anchor.diff:         select case(trim(arg))
          case('-h','--help')
             ! print help and exit
  -          write(0,*) trim(syntax)
  +          write(0,100)
             error_code = 1
             return
          case('-i','--int','--fasta')
  
positive.code:     nargs = command_argument_count()
  
      if (nargs == 0) then
         ! no args: print syntax and stop
         write(0,*) trim(syntax)
         error_code = 1
         return
      end if
  
negative.code:   implicit none
    private
    public :: command_line_read
  
  contains
  
    subroutine command_line_read(udata, data_type, uwgt, wid, uprm, uchk, rseed, &
         beta, mc_nsweeps, nupdate, niter_agd, niter_gd, lambda,prefix, &
         error_code)
      use units, only: units_open, units_open_unf
      use arguments, only: read_opt, read_opt_arg
      integer,          intent(inout) :: udata
      character(len=*), intent(inout) :: data_type
      integer,          intent(inout) :: uwgt
      real(kflt),       intent(inout) :: wid
      integer,          intent(inout) :: uprm
      integer,          intent(inout) :: uchk
      integer,          intent(inout) :: rseed
      real(kflt),       intent(inout) :: beta
      integer,          intent(inout) :: mc_nsweeps
      integer,          intent(inout) :: nupdate
      integer,          intent(inout) :: niter_agd
      integer,          intent(inout) :: niter_gd
      real(kflt),       intent(inout) :: lambda
      character(len=*), intent(out) :: prefix
      integer,          intent(out) :: error_code
      integer                         :: err
      character(len=long_string_size) :: data_file
      character(len=long_string_size) :: ww_file
  