15. Tracing

I Full details of how to use Rexx's tracing facility are contained in
I rexx.ref.
O More details of how to use Rexx's tracing facility can be found in the
O OS/2 help system (help rexx trace).

  If a program goes wrong and you need more information in order to work out
  why, then Rexx provides you with the ability to trace all or part of your
  program to see what is happening.

  The most common form of tracing is turned on by

      trace r

  This causes each instruction to be listed before it is executed. Also, it
  displays the results of each calculation after it has been found.

  Another useful trace command is:

      trace ?a

  This makes the interpreter list the next instruction and then stop.
  You can continue to the next instruction by pressing return, or you
  can type in some Rexx to be interpreted, after which the interpreter
  will pause again.  You can use this to examine the program's variables
  and so forth.

  If you want the interpreter to stop only when passing a label, use:

     trace ?l

  This is useful for setting breakpoints in the program, or for making the
  program stop at a function call.