int
setuid(
uid_t uid
)
int
seteuid(
uid_t euid
)
int
setgid(
gid_t gid
)
int
setegid(
gid_t egid
)
)
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.
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.
)
and
setgid(
)
functions are compliant with the
ISO/IEC 9945-1:1990 (``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'') .