setreuid(2) [freebsd man page]

SETREUID(2)						      BSD System Calls Manual						       SETREUID(2)

NAME

     setreuid -- set real and effective user ID's

LIBRARY

     Standard C Library (libc, -lc)

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.  If ruid or euid is -1, the current uid is filled
     in by the system.	Unprivileged users may change the real user ID to the effective user ID and vice-versa; only the super-user may make other
     changes.

     If the real user ID is changed (i.e. ruid is not -1) or the effective user ID is changed to something other than the real user ID, then the
     saved user ID will be set to the effective user ID.

     The setreuid() system call has been used to swap 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) system call.

     When setting the real and effective user IDs to the same value, the standard setuid() system call is preferred.

RETURN VALUES

     The setreuid() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
     cate the error.

ERRORS

     [EPERM]		The current process is not the super-user and a change other than changing the effective user-id to the real user-id was
			specified.

SEE ALSO

     getuid(2), issetugid(2), seteuid(2), setuid(2)

HISTORY

     The setreuid() system call appeared in 4.2BSD.

BSD
								 February 8, 2001							       BSD

setreuid(2)							   System Calls 						       setreuid(2)

NAME

       setreuid - set real and effective user IDs

SYNOPSIS

       #include <unistd.h>

       int setreuid(uid_t ruid, uid_t euid);

DESCRIPTION

       The  setreuid()	function  is  used  to	set the real and effective user IDs of the calling process. If ruid is -1, the real user ID is not
       changed; if euid is -1, the effective user ID is not changed. The real and effective user IDs may be set to different values  in  the  same
       call.

       If  the {PRIV_PROC_SETID} privilege is asserted in the effective set of the calling process, the real user ID and the effective user ID can
       be set to any legal value.

       If the {PRIV_PROC_SETID} privilege is not asserted in the effective set of the calling process, either the real user ID can be set  to  the
       effective user ID, or the effective user ID can either be set to the saved set-user ID from execve() (seeexec(2)) or the real user ID.

       In  either  case,  if the real user ID is being changed (that is, if ruid is not  -1), or the effective user ID is being changed to a value
       not equal to the real user ID, the saved set-user ID is set equal to the new effective user ID.

       All privileges are required to change to uid 0.

RETURN VALUES

       Upon successful completion, 0 is returned. Otherwise, -1 is returned, errno is set to indicate the error, and neither of the user IDs  will
       be changed.

ERRORS

       The setreuid() function will fail if:

       EINVAL	       The value of ruid or euid is less than  0 or greater than UID_MAX (defined in <limits.h>).

       EPERM	       The  {PRIV_PROC_SETID}  privilege  is not asserted in the effective set of the calling processes and a change was specified
		       other than changing the real user ID to the effective user ID, or changing the effective user ID to the real user ID or the
		       saved set-user ID. See privileges(5) for additional restrictions which apply when changing to UID 0.

USAGE

       If  a set-user-ID process sets its effective user ID to its real user ID, it can still set its effective user ID back to the saved set-user
       ID.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       exec(2), getuid(2), setregid(2), setuid(2), attributes(5), privileges(5), standards(5)

SunOS 5.10							    22 Mar 2004 						       setreuid(2)