ADAS Subroutine xxflnm

      SUBROUTINE XXFLNM( DSNIN  , DSNFUL , LEXIST )
C-----------------------------------------------------------------------
C
C  ****************** FORTRAN77 SUBROUTINE: XXFLNM *********************
C
C  PURPOSE: TO PREPARE A UNIX DATASET NAME FROM A STRING WHICH MAY
C           INCLUDE AN ADAS ENVIRONMENT LEADER AND COMMENTS.
C           THE ADAS ENVIRONMENT VARIABLE MUST BE FIRST AND IN DOUBLE
C           QUOTES.  THE COMMENTS MUST EITHER FOLLOW OR PRECEDE A COLON.
C
C  CALLING PROGRAM: GENERAL USE
C
C  SUBROUTINE:
C
C  INPUT : (C80)  DSNIN    = INPUT STRING FOR INTERROGATION
C
C  OUTPUT: (C80)  DSNFUL   = THE FULL EXPANDED FILE NAME WITHOUT
C                             EXTRANEOUS MATERIAL
C  OUTPUT: (L*4)  LEXIST   = .TRUE. => NAME FORMED AND FILE EXISTS
C                             .FALSE.=> FAILED TO FORM NAME OR FIND FILE
C
C          (C*80) DSN1     = WORK STRING
C          (C*80) DSNTEMP  = WORK STRING
C          (C*80) BLANK    = BLANK STRING
C          (I*4)   LEN1     = STRING INDEX
C          (I*4)   LEN2     = STRING INDEX
C          (I*4)   LEN3     = STRING INDEX
C          (I*4)   LEN4     = STRING INDEX
C
C ROUTINES:
C          ROUTINE    SOURCE   BRIEF DESCRIPTION
C          -------------------------------------------------------------
C          XXSLEN     ADAS     FIND BEGINNING AND END OF A STRING
C          I4UNIT     ADAS     FETCH UNIT NUMBER FOR OUTPUT OF MESSAGES
C          GETENV     UNIX     FETCH AN ENVIRONMENT VARIABLE
C
C
C AUTHOR:  H. P. SUMMERS, UNIVERSITY OF STRATHCLYDE
C          JA8.08
C          TEL. 0141-553-4196
C
C DATE  :  21/05/96
C
C UPDATE:
C
C VERSION: 1.1                          DATE: 29-05-96
C MODIFIED: WILLIAM OSBORN
C               - ADDED CODE FOR INITIAL COMMENTS AND PUT INTO S.C.C.S.
C
C-----------------------------------------------------------------------
C-----------------------------------------------------------------------
C

      CHARACTER*80        DSNFUL,      DSNIN
      LOGICAL             LEXIST