NAME
setuid, seteuid,
setgid, setegid —
set user and group ID
SYNOPSIS
#include
<sys/types.h>
#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 effective user
ID is that of the superuser, or if the specified user ID is the same as the
effective user ID. If not, but the specified user ID is the same as the real
user ID, setuid() will set the effective user ID to
the real user ID.
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 effective user
ID is that of the superuser, or if the specified group ID is the same as the
effective group ID. If not, but the specified group ID is the same as the
real group ID, setgid() will set the effective group
ID to the real group ID. 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 superuser, or the UID specified is not the real, effective, or saved ID, these functions return -1.
SEE ALSO
getgid(2), getuid(2), issetugid(2), setgroups(2), setregid(2), setresgid(2), setresuid(2), setreuid(2)
STANDARDS
The setuid() and
setgid() functions are compliant with the
IEEE Std 1003.1-1990 (“POSIX.1”)
specification with _POSIX_SAVED_IDS defined, with
the extensions allowed in section B.4.2.2. The
seteuid() and setegid()
functions are extensions based on the POSIX concept of
_POSIX_SAVED_IDS, and have been proposed for a
future revision of the standard.
HISTORY
The setuid() system call first appeared in
Version 1 AT&T UNIX;
setgid() in Version 4
AT&T UNIX; and seteuid() and
setegid() in 4.2BSD.