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<TITLE>setgid</TITLE>
<body bgcolor="#ffffcc">
<hr>
<pre>
<h3>SETGID(2) Linux Programmer's Manual SETGID(2)
</h3>
<h3>NAME
</h3> setgid - set group identity
<h3>SYNOPSIS
</h3> #include <unistd.h>
int setgid(gid_t gid)
<h3>DESCRIPTION
</h3> setgid sets the effective group ID of the current process.
If the caller is the superuser, the real and saved group
ID's are also set.
Under Linux, setgid is implemented like SYSV with
SAVED_IDS. This allows a setgid (other than root) program
to drop all of it's group privileges, do some un-privi-
leged work, and then re-engage the original effective
group ID in a secure manner.
If the user is root or the program is setgid root, special
care must be taken. The setgid function checks the effec-
tive gid of the caller and if it is the superuser, all
process related group ID's are set to gid. 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 gid does not
match the effective or saved group ID of the call-
ing process.
<h3>CONFORMING TO
</h3> System V
</pre>
<hr>
<h3>SEE ALSO
</h3><p>
<a href=getgid.htm>getgid</a>,
<a href=setregid.htm>setregid</a>,
<a href=setegid.htm>setegid</a>,
<pre>
<h3>Linux 1.1.36 29 July 1994 1
</h3>
</pre>
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