If gid is equal to the real group ID or the saved set-group-ID,
or if the process has appropriate privileges,
setegid() shall set the effective group ID of the calling process
to gid; the real group ID, saved set-group-ID, and
any supplementary group IDs shall remain unchanged.
The setegid() function shall not affect the supplementary group
list in any way.
Upon successful completion, 0 shall be returned; otherwise, -1 shall
be returned and errno set to indicate the error.
The setegid() function shall fail if:
The value of the gid argument is invalid and is not supported
by the implementation.
The process does not have appropriate privileges and gid does
not match the real group ID or the saved
The following sections are informative.
Refer to the RATIONALE section in setuid() .
exec() , getegid() , geteuid() , getgid()
, getuid() ,
seteuid() , setgid() , setregid() , setreuid()
, setuid() ,
the Base Definitions volume of IEEE Std 1003.1-2001, <sys/types.h>,
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at