subroutine gtws(fnwin,nwin,ier)
c
c open window_file and get time windows
c a.tento 04/02 v.1.0
c a.tento 06/02 v.1.1 --> beginning and end of windows in #samples
c                   format index (mandatory) & station name (optional)
c a.tento 10/02 v.1.2 --> back tp beg. and end of windows in seconds
c a.tento 02/04 v.1.3 --> call split4: blank in file_names allowed
c                         provided that they are inside "  "
c a.tento 02/04 v.1.4 --> SAF default format 
c                         controlled error if window file is incorrect 
c
c
      implicit none
      character*200 fnwin
      integer  ier, nwin
c
      include 'main.h'
      include 'window.h'
c
      character row*1000,  argout(20)*200
      integer nunit, ierint,  i,  nw, j
      real wl
c
c
      call glun(nunit,ierint)
      if ( ierint .ne.  0 ) goto 99
      open(unit=nunit,file=fnwin,status='old',err=98)
c
      rmaxwl = 0.0
      rminwl = 1.0e+12
      nwin = 0
      n_windows = 0
c
      do 1 i = 1,  1000000
      read(nunit,100,end=10,err=97)row
      if(row(1:1) .eq.  '#' ) goto 1
c
      do 15 j = 1, 8
      argout(j) = ' '
15    continue
      call split4(row,argout,nw,ier)
        if ( ier .ne.  0 ) then
        write(*,*)' ERROR'
        write(*,*)' file_name incorrectly specified in window_file',
     #            ' at line:  ', i
        return
        endif
c
      if ( nw .eq. 0 ) goto 1 
        if ( nw .lt. 3 ) then
        ier = 1
        write(*,*)' ERROR'
        write(*,*)' missing item(s) in window_file at line:  ', i
        return
        endif
c
      nwin = nwin + 1
      n_windows = nwin
      data_file(nwin) = argout(1)
      read(argout(2),*) start_time(nwin)
      read(argout(3),*) end_time(nwin) 
c SAF : default format
        if ( nw .gt. 3 ) then
        read(argout(4),*) idfor(nwin)
        else
        idfor(nwin) = 2
        endif
      idV(nwin)       = argout(5)
      idN(nwin)       = argout(6)
      idE(nwin)       = argout(7)
      idsta(nwin)     = argout(8)
      wl = end_time(nwin) - start_time(nwin)
c.. wl = number of points / if wl in sec check in main when dt available
c.. NOW wl is in second 
c        if ( wl .lt. 1 )         goto 96
c        if ( wl .gt. maxwinlen ) goto 95
      rmaxwl = amax1(rmaxwl, wl)
      rminwl = amin1(rminwl, wl)
      if ( nwin .eq.  maxnwin ) goto  20
1     continue
20    close(nunit)
c
c ... read in maximun number of windows 
      write(*,*)' WARNING'
      write(*,*)' Number of windows greater than allowed  dimension'
      write(*,*)' Only the first ',nwin,'  windows  are used'
      ier = 2 
      return
c
c
10    continue
      close(nunit)
c
      ier = 0
      return
c
c ... error in getting an unused fortran file unit  
99    write(*,*)' GTWS : this error should be impossible'
      write(*,*)' no logical unit available'  
      ier = 1
      return
c
c ... error in opening window_file
98    write(*,*)' GTWS : error in opening window_file'
      ier = 3 
      return
c
c ... error in reading window_file
97    write(*,*)' GTWS : error in reading window_file'
      ier = 5 
      return
c
c ... window exceeding dimension
c95    write(*,*)' Requested window exceeds current dimension '
c      write(*,*)' requested # point : ', wl, ' current dimension',
c     #          maxwinlen
c      write(*,200)data_file(nwin)
c      ier = 7 
c      return
c
c ...  start time less then end time
c96    write(*,*)' Start sample or end sample incorrectly specified ',
c     #          ' Window number : ', nwin
c      write(*,*)' Start sample : ',start_time(nwin),
c     #          '  End sample :', end_time(nwin)
c      write(*,200)data_file(nwin)
c      ier = 9
c      return
c
c
c
100   format(a1000)
200   format(1x,a200)
c
      end