First of all, have you tried using the B<-w> switch?
+
+If you're new to the Perl debugger, you may prefer to read
+L<perldebtut>, which is a tutorial introduction to the debugger .
+
=head1 The Perl Debugger
If you invoke Perl with the B<-d> switch, your script runs under the
=over 12
+=item h
+
+Prints out a summary help message
+
=item h [command]
-Prints out a help message.
+Prints out a help message for the given debugger command.
-If you supply another debugger command as an argument to the C<h> command,
-it prints out the description for just that command. The special
-argument of C<h h> produces a more compact help listing, designed to fit
-together on one screen.
+=item h h
-If the output of the C<h> command (or any command, for that matter) scrolls
+The special argument of C<h h> produces the entire help page, which is quite long.
+
+If the output of the C<h h> command (or any command, for that matter) scrolls
past your screen, precede the command with a leading pipe symbol so
that it's run through your pager, as in
- DB> |h
+ DB> |h h
+
+You may change the pager which is used via C<o pager=...> command.
-You may change the pager which is used via C<O pager=...> command.
=item p expr
The C<DB::OUT> filehandle is opened to F</dev/tty>, regardless of
where STDOUT may be redirected to.
-=item x expr
+=item x [maxdepth] expr
-Evaluates its expression in list context and dumps out the result
-in a pretty-printed fashion. Nested data structures are printed out
-recursively, unlike the real C<print> function in Perl.
+Evaluates its expression in list context and dumps out the result in a
+pretty-printed fashion. Nested data structures are printed out
+recursively, unlike the real C<print> function in Perl. When dumping
+hashes, you'll probably prefer 'x \%h' rather than 'x %h'.
See L<Dumpvalue> if you'd like to do this yourself.
The output format is governed by multiple options described under
-L<"Options">.
+L<"Configurable Options">.
+
+If the C<maxdepth> is included, it must be a numeral I<N>; the value is
+dumped only I<N> levels deep, as if the C<dumpDepth> option had been
+temporarily set to I<N>.
=item V [pkg [vars]]
Same as C<V currentpackage [vars]>.
+=item y [level [vars]]
+
+Display all (or some) lexical variables (mnemonic: C<mY> variables)
+in the current scope or I<level> scopes higher. You can limit the
+variables that you see with I<vars> which works exactly as it does
+for the C<V> and C<X> commands. Requires the C<PadWalker> module
+version 0.08 or higher; will warn if this isn't installed. Output
+is pretty-printed in the same style as for C<V> and the format is
+controlled by the same options.
+
=item T
Produce a stack backtrace. See below for details on its output.
List previous window of lines.
-=item w [line]
+=item v [line]
-List window (a few lines) around the current line.
+View a few lines of code around the current line.
=item .
=item /pattern/
Search forwards for pattern (a Perl regex); final / is optional.
+The search is case-insensitive by default.
=item ?pattern?
Search backwards for pattern; final ? is optional.
+The search is case-insensitive by default.
-=item L
+=item L [abw]
-List all breakpoints and actions.
+List (default all) actions, breakpoints and watch expressions
=item S [[!]regex]
Trace through execution of C<expr>.
See L<perldebguts/"Frame Listing Output Examples"> for examples.
+=item b
+
+Sets breakpoint on current line
+
=item b [line] [condition]
-Set a breakpoint before the given line. If I<line> is omitted, set a
-breakpoint on the line about to be executed. If a condition
+Set a breakpoint before the given line. If a condition
is specified, it's evaluated each time the statement is reached: a
breakpoint is taken only if the condition is true. Breakpoints may
only be set on lines that begin an executable statement. Conditions
Sets a breakpoint before the first statement executed after the specified
subroutine is compiled.
-=item d [line]
+=item B line
-Delete a breakpoint from the specified I<line>. If I<line> is omitted, deletes
-the breakpoint from the line about to be executed.
+Delete a breakpoint from the specified I<line>.
-=item D
+=item B *
Delete all installed breakpoints.
a 53 print "DB FOUND $foo\n"
-=item a [line]
+=item A line
-Delete an action from the specified line. If I<line> is omitted, delete
-the action on the line that is about to be executed.
+Delete an action from the specified line.
-=item A
+=item A *
Delete all installed actions.
-=item W expr
+=item w expr
Add a global watch-expression. We hope you know what one of these
-is, because they're supposed to be obvious. B<WARNING>: It is far
-too easy to destroy your watch expressions by accidentally omitting
-the I<expr>.
+is, because they're supposed to be obvious.
-=item W
+=item W expr
+
+Delete watch-expression
+
+=item W *
Delete all watch-expressions.
-=item O booloption ...
+=item o
+
+Display all options
+
+=item o booloption ...
Set each listed Boolean option to the value C<1>.
-=item O anyoption? ...
+=item o anyoption? ...
Print out the value of one or more options.
-=item O option=value ...
+=item o option=value ...
Set the value of one or more options. If the value has internal
-whitespace, it should be quoted. For example, you could set C<O
+whitespace, it should be quoted. For example, you could set C<o
pager="less -MQeicsNfr"> to call B<less> with those specific options.
You may use either single or double quotes, but if you do, you must
escape any embedded instances of same sort of quote you began with,
as well as any escaping any escapes that immediately precede that
quote but which are not meant to escape the quote itself. In other
words, you follow single-quoting rules irrespective of the quote;
-eg: C<O option='this isn\'t bad'> or C<O option="She said, \"Isn't
+eg: C<o option='this isn\'t bad'> or C<o option="She said, \"Isn't
it?\"">.
For historical reasons, the C<=value> is optional, but defaults to
1 only where it is safe to do so--that is, mostly for Boolean
options. It is always better to assign a specific value using C<=>.
The C<option> can be abbreviated, but for clarity probably should
-not be. Several options can be set together. See L<"Options"> for
-a list of these.
+not be. Several options can be set together. See L<"Configurable Options">
+for a list of these.
=item < ?
=item ! pattern
Redo last command that started with pattern.
-See C<O recallCommand>, too.
+See C<o recallCommand>, too.
=item !! cmd
Run cmd in a subprocess (reads from DB::IN, writes to DB::OUT) See
-C<O shellBang>, also. Note that the user's current shell (well,
+C<o shellBang>, also. Note that the user's current shell (well,
their C<$ENV{SHELL}> variable) will be used, which can interfere
with proper interpretation of exit status or signal and coredump
information.
+=item source file
+
+Read and execute debugger commands from I<file>.
+I<file> may itself contain C<source> commands.
+
=item H -number
Display last n commands. Only commands longer than one character are
expression. The expression may evaluated to a reference to a
blessed object, or to a package name.
+=item M
+
+Displays all loaded modules and their versions
+
+
=item man [manpage]
Despite its name, this calls your system's default documentation
=head2 Configurable Options
-The debugger has numerous options settable using the C<O> command,
+The debugger has numerous options settable using the C<o> command,
either interactively or from the environment or an rc file.
+(./.perldb or ~/.perldb under Unix.)
+
=over 12
Length to truncate the argument list when the C<frame> option's
bit 4 is set.
+=item C<windowSize>
+
+Change the size of code list window (default is 10 lines).
+
=back
The following options affect what happens with C<V>, C<X>, and C<x>
Print only first N elements ('' for all).
+=item C<dumpDepth>
+
+Limit recursion depth to N levels when dumping structures.
+Negative values are interpreted as infinity. Default: infinity.
+
=item C<compactDump>, C<veryCompact>
Change the style of array and hash output. If C<compactDump>, short array
=back
-During startup, options are initialized from C<$ENV{PERLDB_OPTS}>.
-You may place the initialization options C<TTY>, C<noTTY>,
-C<ReadLine>, and C<NonStop> there.
+After the rc file is read, the debugger reads the C<$ENV{PERLDB_OPTS}>
+environment variable and parses this as the remainder of a `O ...'
+line as one might enter at the debugger prompt. You may place the
+initialization options C<TTY>, C<noTTY>, C<ReadLine>, and C<NonStop>
+there.
If your rc file contains:
Other examples include
- $ PERLDB_OPTS="NonStop frame=2" perl -d myprogram
+ $ PERLDB_OPTS="NonStop LineInfo=listing frame=2" perl -d myprogram
which runs script non-interactively, printing info on each entry
into a subroutine and each executed line into the file named F<listing>.
The debugger probably contains enough configuration hooks that you
won't ever have to modify it yourself. You may change the behaviour
-of debugger from within the debugger using its C<O> command, from
+of debugger from within the debugger using its C<o> command, from
the command line via the C<PERLDB_OPTS> environment variable, and
from customization files.
it must be owned by the superuser or the current user, and writable
by no one but its owner.
+You can mock TTY input to debugger by adding arbitrary commands to
+@DB::typeahead. For example, your F<.perldb> file might contain:
+
+ sub afterinit { push @DB::typeahead, "b 4", "b 6"; }
+
+Which would attempt to set breakpoints on lines 4 and 6 immediately
+after debugger initilization. Note that @DB::typeahead is not a supported
+interface and is subject to change in future releases.
+
If you want to modify the debugger, copy F<perl5db.pl> from the
Perl library to another name and hack it to your heart's content.
You'll then want to set your C<PERL5DB> environment variable to say
=head1 Debugging regular expressions
-C<use re 'debug'> enables you to see the gory details of how the
-Perl regular expression engine works. In order to understand this
-typically voluminous output, one must not only have some idea about
-about how regular expression matching works in general, but also
-know how Perl's regular expressions are internally compiled into
-an automaton. These matters are explored in some detail in
+C<use re 'debug'> enables you to see the gory details of how the Perl
+regular expression engine works. In order to understand this typically
+voluminous output, one must not only have some idea about how regular
+expression matching works in general, but also know how Perl's regular
+expressions are internally compiled into an automaton. These matters
+are explored in some detail in
L<perldebguts/"Debugging regular expressions">.
=head1 Debugging memory usage
You did try the B<-w> switch, didn't you?
+L<perldebtut>,
L<perldebguts>,
L<re>,
L<DB>,
-L<Devel::Dprof>,
+L<Devel::DProf>,
L<dprofpp>,
L<Dumpvalue>,
and
that were not compiled by Perl, such as those from C or C++ extensions.
If you alter your @_ arguments in a subroutine (such as with C<shift>
-or C<pop>, the stack backtrace will not show the original values.
+or C<pop>), the stack backtrace will not show the original values.
The debugger does not currently work in conjunction with the B<-W>
command-line switch, because it itself is not free of warnings.
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