| <html lang="en"> |
| <head> |
| <title>Reading Persona - The GNU C Library</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="The GNU C Library"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Users-and-Groups.html#Users-and-Groups" title="Users and Groups"> |
| <link rel="prev" href="How-Change-Persona.html#How-Change-Persona" title="How Change Persona"> |
| <link rel="next" href="Setting-User-ID.html#Setting-User-ID" title="Setting User ID"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU C library. |
| |
| This is Edition 0.12, last updated 2007-10-27, |
| of `The GNU C Library Reference Manual', for version |
| 2.8 (Sourcery G++ Lite 2011.03-41). |
| |
| Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, |
| 2003, 2007, 2008, 2010 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 or |
| any later version published by the Free Software Foundation; with the |
| Invariant Sections being ``Free Software Needs Free Documentation'' |
| and ``GNU Lesser General Public License'', the Front-Cover texts being |
| ``A GNU Manual'', and with the Back-Cover Texts as in (a) below. A |
| copy of the license is included in the section entitled "GNU Free |
| Documentation License". |
| |
| (a) The FSF's Back-Cover Text is: ``You have the freedom to |
| copy and modify this GNU manual. Buying copies from the FSF |
| supports it in developing GNU and promoting software freedom.''--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Reading-Persona"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Setting-User-ID.html#Setting-User-ID">Setting User ID</a>, |
| Previous: <a rel="previous" accesskey="p" href="How-Change-Persona.html#How-Change-Persona">How Change Persona</a>, |
| Up: <a rel="up" accesskey="u" href="Users-and-Groups.html#Users-and-Groups">Users and Groups</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">29.5 Reading the Persona of a Process</h3> |
| |
| <p>Here are detailed descriptions of the functions for reading the user and |
| group IDs of a process, both real and effective. To use these |
| facilities, you must include the header files <samp><span class="file">sys/types.h</span></samp> and |
| <samp><span class="file">unistd.h</span></samp>. |
| <a name="index-unistd_002eh-3305"></a><a name="index-sys_002ftypes_002eh-3306"></a> |
| <!-- sys/types.h --> |
| <!-- POSIX.1 --> |
| |
| <div class="defun"> |
| — Data Type: <b>uid_t</b><var><a name="index-uid_005ft-3307"></a></var><br> |
| <blockquote><p>This is an integer data type used to represent user IDs. In the GNU |
| library, this is an alias for <code>unsigned int</code>. |
| </p></blockquote></div> |
| |
| <!-- sys/types.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Data Type: <b>gid_t</b><var><a name="index-gid_005ft-3308"></a></var><br> |
| <blockquote><p>This is an integer data type used to represent group IDs. In the GNU |
| library, this is an alias for <code>unsigned int</code>. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: uid_t <b>getuid</b> (<var>void</var>)<var><a name="index-getuid-3309"></a></var><br> |
| <blockquote><p>The <code>getuid</code> function returns the real user ID of the process. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: gid_t <b>getgid</b> (<var>void</var>)<var><a name="index-getgid-3310"></a></var><br> |
| <blockquote><p>The <code>getgid</code> function returns the real group ID of the process. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: uid_t <b>geteuid</b> (<var>void</var>)<var><a name="index-geteuid-3311"></a></var><br> |
| <blockquote><p>The <code>geteuid</code> function returns the effective user ID of the process. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: gid_t <b>getegid</b> (<var>void</var>)<var><a name="index-getegid-3312"></a></var><br> |
| <blockquote><p>The <code>getegid</code> function returns the effective group ID of the process. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: int <b>getgroups</b> (<var>int count, gid_t *groups</var>)<var><a name="index-getgroups-3313"></a></var><br> |
| <blockquote><p>The <code>getgroups</code> function is used to inquire about the supplementary |
| group IDs of the process. Up to <var>count</var> of these group IDs are |
| stored in the array <var>groups</var>; the return value from the function is |
| the number of group IDs actually stored. If <var>count</var> is smaller than |
| the total number of supplementary group IDs, then <code>getgroups</code> |
| returns a value of <code>-1</code> and <code>errno</code> is set to <code>EINVAL</code>. |
| |
| <p>If <var>count</var> is zero, then <code>getgroups</code> just returns the total |
| number of supplementary group IDs. On systems that do not support |
| supplementary groups, this will always be zero. |
| |
| <p>Here's how to use <code>getgroups</code> to read all the supplementary group |
| IDs: |
| |
| <pre class="smallexample"> gid_t * |
| read_all_groups (void) |
| { |
| int ngroups = getgroups (0, NULL); |
| gid_t *groups |
| = (gid_t *) xmalloc (ngroups * sizeof (gid_t)); |
| int val = getgroups (ngroups, groups); |
| if (val < 0) |
| { |
| free (groups); |
| return NULL; |
| } |
| return groups; |
| } |
| </pre> |
| </blockquote></div> |
| |
| </body></html> |
| |
