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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>id</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="id"></a> <a name="tag_04_67"></a><!-- id --> <!--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_04_67_01"></a>NAME</h4><blockquote>id - return user identity</blockquote><h4><a name="tag_04_67_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>id</tt> <b>[</b><i>user</i><b>]</b><tt><br><br>id -G</tt><b>[</b><tt>-n</tt><b>] [</b><i>user</i><b>]</b><tt><br><br>id -g</tt><b>[</b><tt>-nr</tt><b>] [</b><i>user</i><b>]</b><tt><br><br>id -u</tt><b>[</b><tt>-nr</tt><b>] [</b><i>user</i><b>]</b><tt><br></tt></code></p></blockquote><h4><a name="tag_04_67_03"></a>DESCRIPTION</h4><blockquote><p>If no <i>user</i> operand is provided, the <i>id</i> utility shall write the user and group IDs and the corresponding user andgroup names of the invoking process to standard output. If the effective and real IDs do not match, both shall be written. Ifmultiple groups are supported by the underlying system (see the description of {NGROUPS_MAX} in the System Interfaces volume ofIEEE Std 1003.1-2001), the supplementary group affiliations of the invoking process shall also be written.</p><p>If a <i>user</i> operand is provided and the process has the appropriate privileges, the user and group IDs of the selected usershall be written. In this case, effective IDs shall be assumed to be identical to real IDs. If the selected user has more than oneallowable group membership listed in the group database, these shall be written in the same manner as the supplementary groupsdescribed in the preceding paragraph.</p></blockquote><h4><a name="tag_04_67_04"></a>OPTIONS</h4><blockquote><p>The <i>id</i> utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap12.html#tag_12_02">Section 12.2, Utility Syntax Guidelines</a>.</p><p>The following options shall be supported:</p><dl compact><dt><b>-G</b></dt><dd>Output all different group IDs (effective, real, and supplementary) only, using the format <tt>"%u\n"</tt>. If there is morethan one distinct group affiliation, output each such affiliation, using the format <tt>" %u"</tt>, before the<newline> is output.</dd><dt><b>-g</b></dt><dd>Output only the effective group ID, using the format <tt>"%u\n"</tt>.</dd><dt><b>-n</b></dt><dd>Output the name in the format <tt>"%s"</tt> instead of the numeric ID using the format <tt>"%u"</tt>.</dd><dt><b>-r</b></dt><dd>Output the real ID instead of the effective ID.</dd><dt><b>-u</b></dt><dd>Output only the effective user ID, using the format <tt>"%u\n"</tt>.</dd></dl></blockquote><h4><a name="tag_04_67_05"></a>OPERANDS</h4><blockquote><p>The following operand shall be supported:</p><dl compact><dt><i>user</i></dt><dd>The login name for which information is to be written.</dd></dl></blockquote><h4><a name="tag_04_67_06"></a>STDIN</h4><blockquote><p>Not used.</p></blockquote><h4><a name="tag_04_67_07"></a>INPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_67_08"></a>ENVIRONMENT VARIABLES</h4><blockquote><p>The following environment variables shall affect the execution of <i>id</i>:</p><dl compact><dt><i>LANG</i></dt><dd>Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume ofIEEE Std 1003.1-2001, <a href="../basedefs/xbd_chap08.html#tag_08_02">Section 8.2, Internationalization Variables</a> forthe precedence of internationalization variables used to determine the values of locale categories.)</dd><dt><i>LC_ALL</i></dt><dd>If set to a non-empty string value, override the values of all the other internationalization variables.</dd><dt><i>LC_CTYPE</i></dt><dd>Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte asopposed to multi-byte characters in arguments).</dd><dt><i>LC_MESSAGES</i></dt><dd>Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error andinformative messages written to standard output.</dd><dt><i>NLSPATH</i></dt><dd><sup>[<a href="javascript:open_code('XSI')">XSI</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">Determine the location of message catalogs for the processing of <i>LC_MESSAGES .</i> <img src="../images/opt-end.gif" alt="[Option End]" border="0"></dd></dl></blockquote><h4><a name="tag_04_67_09"></a>ASYNCHRONOUS EVENTS</h4><blockquote><p>Default.</p></blockquote><h4><a name="tag_04_67_10"></a>STDOUT</h4><blockquote><p>The following formats shall be used when the <i>LC_MESSAGES</i> locale category specifies the POSIX locale. In other locales,the strings <i>uid</i>, <i>gid</i>, <i>euid</i>, <i>egid</i>, and <i>groups</i> may be replaced with more appropriate stringscorresponding to the locale.</p><pre><tt>"uid=%u(%s) gid=%u(%s)\n", <</tt><i>real user ID</i><tt>>, <</tt><i>user-name</i><tt>>, <</tt><i>real group ID</i><tt>>, <</tt><i>group-name</i><tt>></tt></pre><p>If the effective and real user IDs do not match, the following shall be inserted immediately before the <tt>'\n'</tt> characterin the previous format:</p><pre><tt>" euid=%u(%s)"</tt></pre><p>with the following arguments added at the end of the argument list:</p><pre><tt><</tt><i>effective user ID</i><tt>>, <</tt><i>effective user-name</i><tt>></tt></pre><p>If the effective and real group IDs do not match, the following shall be inserted directly before the <tt>'\n'</tt> character inthe format string (and after any addition resulting from the effective and real user IDs not matching):</p><pre><tt>" egid=%u(%s)"</tt></pre><p>with the following arguments added at the end of the argument list:</p><pre><tt><</tt><i>effective group-ID</i><tt>>, <</tt><i>effective group name</i><tt>></tt></pre><p>If the process has supplementary group affiliations or the selected user is allowed to belong to multiple groups, the firstshall be added directly before the <newline> in the format string:</p><pre><tt>" groups=%u(%s)"</tt></pre><p>with the following arguments added at the end of the argument list:</p><pre><tt><</tt><i>supplementary group ID</i><tt>>, <</tt><i>supplementary group name</i><tt>></tt></pre><p>and the necessary number of the following added after that for any remaining supplementary group IDs:</p><pre><tt>",%u(%s)"</tt></pre><p>and the necessary number of the following arguments added at the end of the argument list:</p><pre><tt><</tt><i>supplementary group ID</i><tt>>, <</tt><i>supplementary group name</i><tt>></tt></pre><p>If any of the user ID, group ID, effective user ID, effective group ID, or supplementary/multiple group IDs cannot be mapped bythe system into printable user or group names, the corresponding <tt>"(%s)"</tt> and <i>name</i> argument shall be omitted from thecorresponding format string.</p><p>When any of the options are specified, the output format shall be as described in the OPTIONS section.</p></blockquote><h4><a name="tag_04_67_11"></a>STDERR</h4><blockquote><p>The standard error shall be used only for diagnostic messages.</p></blockquote><h4><a name="tag_04_67_12"></a>OUTPUT FILES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_67_13"></a>EXTENDED DESCRIPTION</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_67_14"></a>EXIT STATUS</h4><blockquote><p>The following exit values shall be returned:</p><dl compact><dt> 0</dt><dd>Successful completion.</dd><dt>>0</dt><dd>An error occurred.</dd></dl></blockquote><h4><a name="tag_04_67_15"></a>CONSEQUENCES OF ERRORS</h4><blockquote><p>Default.</p></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_04_67_16"></a>APPLICATION USAGE</h4><blockquote><p>Output produced by the <b>-G</b> option and by the default case could potentially produce very long lines on systems thatsupport large numbers of supplementary groups. (On systems with user and group IDs that are 32-bit integers and with group nameswith a maximum of 8 bytes per name, 93 supplementary groups plus distinct effective and real group and user IDs could theoreticallyoverflow the 2048-byte {LINE_MAX} text file line limit on the default output case. It would take about 186 supplementary groups tooverflow the 2048-byte barrier using <i>id</i> <b>-G</b>). This is not expected to be a problem in practice, but in cases where itis a concern, applications should consider using <a href="../utilities/fold.html"><i>fold</i></a> <b>-s</b> before postprocessingthe output of <i>id</i>.</p></blockquote><h4><a name="tag_04_67_17"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_67_18"></a>RATIONALE</h4><blockquote><p>The functionality provided by the 4 BSD <i>groups</i> utility can be simulated using:</p><pre><tt>id -Gn [ user ]</tt></pre><p>The 4 BSD command <i>groups</i> was considered, but it was not included because it did not provide the functionality of the<i>id</i> utility of the SVID. Also, it was thought that it would be easier to modify <i>id</i> to provide the additionalfunctionality necessary to systems with multiple groups than to invent another command.</p><p>The options <b>-u</b>, <b>-g</b>, <b>-n</b>, and <b>-r</b> were added to ease the use of <i>id</i> with shell commandssubstitution. Without these options it is necessary to use some preprocessor such as <a href="../utilities/sed.html"><i>sed</i></a>to select the desired piece of information. Since output such as that produced by:</p><pre><tt>id -u -n</tt></pre><p>is frequently wanted, it seemed desirable to add the options.</p></blockquote><h4><a name="tag_04_67_19"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_04_67_20"></a>SEE ALSO</h4><blockquote><p><a href="fold.html"><i>fold</i></a>, <a href="logname.html"><i>logname</i></a>, <a href="who.html"><i>who</i></a>, the SystemInterfaces volume of IEEE Std 1003.1-2001, <a href="../functions/getgid.html"><i>getgid</i>()</a>, <a href="../functions/getgroups.html"><i>getgroups</i>()</a>, <a href="../functions/getuid.html"><i>getuid</i>()</a></p></blockquote><h4><a name="tag_04_67_21"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 2.</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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