NAME
setuid, seteuid,
setgid, setegid —
set user and group ID
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 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
The setuid(),
seteuid(), setgid(), and
setegid() functions return the value 0 if
successful; otherwise the value -1 is returned and the global
variable errno is set to indicate the error.
ERRORS
setuid() and
seteuid() will succeed unless:
- [
EPERM] - The user is not the superuser and the requested uid or euid is not the process's real, effective, or saved UID.
setgid() and
setegid() will succeed unless:
- [
EPERM] - The user is not the superuser and the requested gid or egid is not the process's real, effective, or saved GID.
SEE ALSO
getgid(2), getuid(2), issetugid(2), setgroups(2), setregid(2), setresgid(2), setresuid(2), setreuid(2)
STANDARDS
The setuid(),
seteuid(), setgid(), and
setegid() functions conform to IEEE
Std 1003.1-2008 (“POSIX.1”).
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.