189 lines
6.8 KiB
HTML
189 lines
6.8 KiB
HTML
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<!-- Copyright (c) 2001 The Open Group, All Rights Reserved -->
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<title>getgroups</title>
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<body bgcolor="white">
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<basefont size="3"> <a name="getgroups"></a> <a name="tag_03_224"></a><!-- getgroups -->
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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_224_01"></a>NAME</h4>
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<blockquote>getgroups - get supplementary group IDs</blockquote>
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<h4><a name="tag_03_224_02"></a>SYNOPSIS</h4>
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<blockquote class="synopsis">
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<p><code><tt>#include <<a href="../basedefs/unistd.h.html">unistd.h</a>><br>
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<br>
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int getgroups(int</tt> <i>gidsetsize</i><tt>, gid_t</tt> <i>grouplist</i><tt>[]);<br>
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</tt></code></p>
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</blockquote>
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<h4><a name="tag_03_224_03"></a>DESCRIPTION</h4>
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<blockquote>
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<p>The <i>getgroups</i>() function shall fill in the array <i>grouplist</i> with the current supplementary group IDs of the calling
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process. It is implementation-defined whether <i>getgroups</i>() also returns the effective group ID in the <i>grouplist</i>
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array.</p>
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<p>The <i>gidsetsize</i> argument specifies the number of elements in the array <i>grouplist</i>. The actual number of group IDs
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stored in the array shall be returned. The values of array entries with indices greater than or equal to the value returned are
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undefined.</p>
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<p>If <i>gidsetsize</i> is 0, <i>getgroups</i>() shall return the number of group IDs that it would otherwise return without
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modifying the array pointed to by <i>grouplist</i>.</p>
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<p>If the effective group ID of the process is returned with the supplementary group IDs, the value returned shall always be
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greater than or equal to one and less than or equal to the value of {NGROUPS_MAX}+1.</p>
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</blockquote>
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<h4><a name="tag_03_224_04"></a>RETURN VALUE</h4>
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<blockquote>
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<p>Upon successful completion, the number of supplementary group IDs shall be returned. A return value of -1 indicates failure and
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<i>errno</i> shall be set to indicate the error.</p>
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</blockquote>
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<h4><a name="tag_03_224_05"></a>ERRORS</h4>
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<blockquote>
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<p>The <i>getgroups</i>() function shall fail if:</p>
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<dl compact>
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<dt>[EINVAL]</dt>
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<dd>The <i>gidsetsize</i> argument is non-zero and less than the number of group IDs that would have been returned.</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_224_06"></a>EXAMPLES</h4>
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<blockquote>
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<h5><a name="tag_03_224_06_01"></a>Getting the Supplementary Group IDs of the Calling Process</h5>
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<p>The following example places the current supplementary group IDs of the calling process into the <i>group</i> array.</p>
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<pre>
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<tt>#include <sys/types.h>
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#include <unistd.h>
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...
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gid_t *group;
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int nogroups;
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long ngroups_max;
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<br>
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ngroups_max = sysconf(_SC_NGROUPS_MAX) + 1;
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group = (gid_t *)malloc(ngroups_max *sizeof(gid_t));
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<br>
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ngroups = getgroups(ngroups_max, group);
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</tt>
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</pre>
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</blockquote>
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<h4><a name="tag_03_224_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_224_08"></a>RATIONALE</h4>
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<blockquote>
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<p>The related function <i>setgroups</i>() is a privileged operation and therefore is not covered by this volume of
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IEEE Std 1003.1-2001.</p>
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<p>As implied by the definition of supplementary groups, the effective group ID may appear in the array returned by
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<i>getgroups</i>() or it may be returned only by <a href="../functions/getegid.html"><i>getegid</i>()</a>. Duplication may exist,
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but the application needs to call <a href="../functions/getegid.html"><i>getegid</i>()</a> to be sure of getting all of the
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information. Various implementation variations and administrative sequences cause the set of groups appearing in the result of
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<i>getgroups</i>() to vary in order and as to whether the effective group ID is included, even when the set of groups is the same
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(in the mathematical sense of "set"). (The history of a process and its parents could affect the details of the result.)</p>
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<p>Application writers should note that {NGROUPS_MAX} is not necessarily a constant on all implementations.</p>
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</blockquote>
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<h4><a name="tag_03_224_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_224_10"></a>SEE ALSO</h4>
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<blockquote>
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<p><a href="getegid.html"><i>getegid</i>()</a> , <a href="setgid.html"><i>setgid</i>()</a> , the Base Definitions volume of
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IEEE Std 1003.1-2001, <a href="../basedefs/sys/types.h.html"><i><sys/types.h></i></a>, <a href=
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"../basedefs/unistd.h.html"><i><unistd.h></i></a></p>
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</blockquote>
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<h4><a name="tag_03_224_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_224_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 DESCRIPTION.</p>
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</blockquote>
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<h4><a name="tag_03_224_13"></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>A return value of 0 is not permitted, because {NGROUPS_MAX} cannot be 0. This is a FIPS requirement.</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>Explanation added that the effective group ID may be included in the supplementary group list.</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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