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<TITLE>setuid</TITLE>
<body bgcolor="#ffffcc">
<hr>
<pre>
<h3>SETUID(2) Linux Programmer's Manual SETUID(2)
</h3>
<h3>NAME
</h3> setuid - set user identity
<h3>SYNOPSIS
</h3> #include <unistd.h>
int setuid(uid_t uid)
<h3>DESCRIPTION
</h3> setuid sets the effective user ID of the current process.
If the caller is the superuser, the real and saved user
ID's are also set.
Under Linux, setuid is implemented like SYSV with
SAVED_IDS. This allows a setuid (other than root) program
to drop all of it's user privileges, do some un-privileged
work, and then re-engage the original effective user ID in
a secure manner.
If the user is root or the program is setuid root, special
care must be taken. The setuid function checks the effec-
tive uid of the caller and if it is the superuser, all
process related user ID's are set to uid. After this has
occurred, it is impossible for the program to regain root
privileges.
<h3>RETURN VALUE
</h3> On success, zero is returned. On error, -1 is returned,
and errno is set appropriately.
<h3>ERRORS
</h3> EPERM The user is not the super-user, and uid does not
match the effective or saved user ID of the call-
ing process.
<h3>CONFORMING TO
</h3> System V
</pre>
<hr>
<h3>SEE ALSO
</h3><p>
<a href=getuid.htm>getuid</a>,
<a href=setreuid.htm>setreuid</a>,
<a href=seteuid.htm>seteuid</a>,
<pre>
<h3>Linux 1.1.36 29 July 1994 1
</h3>
</pre>
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