| <html lang="en"> |
| <head> |
| <title>Setting User ID - 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="Reading-Persona.html#Reading-Persona" title="Reading Persona"> |
| <link rel="next" href="Setting-Groups.html#Setting-Groups" title="Setting Groups"> |
| <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="Setting-User-ID"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Setting-Groups.html#Setting-Groups">Setting Groups</a>, |
| Previous: <a rel="previous" accesskey="p" href="Reading-Persona.html#Reading-Persona">Reading 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">29.6 Setting the User ID</h3> |
| |
| <p>This section describes the functions for altering the user ID (real |
| and/or effective) of a process. 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-3314"></a><a name="index-sys_002ftypes_002eh-3315"></a> |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| |
| <div class="defun"> |
| — Function: int <b>seteuid</b> (<var>uid_t neweuid</var>)<var><a name="index-seteuid-3316"></a></var><br> |
| <blockquote><p>This function sets the effective user ID of a process to <var>newuid</var>, |
| provided that the process is allowed to change its effective user ID. A |
| privileged process (effective user ID zero) can change its effective |
| user ID to any legal value. An unprivileged process with a file user ID |
| can change its effective user ID to its real user ID or to its file user |
| ID. Otherwise, a process may not change its effective user ID at all. |
| |
| <p>The <code>seteuid</code> function returns a value of <code>0</code> to indicate |
| successful completion, and a value of <code>-1</code> to indicate an error. |
| The following <code>errno</code> error conditions are defined for this |
| function: |
| |
| <dl> |
| <dt><code>EINVAL</code><dd>The value of the <var>newuid</var> argument is invalid. |
| |
| <br><dt><code>EPERM</code><dd>The process may not change to the specified ID. |
| </dl> |
| |
| <p>Older systems (those without the <code>_POSIX_SAVED_IDS</code> feature) do not |
| have this function. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- POSIX.1 --> |
| <div class="defun"> |
| — Function: int <b>setuid</b> (<var>uid_t newuid</var>)<var><a name="index-setuid-3317"></a></var><br> |
| <blockquote><p>If the calling process is privileged, this function sets both the real |
| and effective user ID of the process to <var>newuid</var>. It also deletes |
| the file user ID of the process, if any. <var>newuid</var> may be any |
| legal value. (Once this has been done, there is no way to recover the |
| old effective user ID.) |
| |
| <p>If the process is not privileged, and the system supports the |
| <code>_POSIX_SAVED_IDS</code> feature, then this function behaves like |
| <code>seteuid</code>. |
| |
| <p>The return values and error conditions are the same as for <code>seteuid</code>. |
| </p></blockquote></div> |
| |
| <!-- unistd.h --> |
| <!-- BSD --> |
| <div class="defun"> |
| — Function: int <b>setreuid</b> (<var>uid_t ruid, uid_t euid</var>)<var><a name="index-setreuid-3318"></a></var><br> |
| <blockquote><p>This function sets the real user ID of the process to <var>ruid</var> and the |
| effective user ID to <var>euid</var>. If <var>ruid</var> is <code>-1</code>, it means |
| not to change the real user ID; likewise if <var>euid</var> is <code>-1</code>, it |
| means not to change the effective user ID. |
| |
| <p>The <code>setreuid</code> function exists for compatibility with 4.3 BSD Unix, |
| which does not support file IDs. You can use this function to swap the |
| effective and real user IDs of the process. (Privileged processes are |
| not limited to this particular usage.) If file IDs are supported, you |
| should use that feature instead of this function. See <a href="Enable_002fDisable-Setuid.html#Enable_002fDisable-Setuid">Enable/Disable Setuid</a>. |
| |
| <p>The return value is <code>0</code> on success and <code>-1</code> on failure. |
| The following <code>errno</code> error conditions are defined for this |
| function: |
| |
| <dl> |
| <dt><code>EPERM</code><dd>The process does not have the appropriate privileges; you do not |
| have permission to change to the specified ID. |
| </dl> |
| </p></blockquote></div> |
| |
| </body></html> |
| |
