subroutine event_display_write_control_file(ireturn_code)
c
c
c This routine writes a short control file indicating the frequency with
c which events should be written to disk for consumption by the display
c routine. 
c
c George Gollin, g-gollin@uiuc.edu, 1999.
c
c
#include "event_display_data.inc"
#include "event_display.inc"
c
c
      logical file_exists
c
c
c return code is 0 if I managed to write the file
c                1 if I couldn't open the file
c                2 if I couln't write to the opened file
c
c
      ireturn_code=0
c
c
c does the control file exist?  If so, I want to delete it, then recreate it.
c Do in a loop, in case file is busy and I can't delete it... keep trying.
      do itry=1,1000
      inquire(file=file_control(1:lenocc(file_control)), 
     .        exist=file_exists)
      if(file_exists) then 
         call system('rm '//file_control(1:lenocc(file_control)))
         else
         go to 5
         end if
      end do
c
c
 5    continue
c
c
c Now open the control file:
      open(lun_control, file=file_control(1:lenocc(file_control)),
     .     status='new', form='formatted', iostat=io_err)
c
c
c problems opening file?
      if(io_err .ne. 0) then
c
         print *,' event_display couldn.t open the control file',
     .        file_control
         print *,' iostat returned by open was... ',io_err
c
         ireturn_code=1
         return
         endif
c
c 
c so far so good: write the number to be read by Thierry's code to the file:
      write(lun_control, *, iostat=io_err1) number_for_control_file 
c
c also, for diagnostic purposes, write what I think the display's IP is...
      write(lun_control, *, iostat=io_err2) hostname
c
c
c problems writing the file?
      if(io_err1 .ne. 0 .or. io_err2 .ne. 0) then
c
         print *,
     .        ' event_display_write_control_file couldn.t write to',
     .        ' control file ',file_control(1:lenocc(file_control))
         print *,' iostat returned was... ',io_err1, io_err2
c
         ireturn_code=2
         close(lun_control, iostat=io_err)
         return
         endif
c
c
      close(lun_control, iostat=io_err)
      return
      end