brennen
/
presentations

<!DOCTYPE html><html lang=en><head>  <meta charset="utf-8">  <title>perl</title>  <link rel=stylesheet href="slides.css" />  <link rel="alternate" type="application/atom+xml" title="changes" href="//p1k3.com/userland-book/feed.xml" />  <link rel="stylesheet" href="js/styles/sunburst.css">  <script src="js/highlight.pack.js"></script>  <script src="js/jquery.js" type="text/javascript"></script>  <script>hljs.initHighlightingOnLoad();</script></head>
<body>
<section>
<p style="font-size: 3em; margin-bottom: 0; text-align: center;">  All the Perl you need</p>
<p style="font-size: 2em; text-align: center;">  for slicing and dicing text files</p>
<p style="text-align: center;">  Brennen Bearnes &lt;bbearnes@wikimedia.org&gt;</p>
<p style="text-align: center;"><small>  Source:  <a href="https://code.p1k3.com/gitea/brennen/wmf-engprod-offsite-slides">    code.p1k3.com/gitea/brennen/wmf-engprod-offsite-slides  </a><br />
  Slides:  <a href="https://squiggle.city/~brennen/perl/">    squiggle.city/~brennen/perl/  </a></small></p>
</section><section>

<h2><a name=Agenda href=#Agenda></a> Agenda</h2>
<ol><li> A capsule history</li><li> What is Perl actually like?</li><li> Basic syntax and techniques</li><li> Examples</li></ol>

</section>

<section>

<h2><a name=A-capsule-history href=#A-capsule-history></a> A capsule history</h2>
<ul><li>1987 - Started by Larry Wall</li><li>1991 - <em>Programming Perl</em> - the Camel Book</li><li>1994-95 -  Perl 5, CPAN</li><li>late 1990s - Perl CGI unerpins much of the web</li><li>2000ish - Massive derail into Perl 6 development</li></ul>

</section>

<section>

<h2><a name=What-rsquo-s-Perl-actually-like href=#What-rsquo-s-Perl-actually-like></a> What&rsquo;s Perl actually like?</h2>
<ul><li>Backronym: &ldquo;Practical Extraction and Report Language&rdquo;.</li><li>&ldquo;There&rsquo;s more than one way to do it&rdquo;</li><li>&ldquo;Executable line-noise&rdquo;</li><li><a href="https://lobste.rs/s/odi5eu/93_paint_splatters_are_valid_perl">&ldquo;93% of Paint Splatters are Valid Perl Programs&rdquo;</a></li></ul>

</section>

<section>

<h2><a name=What-rsquo-s-Perl-actually-like href=#What-rsquo-s-Perl-actually-like></a> What&rsquo;s Perl actually like?</h2>
<p>A general-purpose, multi-paradigm programming language.</p>
<p>That also has a lot in common with the Unix shell.</p>
</section>

<section>

<h2><a name=What-rsquo-s-Perl-actually-like href=#What-rsquo-s-Perl-actually-like></a> What&rsquo;s Perl actually like?</h2>
<p>General-purpose, multi-paradigm programming language.</p>
<p>That also has a lot in common with the Unix shell.</p>
<p>So: <strong>A widely-installed environment where you can combine small tools to workwith data.</strong></p>
</section>

<section>

<p>A sample data file, tab-separated names of some authors:</p>
<!-- exec -->

<pre><code>$ column -t examples/authors.tsvRobinson  EdenWaring    Gwendolyn  L.Brunner   JohnTolkien   John       Ronald  ReuelWalton    JoToews     MiriamCadigan   PatLe        Guin       Ursula  K.Veselka   VanessaWells     MarthaLeckie    Ann</code></pre>
<!-- end -->

</section>

<section>

<p>Perl is often described as a superset of <code>grep</code>, <code>sed</code>, and <code>awk</code>.</p>
<p>Combines filtering, sorting, and transforming strings with stuff that&rsquo;s hard(or missing) in Bash:</p>
<ul><li>Functions</li><li>Clean basic data structures</li><li>Robust quoting</li><li>Sensible control structures</li><li>Variable scope</li></ul>

</section>

<section>

<p>Like <code>grep</code>:</p>
<!-- exec -->

<pre><code>$ perl -ne 'print if m/^T/;' examples/authors.tsv | column -tTolkien  John    Ronald  ReuelToews    Miriam</code></pre>
<!-- end -->

</section>

<section>

<p>Like <code>cut</code> or <code>awk</code>:</p>
<!-- exec -->

<pre><code>$ perl -anE 'say @F[1];' examples/authors.tsvEdenGwendolynJohnJohnJoMiriamPatGuinVanessaMarthaAnn</code></pre>
<!-- end -->

</section>

<section>

<p>Like <code>sed</code> or <code>tr</code>:</p>
<!-- exec -->

<pre><code>$ perl -pe 'tr/[a-z]/[A-Z]/' examples/authors.tsv | column -tROBINSON  EDENWARING    GWENDOLYN  L.BRUNNER   JOHNTOLKIEN   JOHN       RONALD  REUELWALTON    JOTOEWS     MIRIAMCADIGAN   PATLE        GUIN       URSULA  K.VESELKA   VANESSAWELLS     MARTHALECKIE    ANN</code></pre>
<!-- end -->

</section>

<section>

<p>I&rsquo;m not here to convince you to write large programs in Perl.</p>
<p>I want to gesture at a portion of the language useful for:</p>
<ul><li>One-liners</li><li>Short utility scripts</li><li>Exploratory data work &amp; transforms</li></ul>

<p>Let&rsquo;s go over some basic syntax and techniques, and then look at a fewexamples from my toolkit.</p>
</section>

<section>

<h2><a name=Basics href=#Basics></a> Basics</h2>
<ul><li>There&rsquo;s a <em>lot</em> of syntax</li><li>Much of it recognizable from elsewhere:
<ul><li>PHP syntax is basically Perl-lite</li><li>Perl regexps: <code>grep</code>, <code>sed</code>, <code>vi</code>, PCRE, etc.</li><li>Idioms from the shell, C, and even BASIC</li></ul></li></ul>

</section>

<section>

<h2><a name=Basics href=#Basics></a> Basics</h2>
<!-- exec-raw cat examples/hello.pl -->

<pre><code>#!/usr/bin/env perl
print "Hello EngProd.\n";</code></pre>
<!-- end -->


<!-- exec -->

<pre><code>$ ./examples/hello.plHello EngProd.</code></pre>
<!-- end -->

</section>

<section>

<h2><a name=Basics-boilerplate-edition href=#Basics-boilerplate-edition></a> Basics - boilerplate edition</h2>
<!-- exec-raw cat examples/hello_boilerplate.pl -->

<pre><code>#!/usr/bin/env perl
use warnings;use strict;use 5.10.0;
say greet($ARGV[0]);
sub greet {  my ($greetee) = @_;  return "Hello $greetee.";}</code></pre>
<!-- end -->


<!-- exec -->

<pre><code>$ ./examples/hello_boilerplate.pl 'EngProd'Hello EngProd.</code></pre>
<!-- end -->

</section>

<section>

<h2><a name=A-basic-filter href=#A-basic-filter></a> A basic filter</h2>
<!-- exec-raw cat examples/filter_authors.pl -->

<pre><code>#!/usr/bin/env perl
use warnings;use strict;use 5.10.0;
# Extract name where given name matches "John":while (&lt;&gt;) {  say "$2 $1" if m/^(.*)\t(Jo.*?)(\t|$)/i;}</code></pre>
<!-- end -->


<!-- exec -->

<pre><code>$ ./examples/filter_authors.pl examples/authors.tsvJohn BrunnerJohn TolkienJo Walton</code></pre>
<!-- end -->

</section>
<script>$(document).ready(function () {  // ☜ ☝ ☞ ☟ ☆ ✠ ✡ ✢ ✣ ✤ ✥ ✦ ✧ ✩ ✪ 
  // get all the "slides", hide them  $sections = $('section');  $sections.hide();
  var section_number = 0;  var $cur_section = $( $sections.get(section_number) );  $cur_section.toggle(); // show first slide
  var transit = function (jump) {    $('button').hide();    $cur_section.hide();    section_number += jump;    if (section_number > ($sections.length - 1)) {      section_number = 0;    }    $cur_section = $( $sections.get(section_number) );    $cur_section.toggle({      duration: 200,      done: function () { $('button').show(); }    });  };
  var $fwd_button = $('<button class=clicker-button>next</button>');  var $bwd_button = $('<button class=clicker-button>prev</button>');
  $fwd_button.click(function (e) {    e.preventDefault();    transit(1);  });  $bwd_button.click(function (e) {    e.preventDefault();    transit(-1);  });
  $(document).keydown(function(e) {    switch(e.which) {      case 8:  // backspace      case 37: // left        $bwd_button.click();        break;      case 32: // spacebar      case 39: // right        $fwd_button.click();        break;      case 90:        toggleFullScreen();        break;      default:        return;    }    e.preventDefault();  });
  $button_group = $('<div class=buttons/>');  $button_group.append($bwd_button);  $button_group.append($fwd_button);  $('body').append($button_group);
  var toggleFullScreen = function () {    if (!document.fullscreenElement &&    // alternative standard method        !document.mozFullScreenElement && !document.webkitFullscreenElement && !document.msFullscreenElement ) {  // current working methods      if (document.documentElement.requestFullscreen) {        document.documentElement.requestFullscreen();      } else if (document.documentElement.msRequestFullscreen) {        document.documentElement.msRequestFullscreen();      } else if (document.documentElement.mozRequestFullScreen) {        document.documentElement.mozRequestFullScreen();      } else if (document.documentElement.webkitRequestFullscreen) {        document.documentElement.webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);      }    } else {      if (document.exitFullscreen) {        document.exitFullscreen();      } else if (document.msExitFullscreen) {        document.msExitFullscreen();      } else if (document.mozCancelFullScreen) {        document.mozCancelFullScreen();      } else if (document.webkitExitFullscreen) {        document.webkitExitFullscreen();      }    }  };
});</script></body></html>