The Built-in Debugger
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Invoking The Debugger
To debug a program, you would do something like this:
<![CDATA[
perl -d [other_switches] your_script [your_script_switches]
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Once there, you can type "h" to get the help
screen which looks like this (on NT anyway):
<![CDATA[
DB<1> h
T Stack trace.
s Single step.
n Next, steps over subroutine calls.
r Return from current subroutine.
c [line] Continue; optionally inserts a one-time-only breakpoint
at the specified line.
<CR> Repeat last n or s.
l min+incr List incr+1 lines starting at min.
l min-max List lines.
l line List line;
l List next window.
- List previous window.
w line List window around line.
l subname List subroutine.
f filename Switch to filename.
/pattern/ Search forwards for pattern; final / is optional.
?pattern? Search backwards for pattern.
L List breakpoints and actions.
S List subroutine names.
t Toggle trace mode.
b [line] [condition]
Set breakpoint; line defaults to the current execution line;
condition breaks if it evaluates to true, defaults to '1'.
b subname [condition]
Set breakpoint at first line of subroutine.
d [line] Delete breakpoint.
D Delete all breakpoints.
a [line] command
Set an action to be done before the line is executed.
Sequence is: check for breakpoint, print line if necessary,
do action, prompt user if breakpoint or step, evaluate line.
A Delete all actions.
V [pkg [vars]] List some (default all) variables in package (default current).
X [vars] Same as "V currentpackage [vars]".
< command Define command before prompt.
> command Define command after prompt.
! number Redo command (default previous command).
! -number Redo number'th to last command.
H -number Display last number commands (default all).
q or ^D Quit.
p expr Same as "print DB::OUT expr" in current package.
= [alias value] Define a command alias, or list current aliases.
command Execute as a perl statement in current package.
DB<1>
]]>
Use The Debugger
- Use the debugger.
- The debugger is your friend.
- It will save you lots of time.
- Don't sprinkle tons of "
print()" statements around.
- Learn the debugger.
- Be one with the debugger.
- Use the debugger.
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Last Modified: $Date: 1997/05/02 07:17:38 $