SUBROUTINE ST_NULL  ( string, outstr, lens, iret )
C************************************************************************
C* ST_NULL								*
C*									*
C* This subroutine appends a NULL character to the end of a string.	*
C* The input and output strings may be the same variable.  		*
C* If the string's length is equal to its dimensioned length, the last	*
C* character will be replaced by the NULL character.			*
C* The output length of the string does not include trailing blanks,	*
C* tabs, or nulls.							*
C*									*
C* ST_NULL  ( STRING, OUTSTR, LENS, IRET )				*
C*									*
C* Input parameters:							*
C*	STRING		CHAR*		String				*
C*									*
C* Output parameters:							*
C*	OUTSTR		CHAR*		String without blanks		*
C*	LENS		INTEGER		Length of output string		*
C*	IRET		INTEGER		Return code			*
C*				   	 0 = normal return 		*
C**									*
C* Log:									*
C* K. Tyle/GSC		12/96  Based on ST_LSTR 			*
C* K. Brill/EMC		11/98	Rewrote; use ST_LSTR			*
C************************************************************************
C*
	CHARACTER*(*)	string, outstr
C*
	CHARACTER	ttt*256
C-----------------------------------------------------------------------
	iret   = 0
	ttt = string
C
C*	Get the actual length of the output string.
C
	lenout = LEN ( outstr )
	IF ( lenout .eq. 0 ) THEN
	    outstr = ttt 
	    lens = lenout
	    RETURN
	END IF
	CALL ST_LSTR ( ttt, lng, ier )
	IF ( lng .eq. lenout ) THEN
	    outstr = ttt
	    lens = lng
	    RETURN
	END IF
	lens = lng + 1
	outstr = ttt
	outstr (lens:lens) = CHAR (0)
C*
	RETURN
	END