|| Linux Programmer's Manual
NAME setreuid, setregid - set real and/or effective user or group ID
Feature Test Macro Requirements for glibc (see
_BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
() sets real and effective user IDs of the calling 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 the effective user ID to the real user ID, the effective user ID, or the saved set-user-ID.
Unprivileged users may only set the real user ID to the real user ID or the effective user ID.
If the real user ID is set or the effective user ID is set to a value not equal to the previous real user ID, the saved set-user-ID will be set to the new effective user ID.
() sets real and effective group ID's of the calling process, and all of the above holds with "group" instead of "user".
RETURN VALUE On success, zero is returned. On error, -1 is returned, and
errno is set appropriately.
The calling process is not privileged (Linux: does not have the
CAP_SETUID capability in the case of
setreuid(), or the
CAP_SETGID capability in 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 set-user-ID (saved set-group-ID) was specified.
CONFORMING TO POSIX.1-2001, 4.3BSD (the
setregid() function calls first appeared in 4.2BSD).
Setting the effective user (group) ID to the saved set-user-ID (saved set-group-ID) is possible since Linux 1.1.37 (1.1.38).
POSIX.1 does not specify all of possible ID changes that are permitted on Linux for an unprivileged process. For
(), the effective user ID can be made the same as the real user ID or the save set-user-ID, and it is unspecified whether unprivileged processes may set the real user ID to the real user ID, the effective user ID, or the saved set-user-ID. For
(), the real group ID can be changed to the value of the saved set-group-ID, and the effective group ID can be changed to the value of the real group ID or the saved set-group-ID. The precise details of what ID changes are permitted vary across implementations.
POSIX.1 makes no specification about the effect of these calls on the saved set-user-ID and saved set-group-ID.
The original Linux
() system calls supported only 16-bit user and group IDs. Subsequently, Linux 2.4 added
(), supporting 32-bit IDs. The glibc
() wrapper functions transparently deal with the variations across kernel versions.
COLOPHON This page is part of release 3.53 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/.