NAME
setuid,
seteuid,
setgid,
setegid —
set user and group
ID
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <unistd.h>
int
setuid(
uid_t
uid);
int
seteuid(
uid_t
euid);
int
setgid(
gid_t
gid);
int
setegid(
gid_t
egid);
DESCRIPTION
The
setuid() function sets the real and effective user IDs and
the saved set-user-ID of the current process to the specified value. The
setuid() function is permitted if the specified ID is equal
to the real user ID of the process, or if the effective user ID is that of the
super user.
The
setgid() function sets the real and effective group IDs
and the saved set-group-ID of the current process to the specified value. The
setgid() function is permitted if the specified ID is equal
to the real group ID of the process, or if the effective user ID is that of
the super user. Supplementary group IDs remain unchanged.
The
seteuid() function (
setegid()) sets the
effective user ID (group ID) of the current process. The effective user ID may
be set to the value of the real user ID or the saved set-user-ID (see
intro(2) and
execve(2)); in this way, the
effective user ID of a set-user-ID executable may be toggled by switching to
the real user ID, then re-enabled by reverting to the set-user-ID value.
Similarly, the effective group ID may be set to the value of the real group ID
or the saved set-group-ID.
RETURN VALUES
Upon success, these functions return 0; otherwise -1 is returned.
If the user is not the super user, or the uid specified is not the real,
effective ID, or saved ID, these functions return -1.
SEE ALSO
getgid(2),
getgroups(2),
getuid(2)
STANDARDS
The
setuid() and
setgid() functions are
compliant with the
IEEE Std 1003.1-1990
(“POSIX.1”) specification with
_POSIX_SAVED_IDS
not defined. We do not implement the
_POSIX_SAVED_IDS
option as specified in the standard
because this would make it impossible for a set-user-ID executable owned by a
user other than the super-user to permanently revoke its privileges.
The
seteuid() and
setegid() functions are
compliant with
IEEE Std 1003.1-2001
(“POSIX.1”).
HISTORY
The
setuid() and
setgid() functions appeared
in
Version 2 AT&T UNIX and
Version 4 AT&T UNIX, respectively.