SETREUID(2) Linux Programmer's Manual SETREUID(2)
NAME
setreuid, setregid - set(7,n,1 builtins) real and/or effective user or group ID
SYNOPSIS
#include <sys/types.h>
#include <unistd.h>
int setreuid(uid_t ruid, uid_t euid);
int setregid(gid_t rgid, gid_t egid);
DESCRIPTION
setreuid sets real and effective user IDs of the current process.
Supplying a value of -1 for either the real or effective user ID forces
the system to leave that ID unchanged.
Unprivileged processes may only set(7,n,1 builtins) the effective user ID to the real
user ID, the effective user ID or the saved effective user ID.
POSIX: It is unspecified whether unprivileged processes may set(7,n,1 builtins) the
real user ID to the real user ID, the effective user ID or the saved
effective user ID.
Linux: Unprivileged users(1,5) may only set(7,n,1 builtins) the real user ID to the real
user ID or the effective user ID.
Linux: If the real user ID is set(7,n,1 builtins) or the effective user ID is set(7,n,1 builtins) to a
value not equal to the previous real user ID, the saved user ID will be
set(7,n,1 builtins) to the new effective user ID.
Completely analogously, setregid sets real and effective group ID's of
the current process, and all of the above holds with "group" instead of
"user".
RETURN VALUE
On success, zero is returned. On error(8,n), -1 is returned, and errno is
set(7,n,1 builtins) appropriately.
ERRORS
EPERM The current process is not privileged (Linux: does not have the
CAP_SETUID capability in(1,8) the case of setreuid(), or the CAP_SET-
GID capability in(1,8) the case of setregid()) and a change other
than (i) swapping the effective user (group) ID with the real
user (group) ID, or (ii) setting one to the value of the other
or (iii) setting the effective user (group) ID to the value of
the saved user (group) ID was specified.
NOTES
Setting the effective user (group) ID to the saved user ID is possible
since Linux 1.1.37 (1.1.38).
CONFORMING TO
BSD 4.3 (the setreuid and setregid function calls first appeared in(1,8)
4.2BSD).
SEE ALSO
getgid(2), getuid(2), seteuid(2), setgid(2), setresuid(2), setuid(2),
capabilities(7)
Linux 2.6 2004-07-04 SETREUID(2)