SETREUID(2)                                         Linux Programmer's Manual                                        SETREUID(2)



NAME
       setreuid, setregid - set 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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       setreuid(), setregid(): _BSD_SOURCE || _XOPEN_SOURCE >= 500

DESCRIPTION
       setreuid() 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.

       Completely  analogously, setregid() 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.

ERRORS
       EPERM  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 setreuid() and setregid() function calls first appeared in 4.2BSD).

NOTES
       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
       setreuid(), 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  setregid(),  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.

SEE ALSO
       getgid(2), getuid(2), seteuid(2), setgid(2), setresuid(2), setuid(2), capabilities(7)

COLOPHON
       This  page  is  part of release 3.25 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                                                      2009-10-17                                                SETREUID(2)