#!/usr/local/rexx/rxx
/*
 * BACKSPACE
 *
 * A filter program to remove embedded backspaces and the characters
 * that preceed them from a file.
 *
 * Execute the program by typing
 *
 *      backspace <filename> <trace option>
 *
 * where <filename> is the name of the file containing the embedded
 * characters and <trace option> is one of the uni-REXX TRACE
 * options (all, error, etc.)
 *
 * The results of running the BACKSPACE program are directed to
 * standard output (the terminal screen) unless redirected elsewhere.
 *
 * For example, if you redirected the output of a "man" page to
 * a file named "output", you may see embedded backspaces in the
 * file when you edit it.  To remove these characters for better
 * readability, you would run the backspace program.
 *
 *     backspace output
 *
 * The <trace option> may be omitted.  If you choose to use the
 * option, you may enter the following
 *
 *     backspace output i
 *
 * The 'i' turns intermediate tracing on.
 */

parse arg f t
trace value t
do while lines(f)>0
  l = linein(f)
  do forever
    i = index(l,x2c('08'))             /* find a backspace character */
    if i>0
    then do
         h = left(l,i-2)               /* take out the backspace     */
         t = substr(l,i+1)             /* and the character that     */
         l = h||t                      /* immediately preceeded it   */
         end
    else leave        /* if no more backspaces, done with this line  */
    end
  call lineout , l
  end
call lineout                           /* close the output file      */