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| author | johannst <johannst@users.noreply.github.com> | 2020-04-28 09:11:18 +0000 |
|---|---|---|
| committer | johannst <johannst@users.noreply.github.com> | 2020-04-28 09:11:18 +0000 |
| commit | 15230bbb9b1f69def9b0e1b41a097638c0fda734 (patch) | |
| tree | 2b490b2f0b8d6f3eab0af91c7ba5cc557b540af6 /misc/awk.html | |
| parent | ce1a0eaa58f7ad07c5389996a90c4b02bdf573fc (diff) | |
| download | notes-15230bbb9b1f69def9b0e1b41a097638c0fda734.tar.gz notes-15230bbb9b1f69def9b0e1b41a097638c0fda734.zip | |
deploy: fef4d6ff2ad9f48e6dccde0f061453e6a3ac624e
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| -rw-r--r-- | misc/awk.html | 334 |
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diff --git a/misc/awk.html b/misc/awk.html new file mode 100644 index 0000000..64c5531 --- /dev/null +++ b/misc/awk.html @@ -0,0 +1,334 @@ +<!DOCTYPE HTML> +<html lang="en" class="sidebar-visible no-js light"> + <head> + <!-- Book generated using mdBook --> + <meta charset="UTF-8"> + <title>awk - Notes</title> + + + <meta content="text/html; charset=utf-8" http-equiv="Content-Type"> + <meta name="description" content=""> + <meta name="viewport" content="width=device-width, initial-scale=1"> + <meta name="theme-color" content="#ffffff" /> + + <link rel="shortcut icon" href="../favicon.png"> + <link rel="stylesheet" href="../css/variables.css"> + <link rel="stylesheet" href="../css/general.css"> + <link rel="stylesheet" href="../css/chrome.css"> + <link rel="stylesheet" href="../css/print.css" media="print"> + + <!-- Fonts --> + <link rel="stylesheet" href="../FontAwesome/css/font-awesome.css"> + <link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css"> + <link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css"> + + <!-- Highlight.js Stylesheets --> + <link rel="stylesheet" href="../highlight.css"> + <link rel="stylesheet" href="../tomorrow-night.css"> + <link rel="stylesheet" href="../ayu-highlight.css"> + + <!-- Custom theme stylesheets --> + + + + </head> + <body> + <!-- Provide site root to javascript --> + <script type="text/javascript"> + var path_to_root = "../"; + var default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? 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aria-hidden="true">1.3.</strong> fish</a></li><li class="expanded "><a href="../misc/tmux.html"><strong aria-hidden="true">1.4.</strong> tmux</a></li><li class="expanded "><a href="../misc/git.html"><strong aria-hidden="true">1.5.</strong> git</a></li><li class="expanded "><a href="../misc/awk.html" class="active"><strong aria-hidden="true">1.6.</strong> awk</a></li><li class="expanded "><a href="../misc/emacs.html"><strong aria-hidden="true">1.7.</strong> emacs</a></li><li class="expanded "><a href="../misc/gdb.html"><strong aria-hidden="true">1.8.</strong> gdb</a></li><li class="expanded "><a href="../misc/radare2.html"><strong aria-hidden="true">1.9.</strong> radare2</a></li></ol></li><li class="expanded "><a href="../monitor/index.html"><strong aria-hidden="true">2.</strong> Resource analysis & monitor</a></li><li><ol class="section"><li class="expanded "><a href="../monitor/lsof.html"><strong aria-hidden="true">2.1.</strong> lsof</a></li><li class="expanded "><a 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aria-hidden="true">3.4.</strong> OProfile</a></li><li class="expanded "><a href="../trace_profile/time.html"><strong aria-hidden="true">3.5.</strong> time</a></li></ol></li><li class="expanded "><a href="../binary/index.html"><strong aria-hidden="true">4.</strong> Binary</a></li><li><ol class="section"><li class="expanded "><a href="../binary/od.html"><strong aria-hidden="true">4.1.</strong> od</a></li><li class="expanded "><a href="../binary/xxd.html"><strong aria-hidden="true">4.2.</strong> xxd</a></li><li class="expanded "><a href="../binary/readelf.html"><strong aria-hidden="true">4.3.</strong> readelf</a></li><li class="expanded "><a href="../binary/objdump.html"><strong aria-hidden="true">4.4.</strong> objdump</a></li><li class="expanded "><a href="../binary/nm.html"><strong aria-hidden="true">4.5.</strong> nm</a></li></ol></li><li class="expanded "><a href="../development/index.html"><strong aria-hidden="true">5.</strong> Development</a></li><li><ol class="section"><li class="expanded "><a href="../development/c++filt.html"><strong aria-hidden="true">5.1.</strong> c++filt</a></li><li class="expanded "><a href="../development/c++.html"><strong aria-hidden="true">5.2.</strong> c++</a></li><li class="expanded "><a href="../development/glibc.html"><strong aria-hidden="true">5.3.</strong> glibc</a></li><li class="expanded "><a href="../development/gcc.html"><strong aria-hidden="true">5.4.</strong> gcc</a></li><li class="expanded "><a href="../development/ld.so.html"><strong aria-hidden="true">5.5.</strong> ld.so</a></li></ol></li></ol> + </div> + <div id="sidebar-resize-handle" class="sidebar-resize-handle"></div> + </nav> + + <div id="page-wrapper" class="page-wrapper"> + + <div class="page"> + + <div id="menu-bar" class="menu-bar"> + <div id="menu-bar-sticky-container"> + <div class="left-buttons"> + <button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" 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(Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar"> + <i class="fa fa-search"></i> + </button> + + </div> + + <h1 class="menu-title">Notes</h1> + + <div class="right-buttons"> + <a href="../print.html" title="Print this book" aria-label="Print this book"> + <i id="print-button" class="fa fa-print"></i> + </a> + + </div> + </div> + </div> + + + <div id="search-wrapper" class="hidden"> + <form id="searchbar-outer" class="searchbar-outer"> + <input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header"> + </form> + <div id="searchresults-outer" class="searchresults-outer hidden"> + <div id="searchresults-header" class="searchresults-header"></div> + <ul id="searchresults"> + </ul> + </div> + </div> + + + <!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM --> + <script type="text/javascript"> + document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible'); + document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible'); + Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) { + link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1); + }); + </script> + + <div id="content" class="content"> + <main> + <h1><a class="header" href="#awk1" id="awk1">awk(1)</a></h1> +<pre><code class="language-markdown">awk [opt] program [input] + -F <sepstr> field separator string (can be regex) + program awk program + input file or stdin if not file given +</code></pre> +<h2><a class="header" href="#input-processing" id="input-processing">Input processing</a></h2> +<p>Input is processed in two stages:</p> +<ol> +<li>Splitting input into a sequence of <code>records</code>. +By default split at <code>newline</code> character, but can be changed via the +builtin <code>RS</code> variable.</li> +<li>Splitting a <code>record</code> into <code>fields</code>. By default strings without <code>whitespace</code>, +but can be changed via the builtin variable <code>FS</code> or command line option +<code>-F</code>.</li> +</ol> +<p>Fields are accessed as follows:</p> +<ul> +<li><code>$0</code> whole <code>record</code></li> +<li><code>$1</code> field one</li> +<li><code>$2</code> field two</li> +<li>...</li> +</ul> +<h2><a class="header" href="#program" id="program">Program</a></h2> +<p>An <code>awk</code> program is composed of pairs of the form:</p> +<pre><code class="language-markdown">pattern { action } +</code></pre> +<p>The program is run against each <code>record</code> in the input stream. If a <code>pattern</code> +matches a <code>record</code> the corresponding <code>action</code> is executed and can access the +<code>fields</code>.</p> +<pre><code class="language-markdown">INPUT + | + v +record ----> ∀ pattern matched + | | + v v +fields ----> run associated action +</code></pre> +<p>Any valid awk <code>expr</code> can be a <code>pattern</code>.</p> +<h3><a class="header" href="#special-pattern" id="special-pattern">Special pattern</a></h3> +<p>awk provides two special patterns, <code>BEGIN</code> and <code>END</code>, which can be used +multiple times. Actions with those patterns are <strong>executed exactly once</strong>.</p> +<ul> +<li><code>BEGIN</code> actions are run before processing the first record</li> +<li><code>END</code> actions are run after processing the last record</li> +</ul> +<h3><a class="header" href="#special-variables" id="special-variables">Special variables</a></h3> +<ul> +<li><code>RS</code> <em>record separator</em>: first char is the record separator, by default +<newline></li> +<li><code>FS</code> <em>field separator</em>: regex to split records into fields, by default +<space></li> +<li><code>NR</code> <em>number record</em>: number of current record</li> +</ul> +<h3><a class="header" href="#special-statements--functions" id="special-statements--functions">Special statements & functions</a></h3> +<ul> +<li> +<p><code>printf "fmt", args...</code></p> +<p>Print format string, args are comma separated.</p> +<ul> +<li><code>%s</code> string</li> +<li><code>%d</code> decimal</li> +<li><code>%x</code> hex</li> +<li><code>%f</code> float</li> +</ul> +<p>Width can be specified as <code>%Ns</code>, this reserves <code>N</code> chars for a string. +For floats one can use <code>%N.Mf</code>, <code>N</code> is the total number including <code>.</code> and +<code>M</code>.</p> +</li> +<li> +<p><code>strftime("fmt")</code></p> +<p>Print time stamp formatted by <code>fmt</code>.</p> +<ul> +<li><code>%Y</code> full year (eg 2020)</li> +<li><code>%m</code> month (01-12)</li> +<li><code>%d</code> day (01-31)</li> +<li><code>%F</code> alias for <code>%Y-%m-%d</code></li> +<li><code>%H</code> hour (00-23)</li> +<li><code>%M</code> minute (00-59)</li> +<li><code>%S</code> second (00-59)</li> +<li><code>%T</code> alias for <code>%H:%M:%S</code></li> +</ul> +</li> +</ul> +<h2><a class="header" href="#examples" id="examples">Examples</a></h2> +<h3><a class="header" href="#filter-records" id="filter-records">Filter records</a></h3> +<pre><code class="language-bash">awk 'NR%2 == 0 { print $0 }' <file> +</code></pre> +<p>The pattern <code>NR%2 == 0</code> matches every second record and the action <code>{ print $0 }</code> +prints the whole record.</p> +<h3><a class="header" href="#capture-in-variables" id="capture-in-variables">Capture in variables</a></h3> +<pre><code class="language-bash"># /proc/<pid>/status +# Name: cat +# ... +# VmRSS: 516 kB +# ... + +for f in /proc/*/status; do + cat $f | awk ' + /^VmRSS/ { rss = $2/1024 } + /^Name/ { name = $2 } + END { printf "%16s %6d MB\n", name, rss }'; +done | sort -k2 -n +</code></pre> +<p>We capture values from <code>VmRSS</code> and <code>Name</code> into variables and print them at the +<code>END</code> once processing all records is done.</p> +<h3><a class="header" href="#run-shell-command-and-capture-output" id="run-shell-command-and-capture-output">Run shell command and capture output</a></h3> +<pre><code class="language-bash">cat /proc/1/status | awk ' + /^Pid/ { + "ps --no-header -o user " $2 | getline user; + print user + }' +</code></pre> +<p>We build a <code>ps</code> command line and capture the first line of the processes output +in the <code>user</code> variable and then print it.</p> + + </main> + + <nav class="nav-wrapper" aria-label="Page navigation"> + <!-- Mobile navigation buttons --> + + <a rel="prev" href="../misc/git.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + + + <a rel="next" href="../misc/emacs.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + + + <div style="clear: both"></div> + </nav> + </div> + </div> + + <nav class="nav-wide-wrapper" aria-label="Page navigation"> + + <a href="../misc/git.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + + + <a href="../misc/emacs.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + + </nav> + + </div> + + + + + + + + + <script type="text/javascript"> + window.playpen_copyable = true; + </script> + + + + + + <script src="../elasticlunr.min.js" type="text/javascript" charset="utf-8"></script> + <script src="../mark.min.js" type="text/javascript" charset="utf-8"></script> + <script src="../searcher.js" type="text/javascript" charset="utf-8"></script> + + + <script src="../clipboard.min.js" type="text/javascript" charset="utf-8"></script> + <script src="../highlight.js" type="text/javascript" charset="utf-8"></script> + <script src="../book.js" type="text/javascript" charset="utf-8"></script> + + <!-- Custom JS scripts --> + + + + + </body> +</html> |