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

NAME
     setreuid - set real and effective user IDs

SYNOPSIS
     #include <unistd.h>

     int
     setreuid(uid_t ruid, uid_t euid);

DESCRIPTION
     The real and effective user IDs of the current process are set according
     to the arguments.	The saved user ID will be set to the new value of the
     real user ID if a real user ID is specified and either the new real user
     ID value is different from the current value or the effective user ID is
     changed to a value other than the current saved user ID.

     Unprivileged users may change either user ID to the current value of the
     real, effective, or saved user ID.	 Only the superuser may make other
     changes.

     Supplying a value of -1 for either the real or effective user ID forces
     the system to substitute the current ID in place of the -1 parameter.

     The setreuid() function was intended to allow swapping the real and
     effective user IDs in set-user-ID programs to temporarily relinquish the
     set-user-ID value.	 This purpose is now better served by the use of the
     seteuid(2) function.

     When setting the real and effective user IDs to the same value, the
     setuid(2) function is preferred.

RETURN VALUES
     Upon successful completion, a value of 0 is returned.  Otherwise, a value
     of -1 is returned and errno is set to indicate the error.

ERRORS
     [EPERM]	   The current process is not the superuser and a change other
		   than changing the effective user ID to the real user ID was
		   specified.

SEE ALSO
     getuid(2), seteuid(2), setregid(2), setresuid(2), setuid(2)

STANDARDS
     The setreuid() function conforms to the IEEE Std 1003.1-2001 (``POSIX'')
     and X/Open Portability Guide Issue 4.3 (``XPG4.3'').  specifications.

     Note, however, that prior to IEEE Std 1003.1-2001 (``POSIX''), the
     setreuid() function was not a part of the IEEE Std 1003.1 (``POSIX'')
     specification.  As a result, it may not be implemented on all systems.

HISTORY
     The setreuid() function call appeared in 4.2BSD.  A semantically
     different version appeared in 4.4BSD.  The current version, with the
     original semantics restored, appeared in OpenBSD 3.3.

CAVEATS
     The setreuid() function predates POSIX saved user IDs.  This
     implementation changes the saved user ID to the new value of the real
     user ID only if the real user ID is specified and either changed or the
     effective user ID is changed to a value other than the current saved user
     ID.  Other implementations may behave differently.

OpenBSD 4.9			August 4, 2008			   OpenBSD 4.9

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