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 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED

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.

       The  original  Linux  setreuid()  and  setregid()  system calls supported only 16-bit user and group IDs.
       Subsequently, Linux 2.4 added setreuid32() and setregid32(), supporting 32-bit IDs.  The glibc setreuid()
       and setregid() wrapper functions transparently deal with the variations across kernel versions.

SEE ALSO

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

COLOPHON

       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/.