Commonly Used Debugging Commands

Perl Tutorials - Herong's Tutorial Examples

∟Commonly Used Debugging Commands

This section describes how to run the Perl built-in debugger with the 'perl -d' option. Commonly used debugging commands are also provided.

The default Perl engine on Linux systems offers a built-in debugging tool. It is an interact command line driven and source line level debugger. To invoke the debugger, you need to run Perl with the debug option: -d. For example, "perl -d MyProgram.pl".

The ActivePerl engine for Windows systems also offers the same built-in debugging tool.

When a Perl program is executed with the debug option, execution will be stopped at the first executable statement and a debug command prompt will be displayed ready to take your debug commands.

Commonly used debugging commands:

h - Printing help information.
l - Listing next 10 lines of source file.
n - Executing the program until the next statement in the same code unit. This is called step-over in many other debugging environments.
s - Executing a single statement until the next statement in the same code unit or a subroutine unit called by the current statement. This is called step-into in many other debugging environments.
p exp - Printing the value of the expression: exp, in a scalar context.
x exp - Printing the value of the expression: exp, in a list context, and in a nicely formatted way.
b - Setting a breakpoint at the current statement.
b line - Setting a breakpoint at the statement of the specified line.
d - Deleting the breakpoint at the current statement.
d line - Deleting the breakpoint at the statement of the specified line.
c - Continuing the execution until the next statement with a breakpoint.
q - Quitting the debugger environment.