setuid,
seteuid,
setgid,
setegid —
set user and group ID
#include
<unistd.h>
int
setuid(
uid_t
uid);
int
seteuid(
uid_t
euid);
int
setgid(
gid_t
gid);
int
setegid(
gid_t
egid);
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.
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.
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.
getgid(2),
getuid(2),
issetugid(2),
setgroups(2),
setregid(2),
setresgid(2),
setresuid(2),
setreuid(2)
The
setuid(),
seteuid(),
setgid(), and
setegid() functions conform to
IEEE Std 1003.1-2008
(“POSIX.1”).
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.
![[OpenBSD]](/openbsd.gif){kind=small}