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on

Perform One or More Commands at Specified Locations

ABBREVIATION

o{n}

FORMAT

on HOOK-TYPE [when (EXPRESSION)] [count N] CMD | {CMD-LIST}

DESCRIPTION

The on command enables you to perform one or more debugger commands at various locations in your program.

In other words, you can issue a single debugger command (CMD) or a list of debugger commands ({CMD-LIST}) for the HOOK-TYPE argument. Chapter 3 explains the values you can use for the HOOK-TYPE argument, which is an argument that enables you to specify hook locations. The other arguments are explained here:

when

You can optionally use a when clause to give commands conditionally at hooks.

count N

The count N argument is optional. If count N is specified, the first N - 1 times the hook is reached, the count is decremented. The Nth time it is hit, the command is executed. After the Nth time, the command is executed every time the hook is hit.

If a when clause is present, a hit is counted only if the when expression is true.

A query command, issued before the count drops to 1, displays the current value of count. The word count can be abbreviated to cou{nt}.

CMD

CMD can contain any debugger command and its arguments. Abbreviations are accepted for the command also. (Note that on commands can be nested, as described in the next section.)

CMD-LIST

The CMD-LIST argument contains one or more of the commands and arguments separated by semicolons or new lines. CMD-LIST can contain nested on commands. CMD-LIST is enclosed by braces.

Commands that are part of the CMD-LIST argument can be entered on different lines. Use an open brace at the end of the first line, followed by the list of commands, and then a close brace. Note that if you put commands on separate lines, then the end of a line can be the command separator. You do not need a semicolon.

The following is a list of other points you need to know about the CMD-LIST arguments:

• When the exec command is used in a CMD-LIST, no other debugger command can occur on the same line following exec.

• If CMD-LIST contains the break command, then control over the restart of execution is turned over to you only after all the other commands in the list are performed.

• The debugger does not check the syntax of your CMD-LIST arguments until it is time to execute them. If you make a syntax mistake, it is not detected until the debugger tries to execute the command.
  • If a command name is syntactically incorrect, the debugger flushes the buffer for that command and any command after it. They are not executed. The debugger tells you about the commands that it did not execute and turns control over to you.

  • If you enter a command name that is syntactically correct, but the argument is invalid, the debugger does not flush the buffer. Instead, the debugger executes valid commands and tells you about the invalid argument via an error message.

  • If you make a mistake in the when clause of an on command, no commands from the CMD-LIST are executed. If any other on commands apply to this hook, they are not executed. The debugger turns control over to the user.

  • When used as part of a CMD-LIST, the escape command behaves like any other command in CMD-LIST. It is executed in order.

EXAMPLES

on entry print

prints the parameters on entry to all functions.

on main 45 print i, pxyz -->a

prints i and pxyz -->a at line 45 of the main function.

on 53 {print i; dump s str}

prints i and dumps the string pointed to by s at line 53 of the current function.

on (comp23) entry print

prints the parameters on entry to the functions in the comp23 compilation.

on func1 entry {where; print parm1, parm2};

issues a where command and prints parm1 and parm2 on entry to the func1 function.

SYSTEM DEPENDENCIES

Although the on command has no system dependencies, the behavior of commands used with on can have system dependencies. For example, the behavior of the escape, system, and exec commands used as CMD arguments or as part of CMD-LIST is system-dependent. See escape, exec (CMS), on, and system (CMS) for details.

COMMAND CAN BE ISSUED FROM

PROFILE	yes
configuration file	no
Source window prefix	none

SCOPE

The on command uses command scope to supply default identifiers, function names, and section names.

RETURN CODES SET

	Successful: request number
	Unsuccessful: 0

SEE ALSO

• auto

• break

• disable

• drop

• enable

• ignore

• trace

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Copyright © 2001 by SAS Institute Inc., Cary, NC, USA. All rights reserved.