description of the size of the buffer from <i>bufsize</i>characters to bytes.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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