With each command it processes, Windows, OS/2 and Unix/Linux command shells produce a number called a return code. When a Rexx program is running, this return code is automatically assigned to a special built-in Rexx variable named RC.
If the command was processed without problems, the return code is almost always 0. If something goes wrong, the return code issued is a nonzero number. The number depends on the command itself and the error encountered.
This example shows how to display a return code:
| /* getrc&per;cmd report */ |
| "TYPE nosuch.fil" |
| say "the return code is" RC |
The special variable RC can be used in expressions like any other variable. In the next example, an error message is displayed when the TYPE command returns a nonzero value in RC:
| /* Simple if/then error handler */ |
| say "Type a file name:" |
| pull filename |
| "TYPE" filename |
| if RC \\= 0 |
| then say "Could not find" filename |
This program tells you only that the system could not find a nonexistent file.
A system error does not stop a Rexx program. Without some provision to stop the program, in this case a trap, Rexx continues running. You might have to press the Ctrl+Break key combination to stop processing. Rexx includes the following instructions for trapping and controlling system errors: