perldebug.1

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Run the debugger command, piping \s-1DB::OUT\s0 into your current pager.
.IP "||dbcmd" 12
.IX Xref "debugger command, ||"
.IX Item "||dbcmd"
Same as \f(CW\*(C`|dbcmd\*(C'\fR but \s-1DB::OUT\s0 is temporarily \f(CW\*(C`select\*(C'\fRed as well.
.IP "= [alias value]" 12
.IX Xref "debugger command, ="
.IX Item "= [alias value]"
Define a command alias, like
.Sp
.Vb 1
\&    = quit q
.Ve
.Sp
or list current aliases.
.IP "command" 12
.IX Item "command"
Execute command as a Perl statement.  A trailing semicolon will be
supplied.  If the Perl statement would otherwise be confused for a
Perl debugger, use a leading semicolon, too.
.IP "m expr" 12
.IX Xref "debugger command, m"
.IX Item "m expr"
List which methods may be called on the result of the evaluated
expression.  The expression may evaluated to a reference to a
blessed object, or to a package name.
.IP "M" 12
.IX Xref "debugger command, M"
.IX Item "M"
Displays all loaded modules and their versions
.IP "man [manpage]" 12
.IX Xref "debugger command, man"
.IX Item "man [manpage]"
Despite its name, this calls your system's default documentation
viewer on the given page, or on the viewer itself if \fImanpage\fR is
omitted.  If that viewer is \fBman\fR, the current \f(CW\*(C`Config\*(C'\fR information
is used to invoke \fBman\fR using the proper \s-1MANPATH\s0 or \fB\-M\fR\ \fImanpath\fR option.  Failed lookups of the form \f(CW\*(C`XXX\*(C'\fR that match
known manpages of the form \fIperlXXX\fR will be retried.  This lets
you type \f(CW\*(C`man debug\*(C'\fR or \f(CW\*(C`man op\*(C'\fR from the debugger.
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On systems traditionally bereft of a usable \fBman\fR command, the
debugger invokes \fBperldoc\fR.  Occasionally this determination is
incorrect due to recalcitrant vendors or rather more felicitously,
to enterprising users.  If you fall into either category, just
manually set the \f(CW$DB::doccmd\fR variable to whatever viewer to view
the Perl documentation on your system.  This may be set in an rc
file, or through direct assignment.  We're still waiting for a
working example of something along the lines of:
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.Vb 1
\&    $DB::doccmd = \*(Aqnetscape \-remote http://something.here/\*(Aq;
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.Sh "Configurable Options"
.IX Subsection "Configurable Options"
The debugger has numerous options settable using the \f(CW\*(C`o\*(C'\fR command,
either interactively or from the environment or an rc file.
(./.perldb or ~/.perldb under Unix.)
.ie n .IP """recallCommand""\fR, \f(CW""ShellBang""" 12
.el .IP "\f(CWrecallCommand\fR, \f(CWShellBang\fR" 12
.IX Xref "debugger option, recallCommand debugger option, ShellBang"
.IX Item "recallCommand, ShellBang"
The characters used to recall command or spawn shell.  By
default, both are set to \f(CW\*(C`!\*(C'\fR, which is unfortunate.
.ie n .IP """pager""" 12
.el .IP "\f(CWpager\fR" 12
.IX Xref "debugger option, pager"
.IX Item "pager"
Program to use for output of pager-piped commands (those beginning
with a \f(CW\*(C`|\*(C'\fR character.)  By default, \f(CW$ENV{PAGER}\fR will be used.
Because the debugger uses your current terminal characteristics
for bold and underlining, if the chosen pager does not pass escape
sequences through unchanged, the output of some debugger commands
will not be readable when sent through the pager.
.ie n .IP """tkRunning""" 12
.el .IP "\f(CWtkRunning\fR" 12
.IX Xref "debugger option, tkRunning"
.IX Item "tkRunning"
Run Tk while prompting (with ReadLine).
.ie n .IP """signalLevel""\fR, \f(CW""warnLevel""\fR, \f(CW""dieLevel""" 12
.el .IP "\f(CWsignalLevel\fR, \f(CWwarnLevel\fR, \f(CWdieLevel\fR" 12
.IX Xref "debugger option, signalLevel debugger option, warnLevel debugger option, dieLevel"
.IX Item "signalLevel, warnLevel, dieLevel"
Level of verbosity.  By default, the debugger leaves your exceptions
and warnings alone, because altering them can break correctly running
programs.  It will attempt to print a message when uncaught \s-1INT\s0, \s-1BUS\s0, or
\&\s-1SEGV\s0 signals arrive.  (But see the mention of signals in \s-1BUGS\s0 below.)
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To disable this default safe mode, set these values to something higher
than 0.  At a level of 1, you get backtraces upon receiving any kind
of warning (this is often annoying) or exception (this is
often valuable).  Unfortunately, the debugger cannot discern fatal
exceptions from non-fatal ones.  If \f(CW\*(C`dieLevel\*(C'\fR is even 1, then your
non-fatal exceptions are also traced and unceremoniously altered if they
came from \f(CW\*(C`eval\*(Aqed\*(C'\fR strings or from any kind of \f(CW\*(C`eval\*(C'\fR within modules
you're attempting to load.  If \f(CW\*(C`dieLevel\*(C'\fR is 2, the debugger doesn't
care where they came from:  It usurps your exception handler and prints
out a trace, then modifies all exceptions with its own embellishments.
This may perhaps be useful for some tracing purposes, but tends to hopelessly
destroy any program that takes its exception handling seriously.
.ie n .IP """AutoTrace""" 12
.el .IP "\f(CWAutoTrace\fR" 12
.IX Xref "debugger option, AutoTrace"
.IX Item "AutoTrace"
Trace mode (similar to \f(CW\*(C`t\*(C'\fR command, but can be put into
\&\f(CW\*(C`PERLDB_OPTS\*(C'\fR).
.ie n .IP """LineInfo""" 12
.el .IP "\f(CWLineInfo\fR" 12
.IX Xref "debugger option, LineInfo"
.IX Item "LineInfo"
File or pipe to print line number info to.  If it is a pipe (say,
\&\f(CW\*(C`|visual_perl_db\*(C'\fR), then a short message is used.  This is the
mechanism used to interact with a slave editor or visual debugger,
such as the special \f(CW\*(C`vi\*(C'\fR or \f(CW\*(C`emacs\*(C'\fR hooks, or the \f(CW\*(C`ddd\*(C'\fR graphical
debugger.
.ie n .IP """inhibit_exit""" 12
.el .IP "\f(CWinhibit_exit\fR" 12
.IX Xref "debugger option, inhibit_exit"
.IX Item "inhibit_exit"
If 0, allows \fIstepping off\fR the end of the script.
.ie n .IP """PrintRet""" 12
.el .IP "\f(CWPrintRet\fR" 12
.IX Xref "debugger option, PrintRet"
.IX Item "PrintRet"
Print return value after \f(CW\*(C`r\*(C'\fR command if set (default).
.ie n .IP """ornaments""" 12
.el .IP "\f(CWornaments\fR" 12
.IX Xref "debugger option, ornaments"
.IX Item "ornaments"
Affects screen appearance of the command line (see Term::ReadLine).
There is currently no way to disable these, which can render
some output illegible on some displays, or with some pagers.
This is considered a bug.
.ie n .IP """frame""" 12
.el .IP "\f(CWframe\fR" 12
.IX Xref "debugger option, frame"
.IX Item "frame"
Affects the printing of messages upon entry and exit from subroutines.  If
\&\f(CW\*(C`frame & 2\*(C'\fR is false, messages are printed on entry only. (Printing
on exit might be useful if interspersed with other messages.)
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If \f(CW\*(C`frame & 4\*(C'\fR, arguments to functions are printed, plus context
and caller info.  If \f(CW\*(C`frame & 8\*(C'\fR, overloaded \f(CW\*(C`stringify\*(C'\fR and
\&\f(CW\*(C`tie\*(C'\fRd \f(CW\*(C`FETCH\*(C'\fR is enabled on the printed arguments.  If \f(CW\*(C`frame
& 16\*(C'\fR, the return value from the subroutine is printed.
.Sp
The length at which the argument list is truncated is governed by the
next option:
.ie n .IP """maxTraceLen""" 12
.el .IP "\f(CWmaxTraceLen\fR" 12
.IX Xref "debugger option, maxTraceLen"
.IX Item "maxTraceLen"
Length to truncate the argument list when the \f(CW\*(C`frame\*(C'\fR option's
bit 4 is set.
.ie n .IP """windowSize""" 12
.el .IP "\f(CWwindowSize\fR" 12
.IX Xref "debugger option, windowSize"
.IX Item "windowSize"
Change the size of code list window (default is 10 lines).
.PP
The following options affect what happens with \f(CW\*(C`V\*(C'\fR, \f(CW\*(C`X\*(C'\fR, and \f(CW\*(C`x\*(C'\fR
commands:
.ie n .IP """arrayDepth""\fR, \f(CW""hashDepth""" 12
.el .IP "\f(CWarrayDepth\fR, \f(CWhashDepth\fR" 12
.IX Xref "debugger option, arrayDepth debugger option, hashDepth"
.IX Item "arrayDepth, hashDepth"
Print only first N elements ('' for all).
.ie n .IP """dumpDepth""" 12
.el .IP "\f(CWdumpDepth\fR" 12
.IX Xref "debugger option, dumpDepth"
.IX Item "dumpDepth"
Limit recursion depth to N levels when dumping structures.
Negative values are interpreted as infinity.  Default: infinity.
.ie n .IP """compactDump""\fR, \f(CW""veryCompact""" 12
.el .IP "\f(CWcompactDump\fR, \f(CWveryCompact\fR" 12
.IX Xref "debugger option, compactDump debugger option, veryCompact"
.IX Item "compactDump, veryCompact"
Change the style of array and hash output.  If \f(CW\*(C`compactDump\*(C'\fR, short array
may be printed on one line.
.ie n .IP """globPrint""" 12
.el .IP "\f(CWglobPrint\fR" 12
.IX Xref "debugger option, globPrint"
.IX Item "globPrint"
Whether to print contents of globs.
.ie n .IP """DumpDBFiles""" 12
.el .IP "\f(CWDumpDBFiles\fR" 12
.IX Xref "debugger option, DumpDBFiles"
.IX Item "DumpDBFiles"
Dump arrays holding debugged files.
.ie n .IP """DumpPackages""" 12
.el .IP "\f(CWDumpPackages\fR" 12
.IX Xref "debugger option, DumpPackages"
.IX Item "DumpPackages"
Dump symbol tables of packages.
.ie n .IP """DumpReused""" 12
.el .IP "\f(CWDumpReused\fR" 12
.IX Xref "debugger option, DumpReused"
.IX Item "DumpReused"
Dump contents of \*(L"reused\*(R" addresses.
.ie n .IP """quote""\fR, \f(CW""HighBit""\fR, \f(CW""undefPrint""" 12
.el .IP "\f(CWquote\fR, \f(CWHighBit\fR, \f(CWundefPrint\fR" 12
.IX Xref "debugger option, quote debugger option, HighBit debugger option, undefPrint"
.IX Item "quote, HighBit, undefPrint"
Change the style of string dump.  The default value for \f(CW\*(C`quote\*(C'\fR
is \f(CW\*(C`auto\*(C'\fR; one can enable double-quotish or single-quotish format
by setting it to \f(CW\*(C`"\*(C'\fR or \f(CW\*(C`\*(Aq\*(C'\fR, respectively.  By default, characters
with their high bit set are printed verbatim.
.ie n .IP """UsageOnly""" 12
.el .IP "\f(CWUsageOnly\fR" 12
.IX Xref "debugger option, UsageOnly"
.IX Item "UsageOnly"
Rudimentary per-package memory usage dump.  Calculates total
size of strings found in variables in the package.  This does not
include lexicals in a module's file scope, or lost in closures.
.PP
After the rc file is read, the debugger reads the \f(CW$ENV{PERLDB_OPTS}\fR
environment variable and parses this as the remainder of a \*(L"O ...\*(R"
line as one might enter at the debugger prompt.  You may place the
initialization options \f(CW\*(C`TTY\*(C'\fR, \f(CW\*(C`noTTY\*(C'\fR, \f(CW\*(C`ReadLine\*(C'\fR, and \f(CW\*(C`NonStop\*(C'\fR
there.
.PP
If your rc file contains:
.PP
.Vb 1
\&  parse_options("NonStop=1 LineInfo=db.out AutoTrace");
.Ve
.PP
then your script will run without human intervention, putting trace
information into the file \fIdb.out\fR.  (If you interrupt it, you'd
better reset \f(CW\*(C`LineInfo\*(C'\fR to \fI/dev/tty\fR if you expect to see anything.)
.ie n .IP """TTY""" 12
.el .IP "\f(CWTTY\fR" 12
.IX Xref "debugger option, TTY"
.IX Item "TTY"
The \s-1TTY\s0 to use for debugging I/O.
.ie n .IP """noTTY""" 12
.el .IP "\f(CWnoTTY\fR" 12
.IX Xref "debugger option, noTTY"
.IX Item "noTTY"
If set, the debugger goes into \f(CW\*(C`NonStop\*(C'\fR mode and will not connect to a \s-1TTY\s0.  If
interrupted (or if control goes to the debugger via explicit setting of
\&\f(CW$DB::signal\fR or \f(CW$DB::single\fR from the Perl script), it connects to a \s-1TTY\s0
specified in the \f(CW\*(C`TTY\*(C'\fR option at startup, or to a tty found at
runtime using the \f(CW\*(C`Term::Rendezvous\*(C'\fR module of your choice.
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This module should implement a method named \f(CW\*(C`new\*(C'\fR that returns an object
with two methods: \f(CW\*(C`IN\*(C'\fR and \f(CW\*(C`OUT\*(C'\fR.  These should return filehandles to use
for debugging input and output correspondingly.  The \f(CW\*(C`new\*(C'\fR method should
inspect an argument containing the value of \f(CW$ENV{PERLDB_NOTTY}\fR at
startup, or \f(CW"$ENV{HOME}/.perldbtty$$"\fR otherwise.  This file is not
inspected for proper ownership, so security hazards are theoretically
possible.
.ie n .IP """ReadLine""" 12
.el .IP "\f(CWReadLine\fR" 12
.IX Xref "debugger option, ReadLine"
.IX Item "ReadLine"
If false, readline support in the debugger is disabled in order
to debug applications that themselves use ReadLine.
.ie n .IP """NonStop""" 12
.el .IP "\f(CWNonStop\fR" 12
.IX Xref "debugger option, NonStop"
.IX Item "NonStop"
If set, the debugger goes into non-interactive mode until interrupted, or
programmatically by setting \f(CW$DB::signal\fR or \f(CW$DB::single\fR.
.PP
Here's an example of using the \f(CW$ENV{PERLDB_OPTS}\fR variable:
.PP
.Vb 1
\&    $ PERLDB_OPTS="NonStop frame=2" perl \-d myprogram
.Ve
.PP
That will run the script \fBmyprogram\fR without human intervention,
printing out the call tree with entry and exit points.  Note that
\&\f(CW\*(C`NonStop=1 frame=2\*(C'\fR is equivalent to \f(CW\*(C`N f=2\*(C'\fR, and that originally,
options could be uniquely abbreviated by the first letter (modulo
the \f(CW\*(C`Dump*\*(C'\fR options).  It is nevertheless recommended that you
always spell them out in full for legibility and future compatibility.
.PP
Other examples include
.PP
.Vb 1
\&    $ PERLDB_OPTS="NonStop LineInfo=listing frame=2" perl \-d myprogram
.Ve
.PP
which runs script non-interactively, printing info on each entry
into a subroutine and each executed line into the file named \fIlisting\fR.
(If you interrupt it, you would better reset \f(CW\*(C`LineInfo\*(C'\fR to something
\&\*(L"interactive\*(R"!)
.PP
Other examples include (using standard shell syntax to show environment
variable settings):
.PP
.Vb 2
\&  $ ( PERLDB_OPTS="NonStop frame=1 AutoTrace LineInfo=tperl.out"
\&      perl \-d myprogram )
.Ve
.PP
which may be useful for debugging a program that uses \f(CW\*(C`Term::ReadLine\*(C'\fR
itself.  Do not forget to detach your shell from the \s-1TTY\s0 in the window that
corresponds to \fI/dev/ttyXX\fR, say, by issuing a command like
.PP
.Vb 1
\&  $ sleep 1000000
.Ve
.PP