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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);

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 the effective user ID to  the  real
       user ID, the effective user ID or the saved set-user-ID.

       POSIX:  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.

       Linux:  Unprivileged  users  may  only set the real user ID to the real
       user ID or the effective user ID.

       Linux: 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 current 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  current 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.

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).

CONFORMING TO

       4.3BSD  (the setreuid() and setregid() function calls first appeared in
       4.2BSD).

SEE ALSO

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