#define _GNU_SOURCE /* See feature_test_macros(7) */
int setresuid(uid_t ruid, uid_t euid, uid_t suid);
int setresgid(gid_t rgid, gid_t egid, gid_t sgid);
setresuid() sets the real user ID, the effective user ID, and the saved
set-user-ID of the calling process.
Unprivileged user processes may change the real UID, effective UID, and
saved set-user-ID, each to one of: the current real UID, the current
effective UID or the current saved set-user-ID.
Privileged processes (on Linux, those having the CAP_SETUID capability)
may set the real UID, effective UID, and saved set-user-ID to arbitrary
If one of the arguments equals -1, the corresponding value is not
Regardless of what changes are made to the real UID, effective UID, and
saved set-user-ID, the filesystem UID is always set to the same value
as the (possibly new) effective UID.
Completely analogously, setresgid() sets the real GID, effective GID,
and saved set-group-ID of the calling process (and always modifies the
filesystem GID to be the same as the effective GID), with the same
restrictions for unprivileged processes.
On success, zero is returned. On error, -1 is returned, and errno is
EAGAIN uid does not match the current UID and this call would bring
that user ID over its RLIMIT_NPROC resource limit.
EPERM The calling process is not privileged (did not have the
CAP_SETUID capability) and tried to change the IDs to values
that are not permitted.
These calls are available under Linux since Linux 2.1.44.
These calls are nonstandard; they also appear on HP-UX and some of the
Under HP-UX and FreeBSD, the prototype is found in <unistd.h>. Under
Linux the prototype is provided by glibc since version 2.3.2.
This page is part of release 3.54 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2010-11-22 SETRESUID(2)
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