mat_files Subroutine

subroutine mat_files(lunit,iname,status)
integer                      :: lunit             ! logical unit number
                                                  ! if LUNIT is zero, return
                                                  ! if LUNIT = standard input, return
                                                  ! if LUNIT = standard output, return
                                                  ! if LUNIT is positive, open the unit to file name INAME
                                                  ! if LUNIT is negative, close the unit number
integer                      :: iname(GG_LINELEN) ! INAME = FILE NAME, 1 character per word
                                                  ! how to know length of iname?
character(len=1024)          :: name
character(len=*),optional    :: status
character(len=20)            :: status_local
integer                      :: ios
   if(present(status))then
      status_local=status
   else
      status_local='UNKNOWN'
   endif

   G_FILE_OPEN_ERROR=.false.
   select case(lunit)
    case(0)      ! error catcher
    case(stdin)  ! if unit is standard input return
    case(stdout) ! if unit is standard output return
    case(8)      ! diary file
       call mat_buf2str(name,iname,GG_LINELEN)
       call journal('O',trim(name)) ! open up trail file
    case(:-1)
      if(lunit.eq.-8)then
         call journal('O','')                                        ! close trail file
      else                                                           ! if LUNIT is negative, close the unit
         ios=0
         flush(unit=-lunit,iostat=ios)
         if(-lunit.ne.STDIN)then
            close(unit=-lunit,iostat=ios)
         endif
      endif
    case default                                                     !  ALL OTHER FILES
      call mat_buf2str(name,iname,GG_LINELEN)
      if(lunit.ne.STDIN)then
         open(unit=lunit,file=name,status=status_local,iostat=ios)      ! open a file
         if(ios.ne.0)then                                               ! general file open failure
            call journal('OPEN failed on file '//name)
            G_FILE_OPEN_ERROR=.true.                                    ! set the flag a file error occurred
            G_RIO=G_INPUT_LUN                                           ! set current file to read input lines from/to G_INPUT_LUN
         else
            G_FILE_OPEN_ERROR=.false.                                   ! set the flag a file error did not occur
         endif
      endif
   end select
end subroutine mat_files