The document discusses using Perl on the command line. It provides examples of using one-liners with flags like -e, -p, and -n to manipulate or filter data without writing scripts. Specific applications demonstrated include parsing log files, sorting/counting words, and solving word puzzles by manipulating strings. The document emphasizes how Perl on the command line allows ad hoc data munging and analysis tasks in just a few lines of code.

1. Command-line Perl 1
Command-line Perl
or: Perl one-liners saved my career
or: `perldoc perlrun` brought to life
or: Data Munging on PowerThirst
(YAPC::NA::2009)
Bruce Gray (Util)
Any sufficiently advanced technology...
... will fail when used for even more advanced tasks.
If you are viewing a printed version of this presentation, or seeing it on SlideShare, it probably looks awful.
Instead, please get a packaged copy of the HTML version by emailing me (bruce.gray@acm.org), or downloading from:
http://feather.perl6.nl/~util/
It should look great in Firefox, or even better in Opera's "Presentation Mode" (fullscreen).
Larry == Comedic One-liners
You want it in one line? Does it have to fit in 80 columns? :-)
--Larry Wall in <7349@jpl-devvax.JPL.NASA.GOV>
Perl code on the command line
Look Ma, no script!
$ perl print
Can't open perl script "print": No such file or directory
-e (The `e` is for hysterical raisins)
$ perl -e print
(No output)
Quoting on the command line
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

2. Command-line Perl 2
Quoting on the command line
...and you can quote me on that
$ perl -e ' print "Hellon" ' # Unix
$ perl -e " print 'Hello' . $/ " # Win32
$ perl -e " print qq'Hellon' " # Win32; sick
$ perl -e " print qq{Hellon} " # Win32; better
Automatic end-of-line handling
Computing the meaning of 2 lives. `bc` not found
$ perl -e ' print 42 * 42 '
1764$ perl -e ' print 42 * 42 * 42 '
74088$
Automatic end-of-line handling
The -l flag adds "n" to `print`
$ perl -le ' print 42 * 42 '
1764
$ perl -le ' print 42 * 42 * 42 '
74088
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

3. Command-line Perl 3
Unconventional conventionists
The code formerly known as:
$ perl -e ' print "Hellon"; '
with output:
Hello
will now appear as:
$ perl -e '...' any arguments here
print "Hellon";
Hello
Defaults
@ARGV is the array of command-line arguments.
shift takes @ARGV as its default.
$ perl -le '...' foo bar baz
print @ARGV; $z=shift; print $z;
foobarbaz
foo
Defaults
print takes $_ as default, and for sets $_ as default.
$ perl -le '...' foo bar baz
print for @ARGV
foo
bar
baz
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

4. Command-line Perl 4
Warnings
Double your money!
$ perl -le '...' 15
$zz = shift; print $z . $z
(No output)
Warnings
Always pay for the cheap insurance
$ perl -wle '...' 15
$zz = shift; print $z . $z
Name "main::zz" used only once: possible typo...
Use of uninitialized value in concatenation...
Use of uninitialized value in concatenation...
Corrected
$ perl -wle '...' 15
$z = shift; print $z . $z
1515
Command-line Modules
-M means `use`
$ perl -MData::Dumper -wle 1
(No output)
$ perl -MData::Dumper::Dear::John-wle 1
Can't locate Data/Dumper/Dear/John.pm in @INC
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

5. Command-line Perl 5
Command-line Modules
$FOO::VERSION is a CPAN standard
$ perl -MData::Dumper -wle '...'
print $Data::Dumper::VERSION;
2.121_02
Cross Words
Capital of Portugal, 6 letters, ? i ? b o ?
$ perl -wlne '...' /usr/share/dict/words
print if /^[A-Z]i.bo.$/
Lisbon
Hi, Cog!
PHP
Scrambled word: ulsacepoer
$ perl -wlne '...' /usr/share/dict/words | wc
print if /^[ulsacpeeor]{10}$/
104
PHP
Scrambled word: ulsacepoer
$ perl -wlne '...' /usr/share/dict/words
print if join("", sort split "") eq "aceeloprsu"
perlaceous
Per*la"ceous, a. [See Pearl.] Pearly; resembling pearl.
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

6. Command-line Perl 6
Dizzy Camels
Scrambling word: perlaceous
$ perl -MList::Util=shuffle -wle '...' perlaceous
@z = split "", shift; print join "", shuffle @z;
ulsacepoer
Prized Doors
$ perl -MList::Util=shuffle -wle '...' 27
@z = 1 .. shift; print for (shuffle @z)[0..9];
perl -MList::Util=shuffle -wle '@z = 1 .. shift ; print for (shuffle @z)[0..9];'
Coke?
Don't run this just for this talk! Download svn.log.gz !
$ svn -q log https://svn.parrot.org/parrot/ > svn.log
-------------------------------------------------------------------
r39696 | petdance | 2009-06-21 23:12:08 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39695 | japhb | 2009-06-21 23:10:39 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39694 | cotto | 2009-06-21 21:49:35 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39693 | japhb | 2009-06-21 21:23:28 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39692 | moritz | 2009-06-21 17:08:28 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39691 | japhb | 2009-06-21 13:03:24 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39690 | coke | 2009-06-21 12:50:53 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39689 | japhb | 2009-06-21 12:36:39 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39688 | cotto | 2009-06-21 10:42:11 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39687 | bacek | 2009-06-21 06:24:16 -0500 (Sun, 21 Jun 2009)
-------------------------------------------------------------------
r39686 | whiteknight | 2009-06-21 05:44:46 -0500 (Sun, 21 Jun 2009)
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

7. Command-line Perl 7
10 GOTO 10
-p reads a line, runs your code, prints a line.
$ perl -wlpe '...' svn.log
$_ = uc;
----------------------------------------------------------------
R39696 | PETDANCE | 2009-06-21 23:12:08 -0500 (SUN, 21 JUN 2009)
----------------------------------------------------------------
R39695 | JAPHB | 2009-06-21 23:10:39 -0500 (SUN, 21 JUN 2009)
----------------------------------------------------------------
R39694 | COTTO | 2009-06-21 21:49:35 -0500 (SUN, 21 JUN 2009)
----------------------------------------------------------------
R39693 | JAPHB | 2009-06-21 21:23:28 -0500 (SUN, 21 JUN 2009)
----------------------------------------------------------------
R39692 | MORITZ | 2009-06-21 17:08:28 -0500 (SUN, 21 JUN 2009)
10 GOTO 10
-n reads a line, runs your code.
$ perl -wlne '...' svn.log
next if /---/; $_ = uc; print;
R39696 | PETDANCE | 2009-06-21 23:12:08 -0500 (SUN, 21 JUN 2009)
R39695 | JAPHB | 2009-06-21 23:10:39 -0500 (SUN, 21 JUN 2009)
R39694 | COTTO | 2009-06-21 21:49:35 -0500 (SUN, 21 JUN 2009)
R39693 | JAPHB | 2009-06-21 21:23:28 -0500 (SUN, 21 JUN 2009)
R39692 | MORITZ | 2009-06-21 17:08:28 -0500 (SUN, 21 JUN 2009)
R39691 | JAPHB | 2009-06-21 13:03:24 -0500 (SUN, 21 JUN 2009)
R39690 | COKE | 2009-06-21 12:50:53 -0500 (SUN, 21 JUN 2009)
R39689 | JAPHB | 2009-06-21 12:36:39 -0500 (SUN, 21 JUN 2009)
R39688 | COTTO | 2009-06-21 10:42:11 -0500 (SUN, 21 JUN 2009)
R39687 | BACEK | 2009-06-21 06:24:16 -0500 (SUN, 21 JUN 2009)
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

8. Command-line Perl 8
HITBULLS
$ perl -MO=Deparse -ne ' next if /---/; $_ = uc; print; '
LINE: while (defined($_ = <ARGV>)) {
next if /---/;
$_ = uc $_;
print $_;
}
$ perl -MO=Deparse -pe ' $_ = uc; '
LINE: while (defined($_ = <ARGV>)) {
$_ = uc $_;
}
continue {
die "-p destination: $!n" unless print $_;
}
Home on the Range
$ perl -ne '...' svn.log
print if /^r39688/ .. /^r39686/;
r39688 | cotto | 2009-06-21 10:42:11 -0500 (Sun, 21 Jun 2009)
------------------------------------------------------------------------
r39687 | bacek | 2009-06-21 06:24:16 -0500 (Sun, 21 Jun 2009)
------------------------------------------------------------------------
r39686 | whiteknight | 2009-06-21 05:44:46 -0500 (Sun, 21 Jun 2009)
print if ($. == 2) .. ($. == 4);
print if 2 .. 4;
r39696 | petdance | 2009-06-21 23:12:08 -0500 (Sun, 21 Jun 2009)
------------------------------------------------------------------------
r39695 | japhb | 2009-06-21 23:10:39 -0500 (Sun, 21 Jun 2009)
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

9. Command-line Perl 9
Laughing Buddha, Frowning PerlMonk
XKCD w/o EDVO
$ ls XKCD_mirror/xkcd*.html | tail -2
XKCD_mirror/xkcd0539.html
XKCD_mirror/xkcd0540.html
$ perl -wlne '...' XKCD_mirror/xkcd*.html
push @L, $_ if not $h{$_}++;
END{ printf "%7dt%sn", $h{$_}, $_ for @L }
Laughing Buddha, Frowning PerlMonk
...
539 <div id="contentContainer">
539 <div id="middleContent" class="dialog">
1 <h1>Barrel - Part 1</h1><br/>
1617 <br />
1078 <div class="menuCont">
1078 <ul>
1078 <li><a href="/1/">|&lt;</a></li>
2 <li><a href="#" accesskey="p">&lt; Prev</a></li>
539 <li><a href="http://dynamic.xkcd.com/comic/random/" id="rnd_btn_t">Random</a></li>
2 <li><a href="/2/" accesskey="n">Next &gt;</a></li>
1078 <li><a href="/">&gt;|</a></li>
1078 </ul>
2156 </div>
1617 <br/>
1 <img src="http://imgs.xkcd.com/comics/barrel_cropped_(1).jpg" title="Don't we all." alt="Barrel - Part 1" /><br/
>
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

10. Command-line Perl 10
Awk
$ perl -wlane '...' svn.log
print $F[0];
-------------------------------------
r39696
-------------------------------------
r39695
-------------------------------------
r39694
Old McDonald had a farm...
$ perl -wlnae '...' svn.log
{FAIL}
Respect My Authoritay
$ cut -s -d ' ' -f 3 svn.log | tr "[:upper:]" "[:lower:]" | sort | uniq -c | sort -nr
$ perl -wlane '...' svn.log
$h{ lc $F[2] }++ if @F>1;
END{ printf "%7dt%sn", $h{$_}, $_ for sort { $h{$b} <=> $h{$a} } keys %h }
4215 leo
3008 coke
2850 bernhard
2669 jkeenan
2408 pmichaud
1975 chromatic
1814 allison
You have to believe we are magic...
$ perl -MY -wlane '...' svn.log
$h{ lc $F[2] }++ if @F>1; END{ dhn }
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM

11. Command-line Perl 11
And the hits keep coming
-i -i.bak -0 -00 -0777 -E -l[octnum -m -C PERLIO
]
$ perldoc perlrun
$ perldoc perlvar
http://perldoc.perl.org/perlrun.html
http://perldoc.perl.org/perlvar.html
Golf
file://localhost/YAPC_Talk/index.html June 22, 2009 3:25:46 PM