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SETREUID(3P)               POSIX Programmer's Manual              SETREUID(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       setreuid - set real and effective user IDs
SYNOPSIS
       #include <unistd.h>
       int setreuid(uid_t ruid, uid_t euid);

DESCRIPTION
       The setreuid() function shall set the real and effective  user  IDs  of
       the  current process to the values specified by the ruid and euid argu-
       ments. If ruid or euid is -1, the corresponding effective or real  user
       ID of the current process shall be left unchanged.
       A  process  with appropriate privileges can set either ID to any value.
       An unprivileged process can only set the effective user ID if the  euid
       argument  is  equal  to either the real, effective, or saved user ID of
       the process.
       It is unspecified whether a process without appropriate  privileges  is
       permitted  to change the real user ID to match the current real, effec-
       tive, or saved set-user-ID of the process.
RETURN VALUE
       Upon successful completion, 0 shall be returned. Otherwise, -1 shall be
       returned and errno set to indicate the error.
ERRORS
       The setreuid() function shall fail if:
       EINVAL The  value  of  the  ruid or euid argument is invalid or out-of-
              range.
       EPERM  The current process does not have  appropriate  privileges,  and
              either  an attempt was made to change the effective user ID to a
              value other than the real user ID or the saved set-user-ID or an
              attempt  was made to change the real user ID to a value not per-
              mitted by the implementation.

       The following sections are informative.
EXAMPLES
   Setting the Effective User ID to the Real User ID
       The following example sets the effective user ID of the calling process
       to  the  real user ID, so that files created later will be owned by the
       current user.

              #include <unistd.h>
              #include <sys/types.h>
              ...
              setreuid(getuid(), getuid());
              ...
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       getegid(), geteuid(), getgid(), getuid(),  setegid(),  seteuid(),  set-
       gid(),   setregid(),   setuid(),   the   Base   Definitions  volume  of
       IEEE Std 1003.1-2001, <unistd.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
       event of any discrepancy between this version and the original IEEE and
       The Open Group Standard, the original IEEE and The Open Group  Standard
       is  the  referee document. The original Standard can be obtained online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                         SETREUID(3P)