diff options
Diffstat (limited to 'pod/perldebtut.pod')
| -rw-r--r-- | pod/perldebtut.pod | 226 |
1 files changed, 120 insertions, 106 deletions
diff --git a/pod/perldebtut.pod b/pod/perldebtut.pod index cc4f5051e1..2558ed27f9 100644 --- a/pod/perldebtut.pod +++ b/pod/perldebtut.pod @@ -154,26 +154,40 @@ DB<1>h List/search source lines: Control script execution: l [ln|sub] List source code T Stack trace - - or . List previous/current line s [expr] Single step [in expr] - v [line] View around line n [expr] Next, steps over subs + - or . List previous/current line s [expr] Single step + [in expr] + v [line] View around line n [expr] Next, steps over + subs f filename View source in file <CR/Enter> Repeat last n or s - /pattern/ ?patt? Search forw/backw r Return from subroutine - M Show module versions c [ln|sub] Continue until position - Debugger controls: L List break/watch/actions - o [...] Set debugger options t [expr] Toggle trace [trace expr] - <[<]|{[{]|>[>] [cmd] Do pre/post-prompt b [ln|event|sub] [cnd] Set breakpoint - ! [N|pat] Redo a previous command B ln|* Delete a/all breakpoints + /pattern/ ?patt? Search forw/backw r Return from + subroutine + M Show module versions c [ln|sub] Continue until + position + Debugger controls: L List break/watch/ + actions + o [...] Set debugger options t [expr] Toggle trace + [trace expr] + <[<]|{[{]|>[>] [cmd] Do pre/post-prompt b [ln|event|sub] [cnd] Set + breakpoint + ! [N|pat] Redo a previous command B ln|* Delete a/all + breakpoints H [-num] Display last num commands a [ln] cmd Do cmd before line - = [a val] Define/list an alias A ln|* Delete a/all actions - h [db_cmd] Get help on command w expr Add a watch expression - h h Complete help page W expr|* Delete a/all watch exprs - |[|]db_cmd Send output to pager ![!] syscmd Run cmd in a subprocess + = [a val] Define/list an alias A ln|* Delete a/all + actions + h [db_cmd] Get help on command w expr Add a watch + expression + h h Complete help page W expr|* Delete a/all watch + exprs + |[|]db_cmd Send output to pager ![!] syscmd Run cmd in a + subprocess q or ^D Quit R Attempt a restart Data Examination: expr Execute perl code, also see: s,n,t expr - x|m expr Evals expr in list context, dumps the result or lists methods. + x|m expr Evals expr in list context, dumps the result or lists + methods. p expr Print expression (uses script's current package). S [[!]pat] List subroutine names [not] matching pattern - V [Pk [Vars]] List Variables in Package. Vars can be ~pattern or !pattern. + V [Pk [Vars]] List Variables in Package. Vars can be ~pattern or + !pattern. X [Vars] Same as "V current_package [Vars]". y [n [Vars]] List lexicals in higher scope <n>. Vars same as V. For more help, type h cmd_letter, or run man perldebug for all docs. @@ -335,25 +349,25 @@ Let's make a quick object and x-plode it, first we'll start the debugger: it wants some form of input from STDIN, so we give it something non-committal, a zero: - > perl -de 0 - Default die handler restored. + > perl -de 0 + Default die handler restored. - Loading DB routines from perl5db.pl version 1.07 - Editor support available. + Loading DB routines from perl5db.pl version 1.07 + Editor support available. - Enter h or `h h' for help, or `man perldebug' for more help. + Enter h or `h h' for help, or `man perldebug' for more help. - main::(-e:1): 0 + main::(-e:1): 0 Now build an on-the-fly object over a couple of lines (note the backslash): - DB<1> $obj = bless({'unique_id'=>'123', 'attr'=> \ - cont: {'col' => 'black', 'things' => [qw(this that etc)]}}, 'MY_class') + DB<1> $obj = bless({'unique_id'=>'123', 'attr'=> \ + cont: {'col' => 'black', 'things' => [qw(this that etc)]}}, 'MY_class') And let's have a look at it: DB<2> x $obj - 0 MY_class=HASH(0x828ad98) + 0 MY_class=HASH(0x828ad98) 'attr' => HASH(0x828ad68) 'col' => 'black' 'things' => ARRAY(0x828abb8) @@ -366,38 +380,38 @@ And let's have a look at it: Useful, huh? You can eval nearly anything in there, and experiment with bits of code or regexes until the cows come home: - DB<3> @data = qw(this that the other atheism leather theory scythe) + DB<3> @data = qw(this that the other atheism leather theory scythe) - DB<4> p 'saw -> '.($cnt += map { print "\t:\t$_\n" } grep(/the/, sort @data)) - atheism - leather - other - scythe - the - theory - saw -> 6 + DB<4> p 'saw -> '.($cnt += map { print "\t:\t$_\n" } grep(/the/, sort @data)) + atheism + leather + other + scythe + the + theory + saw -> 6 If you want to see the command History, type an 'B<H>': - DB<5> H - 4: p 'saw -> '.($cnt += map { print "\t:\t$_\n" } grep(/the/, sort @data)) - 3: @data = qw(this that the other atheism leather theory scythe) - 2: x $obj - 1: $obj = bless({'unique_id'=>'123', 'attr'=> - {'col' => 'black', 'things' => [qw(this that etc)]}}, 'MY_class') - DB<5> + DB<5> H + 4: p 'saw -> '.($cnt += map { print "\t:\t$_\n" } grep(/the/, sort @data)) + 3: @data = qw(this that the other atheism leather theory scythe) + 2: x $obj + 1: $obj = bless({'unique_id'=>'123', 'attr'=> + {'col' => 'black', 'things' => [qw(this that etc)]}}, 'MY_class') + DB<5> And if you want to repeat any previous command, use the exclamation: 'B<!>': - DB<5> !4 - p 'saw -> '.($cnt += map { print "$_\n" } grep(/the/, sort @data)) - atheism - leather - other - scythe - the - theory - saw -> 12 + DB<5> !4 + p 'saw -> '.($cnt += map { print "$_\n" } grep(/the/, sort @data)) + atheism + leather + other + scythe + the + theory + saw -> 12 For more on references see L<perlref> and L<perlreftut> @@ -407,50 +421,50 @@ For more on references see L<perlref> and L<perlreftut> Here's a simple program which converts between Celsius and Fahrenheit, it too has a problem: - #!/usr/bin/perl -w - use strict; - - my $arg = $ARGV[0] || '-c20'; - - if ($arg =~ /^\-(c|f)((\-|\+)*\d+(\.\d+)*)$/) { - my ($deg, $num) = ($1, $2); - my ($in, $out) = ($num, $num); - if ($deg eq 'c') { - $deg = 'f'; - $out = &c2f($num); - } else { - $deg = 'c'; - $out = &f2c($num); - } - $out = sprintf('%0.2f', $out); - $out =~ s/^((\-|\+)*\d+)\.0+$/$1/; - print "$out $deg\n"; - } else { - print "Usage: $0 -[c|f] num\n"; - } - exit; + #!/usr/bin/perl -w + use strict; - sub f2c { - my $f = shift; - my $c = 5 * $f - 32 / 9; - return $c; - } + my $arg = $ARGV[0] || '-c20'; - sub c2f { - my $c = shift; - my $f = 9 * $c / 5 + 32; - return $f; + if ($arg =~ /^\-(c|f)((\-|\+)*\d+(\.\d+)*)$/) { + my ($deg, $num) = ($1, $2); + my ($in, $out) = ($num, $num); + if ($deg eq 'c') { + $deg = 'f'; + $out = &c2f($num); + } else { + $deg = 'c'; + $out = &f2c($num); } + $out = sprintf('%0.2f', $out); + $out =~ s/^((\-|\+)*\d+)\.0+$/$1/; + print "$out $deg\n"; + } else { + print "Usage: $0 -[c|f] num\n"; + } + exit; + + sub f2c { + my $f = shift; + my $c = 5 * $f - 32 / 9; + return $c; + } + + sub c2f { + my $c = shift; + my $f = 9 * $c / 5 + 32; + return $f; + } For some reason, the Fahrenheit to Celsius conversion fails to return the expected output. This is what it does: - > temp -c0.72 - 33.30 f + > temp -c0.72 + 33.30 f - > temp -f33.3 - 162.94 c + > temp -f33.3 + 162.94 c Not very consistent! We'll set a breakpoint in the code manually and run it under the debugger to see what's going on. A breakpoint is a flag, to which @@ -600,28 +614,28 @@ Actions, watch variables, stack traces etc.: on the TODO list. Ever wanted to know what a regex looked like? You'll need perl compiled with the DEBUGGING flag for this one: - > perl -Dr -e '/^pe(a)*rl$/i' - Compiling REx `^pe(a)*rl$' - size 17 first at 2 - rarest char - at 0 - 1: BOL(2) - 2: EXACTF <pe>(4) - 4: CURLYN[1] {0,32767}(14) - 6: NOTHING(8) - 8: EXACTF <a>(0) - 12: WHILEM(0) - 13: NOTHING(14) - 14: EXACTF <rl>(16) - 16: EOL(17) - 17: END(0) - floating `'$ at 4..2147483647 (checking floating) stclass `EXACTF <pe>' -anchored(BOL) minlen 4 - Omitting $` $& $' support. - - EXECUTING... - - Freeing REx: `^pe(a)*rl$' + > perl -Dr -e '/^pe(a)*rl$/i' + Compiling REx `^pe(a)*rl$' + size 17 first at 2 + rarest char + at 0 + 1: BOL(2) + 2: EXACTF <pe>(4) + 4: CURLYN[1] {0,32767}(14) + 6: NOTHING(8) + 8: EXACTF <a>(0) + 12: WHILEM(0) + 13: NOTHING(14) + 14: EXACTF <rl>(16) + 16: EOL(17) + 17: END(0) + floating `'$ at 4..2147483647 (checking floating) stclass + `EXACTF <pe>' anchored(BOL) minlen 4 + Omitting $` $& $' support. + + EXECUTING... + + Freeing REx: `^pe(a)*rl$' Did you really want to know? :-) For more gory details on getting regular expressions to work, have a look at @@ -644,7 +658,7 @@ To watch the tail of a dynamically growing logfile, (from the command line): Wrapping all die calls in a handler routine can be useful to see how, and from where, they're being called, L<perlvar> has more information: - BEGIN { $SIG{__DIE__} = sub { require Carp; Carp::confess(@_) } } + BEGIN { $SIG{__DIE__} = sub { require Carp; Carp::confess(@_) } } Various useful techniques for the redirection of STDOUT and STDERR filehandles are explained in L<perlopentut> and L<perlfaq8>. |