hyperreal/wiki.bash-hackers.org
1
0
Fork 0
mirror of https://github.com/rawiriblundell/wiki.bash-hackers.org synced 2024-11-02 00:53:07 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity
203e0f4ea8
wiki.bash-hackers.org/syntax/expansion/arith
Rawiri Blundell 80bd32e686 First crawl of archive.org
2023-04-14 23:44:41 +12:00

394 lines
27 KiB
Plaintext
Raw Blame History

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" dir="ltr" class="no-js">
<head><script type="text/javascript" src="/_static/js/bundle-playback.js?v=TPXmWR5s" charset="utf-8"></script>
<script type="text/javascript" src="/_static/js/wombat.js?v=txqj7nKC" charset="utf-8"></script>
<script type="text/javascript">
__wm.init("http://web.archive.org/web");
__wm.wombat("https://wiki.bash-hackers.org/syntax/expansion/arith?do=edit","20220706154025","http://web.archive.org/","web","/_static/",
"1657122025");
</script>
<link rel="stylesheet" type="text/css" href="/_static/css/banner-styles.css?v=S1zqJCYt" />
<link rel="stylesheet" type="text/css" href="/_static/css/iconochive.css?v=qtvMKcIJ" />
<!-- End Wayback Rewrite JS Include -->
<meta charset="UTF-8"/>
<title>Arithmetic expansion [Bash Hackers Wiki]</title>
<script>(function(H){H.className=H.className.replace(/\bno-js\b/,'js')})(document.documentElement)</script>
<meta name="viewport" content="width=device-width,initial-scale=1"/>
<link rel="shortcut icon" href="/web/20220706154025im_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/images/favicon.ico"/>
<link rel="apple-touch-icon" href="/web/20220706154025im_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/images/apple-touch-icon.png"/>
<meta name="generator" content="DokuWiki"/>
<meta name="robots" content="noindex,nofollow"/>
<link type="text/css" rel="stylesheet" href="/web/20220706154025cs_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/assets/bootstrap/default/bootstrap.min.css"/>
<link rel="search" type="application/opensearchdescription+xml" href="/web/20220706154025/https://wiki.bash-hackers.org/lib/exe/opensearch.php" title="Bash Hackers Wiki"/>
<link rel="start" href="/"/>
<link rel="contents" href="/syntax/expansion/arith?do=index" title="Sitemap"/>
<link rel="manifest" href="/web/20220706154025/https://wiki.bash-hackers.org/lib/exe/manifest.php"/>
<link rel="alternate" type="application/rss+xml" title="Recent Changes" href="/web/20220706154025/https://wiki.bash-hackers.org/feed.php"/>
<link rel="alternate" type="application/rss+xml" title="Current namespace" href="/web/20220706154025/https://wiki.bash-hackers.org/feed.php?mode=list&amp;ns=syntax:expansion"/>
<link rel="alternate" type="text/html" title="Plain HTML" href="/web/20220706154025/https://wiki.bash-hackers.org/_export/xhtml/syntax/expansion/arith"/>
<link rel="alternate" type="text/plain" title="Wiki Markup" href="/web/20220706154025/https://wiki.bash-hackers.org/_export/raw/syntax/expansion/arith"/>
<link rel="stylesheet" type="text/css" href="/web/20220706154025cs_/https://wiki.bash-hackers.org/lib/exe/css.php?t=bootstrap3&amp;tseed=54923c3deda180f2db5bd755cd8fbf1a"/>
<!--[if gte IE 9]><!-->
<script type="text/javascript">/*<![CDATA[*/var NS='syntax:expansion';var JSINFO = {"updatable":1,"userreplace":1,"default_macro_string":"","plugins":{"edittable":{"default columnwidth":""}},"move_renameokay":false,"isadmin":0,"isauth":0,"bootstrap3":{"mode":"source","toc":[],"config":{"collapsibleSections":0,"fixedTopNavbar":1,"showSemanticPopup":0,"sidebarOnNavbar":0,"tagsOnTop":1,"tocAffix":1,"tocCollapseOnScroll":1,"tocCollapsed":0,"tocLayout":"default","useAnchorJS":1,"useAlternativeToolbarIcons":1}},"id":"syntax:expansion:arith","namespace":"syntax:expansion","ACT":"source","useHeadingNavigation":1,"useHeadingContent":1};
/*!]]>*/</script>
<script type="text/javascript" charset="utf-8" src="/web/20220706154025js_/https://wiki.bash-hackers.org/lib/exe/jquery.php?tseed=23f888679b4f1dc26eef34902aca964f"></script>
<script type="text/javascript" charset="utf-8" src="/web/20220706154025js_/https://wiki.bash-hackers.org/lib/exe/js.php?t=bootstrap3&amp;tseed=54923c3deda180f2db5bd755cd8fbf1a"></script>
<script type="text/javascript">/*<![CDATA[*/if (typeof IconifyConfig == 'undefined') { var IconifyConfig = { 'defaultAPI' : '/lib/tpl/bootstrap3/iconify.php?prefix={prefix}&icons={icons}' } }
/*!]]>*/</script>
<script type="text/javascript" src="/web/20220706154025js_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/assets/bootstrap/js/bootstrap.min.js"></script>
<script type="text/javascript" src="/web/20220706154025js_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/assets/anchorjs/anchor.min.js"></script>
<script type="text/javascript" src="/web/20220706154025js_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/assets/typeahead/bootstrap3-typeahead.min.js"></script>
<script type="text/javascript" src="/web/20220706154025js_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/assets/iconify/iconify.min.js"></script>
<script type="text/javascript" src="/web/20220706154025js_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/assets/iconify/plugins/fa.js"></script>
<!--<![endif]-->
<style type="text/css">@media screen { body { margin-top: 65px; } #dw__toc.affix { top: 55px; position: fixed !important; } #dw__toc .nav .nav .nav { display: none; } }</style>
<!--[if lt IE 9]>
<script type="text/javascript" src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
<script type="text/javascript" src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
<![endif]-->
</head>
<body class="default dokuwiki mode_source tpl_bootstrap3 dw-page-on-panel dw-fluid-container" data-page-id="syntax:expansion:arith"><div class="dokuwiki">
<header id="dokuwiki__header" class="dw-container dokuwiki container-fluid mx-5">
<!-- navbar -->
<nav id="dw__navbar" class="navbar navbar-fixed-top navbar-default" role="navigation">
<div class="dw-container container-fluid mx-5">
<div class="navbar-header">
<button class="navbar-toggle" type="button" data-toggle="collapse" data-target=".navbar-collapse">
<span class="icon-bar"></span>
<span class="icon-bar"></span>
<span class="icon-bar"></span>
</button>
<a class="navbar-brand d-flex align-items-center" href="/web/20220706154025/https://wiki.bash-hackers.org/start" accesskey="h" title="Bash Hackers Wiki"><img id="dw__logo" class="pull-left h-100 mr-4" alt="Bash Hackers Wiki" src="/web/20220706154025im_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/images/logo.png"/><div class="pull-right"><div id="dw__title">Bash Hackers Wiki</div></div></a>
</div>
<div class="collapse navbar-collapse">
<div class="navbar-right" id="dw__navbar_items">
<!-- navbar-searchform -->
<form action="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith" accept-charset="utf-8" class="navbar-form navbar-left search" id="dw__search" method="get" role="search">
<div class="input-group">
<input id="qsearch" autocomplete="off" type="search" placeholder="Search" value="" accesskey="f" name="q" class="form-control" title="[F]"/>
<div class="input-group-btn">
<button class="btn btn-default" type="submit" title="Search">
<span class="iconify" data-icon="mdi:magnify"></span> </button>
</div>
</div>
<input type="hidden" name="do" value="search"/>
</form>
<!-- /navbar-searchform -->
<!-- tools-menu -->
<ul class="nav navbar-nav dw-action-icon" id="dw__tools">
<li class="dropdown">
<a href="" class="dropdown-toggle" data-target="#" data-toggle="dropdown" title="" role="button" aria-haspopup="true" aria-expanded="false">
<span class="iconify" data-icon="mdi:wrench"></span> <span class="hidden-lg hidden-md hidden-sm">Tools</span> <span class="caret"></span>
</a>
<ul class="dropdown-menu tools" role="menu">
<li class="dropdown-header">
<span class="iconify" data-icon="mdi:account"></span> User Tools </li>
<li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=register" title="Register" rel="nofollow" class="menuitem register"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M15 14c-2.67 0-8 1.33-8 4v2h16v-2c0-2.67-5.33-4-8-4m-9-4V7H4v3H1v2h3v3h2v-3h3v-2m6 2a4 4 0 0 0 4-4 4 4 0 0 0-4-4 4 4 0 0 0-4 4 4 4 0 0 0 4 4z"/></svg><span>Register</span></a></li><li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=login&amp;sectok=" title="Log In" rel="nofollow" class="menuitem login"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M10 17.25V14H3v-4h7V6.75L15.25 12 10 17.25M8 2h9a2 2 0 0 1 2 2v16a2 2 0 0 1-2 2H8a2 2 0 0 1-2-2v-4h2v4h9V4H8v4H6V4a2 2 0 0 1 2-2z"/></svg><span>Log In</span></a></li>
<li class="divider" role="separator"></li>
<li class="dropdown-header">
<span class="iconify" data-icon="mdi:toolbox"></span> Site Tools </li>
<li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=recent" title="Recent Changes [r]" rel="nofollow" accesskey="r" class="menuitem recent"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M15 13h1.5v2.82l2.44 1.41-.75 1.3L15 16.69V13m4-5H5v11h4.67c-.43-.91-.67-1.93-.67-3a7 7 0 0 1 7-7c1.07 0 2.09.24 3 .67V8M5 21a2 2 0 0 1-2-2V5c0-1.11.89-2 2-2h1V1h2v2h8V1h2v2h1a2 2 0 0 1 2 2v6.1c1.24 1.26 2 2.99 2 4.9a7 7 0 0 1-7 7c-1.91 0-3.64-.76-4.9-2H5m11-9.85A4.85 4.85 0 0 0 11.15 16c0 2.68 2.17 4.85 4.85 4.85A4.85 4.85 0 0 0 20.85 16c0-2.68-2.17-4.85-4.85-4.85z"/></svg><span>Recent Changes</span></a></li><li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=media&amp;ns=syntax%3Aexpansion" title="Media Manager" rel="nofollow" class="menuitem media"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M7 15l4.5-6 3.5 4.5 2.5-3L21 15m1-11h-8l-2-2H6a2 2 0 0 0-2 2v12a2 2 0 0 0 2 2h16a2 2 0 0 0 2-2V6a2 2 0 0 0-2-2M2 6H0v14a2 2 0 0 0 2 2h18v-2H2V6z"/></svg><span>Media Manager</span></a></li><li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=index" title="Sitemap [x]" rel="nofollow" accesskey="x" class="menuitem index"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M3 3h6v4H3V3m12 7h6v4h-6v-4m0 7h6v4h-6v-4m-2-4H7v5h6v2H5V9h2v2h6v2z"/></svg><span>Sitemap</span></a></li>
<li class="divider" role="separator"></li>
<li class="dropdown-header">
<span class="iconify" data-icon="mdi:file-document-outline"></span> Page Tools </li>
<li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=" title="Show page [v]" rel="nofollow" accesskey="v" class="menuitem show"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M13 9h5.5L13 3.5V9M6 2h8l6 6v12a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2V4c0-1.11.89-2 2-2m9 16v-2H6v2h9m3-4v-2H6v2h12z"/></svg><span>Show page</span></a></li><li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=revisions" title="Old revisions [o]" rel="nofollow" accesskey="o" class="menuitem revs"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M11 7v5.11l4.71 2.79.79-1.28-4-2.37V7m0-5C8.97 2 5.91 3.92 4.27 6.77L2 4.5V11h6.5L5.75 8.25C6.96 5.73 9.5 4 12.5 4a7.5 7.5 0 0 1 7.5 7.5 7.5 7.5 0 0 1-7.5 7.5c-3.27 0-6.03-2.09-7.06-5h-2.1c1.1 4.03 4.77 7 9.16 7 5.24 0 9.5-4.25 9.5-9.5A9.5 9.5 0 0 0 12.5 2z"/></svg><span>Old revisions</span></a></li><li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=backlink" title="Backlinks" rel="nofollow" class="menuitem backlink"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M10.59 13.41c.41.39.41 1.03 0 1.42-.39.39-1.03.39-1.42 0a5.003 5.003 0 0 1 0-7.07l3.54-3.54a5.003 5.003 0 0 1 7.07 0 5.003 5.003 0 0 1 0 7.07l-1.49 1.49c.01-.82-.12-1.64-.4-2.42l.47-.48a2.982 2.982 0 0 0 0-4.24 2.982 2.982 0 0 0-4.24 0l-3.53 3.53a2.982 2.982 0 0 0 0 4.24m2.82-4.24c.39-.39 1.03-.39 1.42 0a5.003 5.003 0 0 1 0 7.07l-3.54 3.54a5.003 5.003 0 0 1-7.07 0 5.003 5.003 0 0 1 0-7.07l1.49-1.49c-.01.82.12 1.64.4 2.43l-.47.47a2.982 2.982 0 0 0 0 4.24 2.982 2.982 0 0 0 4.24 0l3.53-3.53a2.982 2.982 0 0 0 0-4.24.973.973 0 0 1 0-1.42z"/></svg><span>Backlinks</span></a></li><li class="action"><a href="#dokuwiki__top" title="Back to top [t]" rel="nofollow" accesskey="t" class="menuitem top"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8v12z"/></svg><span>Back to top</span></a></li>
</ul>
</li>
</ul>
<!-- /tools-menu -->
<ul class="nav navbar-nav">
<li>
<span class="dw__actions dw-action-icon">
<a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=register" title="Register" rel="nofollow" class="menuitem register btn btn-success navbar-btn"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M15 14c-2.67 0-8 1.33-8 4v2h16v-2c0-2.67-5.33-4-8-4m-9-4V7H4v3H1v2h3v3h2v-3h3v-2m6 2a4 4 0 0 0 4-4 4 4 0 0 0-4-4 4 4 0 0 0-4 4 4 4 0 0 0 4 4z"/></svg><span class=""> Register</span></a><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=login&amp;sectok=" title="Log In" rel="nofollow" class="menuitem login btn btn-default navbar-btn"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M10 17.25V14H3v-4h7V6.75L15.25 12 10 17.25M8 2h9a2 2 0 0 1 2 2v16a2 2 0 0 1-2 2H8a2 2 0 0 1-2-2v-4h2v4h9V4H8v4H6V4a2 2 0 0 1 2-2z"/></svg><span class=""> Log In</span></a> </span>
</li>
</ul>
</div>
</div>
</div>
</nav>
<!-- navbar -->
<div align="center">
<script async src="//web.archive.org/web/20220706154025js_/https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<!-- BHORG_BOTTOM -->
<ins class="adsbygoogle" style="display:inline-block;width:728px;height:90px" data-ad-client="ca-pub-4658830517838678" data-ad-slot="1603598940"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>
</div>
</header>
<a name="dokuwiki__top" id="dokuwiki__top"></a>
<main role="main" class="dw-container pb-5 dokuwiki container-fluid mx-5">
<div id="dokuwiki__pageheader">
<!-- breadcrumbs -->
<nav id="dw__breadcrumbs" class="small">
<hr/>
<div class="dw__youarehere">
<ol class="breadcrumb" itemscope itemtype="http://schema.org/BreadcrumbList"><li>You are here</li><li itemprop="itemListElement" itemscope itemtype="http://schema.org/ListItem"><a href="/web/20220706154025/https://wiki.bash-hackers.org/start" itemprop="item" title="start"><span itemprop="name"><span class="iconify" data-icon="mdi:home"></span></span></a></li><li itemprop="itemListElement" itemscope itemtype="http://schema.org/ListItem"><a itemprop="item" href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/start" class="wikilink1" title="syntax:start">Syntax</a></li><li itemprop="itemListElement" itemscope itemtype="http://schema.org/ListItem"><a itemprop="item" href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/start" class="wikilink1" title="syntax:expansion:start">Syntax: Expansions</a></li><li class="active" itemprop="itemListElement" itemscope itemtype="http://schema.org/ListItem"><span itemprop="name"><a itemprop="item" href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith" class="wikilink1" title="syntax:expansion:arith">Arithmetic expansion</a></span></li></ol> </div>
<div class="dw__breadcrumbs hidden-print">
<ol class="breadcrumb"><li>Trace</li> </div>
<hr/>
</nav>
<!-- /breadcrumbs -->
<p class="text-right">
<span class="pageId ml-1 label label-primary">syntax:expansion:arith</span> </p>
<div id="dw__msgarea" class="small">
</div>
</div>
<div class="row">
<article id="dokuwiki__content" class="col-sm-12 col-md-12 " itemscope itemtype="http://schema.org/Article" itemref="dw__license">
<!-- page-tools -->
<nav id="dw__pagetools" class="hidden-print">
<div class="tools panel panel-default">
<ul class="nav nav-stacked nav-pills text-muted">
<li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=" title="Show page [v]" rel="nofollow" accesskey="v" class="menuitem show"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M13 9h5.5L13 3.5V9M6 2h8l6 6v12a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2V4c0-1.11.89-2 2-2m9 16v-2H6v2h9m3-4v-2H6v2h12z"/></svg><span>Show page</span></a></li><li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=revisions" title="Old revisions [o]" rel="nofollow" accesskey="o" class="menuitem revs"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M11 7v5.11l4.71 2.79.79-1.28-4-2.37V7m0-5C8.97 2 5.91 3.92 4.27 6.77L2 4.5V11h6.5L5.75 8.25C6.96 5.73 9.5 4 12.5 4a7.5 7.5 0 0 1 7.5 7.5 7.5 7.5 0 0 1-7.5 7.5c-3.27 0-6.03-2.09-7.06-5h-2.1c1.1 4.03 4.77 7 9.16 7 5.24 0 9.5-4.25 9.5-9.5A9.5 9.5 0 0 0 12.5 2z"/></svg><span>Old revisions</span></a></li><li class="action"><a href="/web/20220706154025/https://wiki.bash-hackers.org/syntax/expansion/arith?do=backlink" title="Backlinks" rel="nofollow" class="menuitem backlink"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M10.59 13.41c.41.39.41 1.03 0 1.42-.39.39-1.03.39-1.42 0a5.003 5.003 0 0 1 0-7.07l3.54-3.54a5.003 5.003 0 0 1 7.07 0 5.003 5.003 0 0 1 0 7.07l-1.49 1.49c.01-.82-.12-1.64-.4-2.42l.47-.48a2.982 2.982 0 0 0 0-4.24 2.982 2.982 0 0 0-4.24 0l-3.53 3.53a2.982 2.982 0 0 0 0 4.24m2.82-4.24c.39-.39 1.03-.39 1.42 0a5.003 5.003 0 0 1 0 7.07l-3.54 3.54a5.003 5.003 0 0 1-7.07 0 5.003 5.003 0 0 1 0-7.07l1.49-1.49c-.01.82.12 1.64.4 2.43l-.47.47a2.982 2.982 0 0 0 0 4.24 2.982 2.982 0 0 0 4.24 0l3.53-3.53a2.982 2.982 0 0 0 0-4.24.973.973 0 0 1 0-1.42z"/></svg><span>Backlinks</span></a></li><li class="action"><a href="#dokuwiki__top" title="Back to top [t]" rel="nofollow" accesskey="t" class="menuitem top"><svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewbox="0 0 24 24"><path d="M13 20h-2V8l-5.5 5.5-1.42-1.42L12 4.16l7.92 7.92-1.42 1.42L13 8v12z"/></svg><span>Back to top</span></a></li> </ul>
</div>
</nav>
<!-- /page-tools -->
<div class="panel panel-default px-3 py-2" itemprop="articleBody">
<div class="page panel-body">
<div class="dw-content-page "><!-- content --><div class="dw-content"><p>
This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
</p>
<div class="editBox" role="application">
<div class="toolbar group">
<div id="draft__status" class="draft__status"></div>
<div id="tool__bar" class="tool__bar"></div>
</div>
<form id="dw__editform" method="post" action="" accept-charset="utf-8" class=" form-inline"><div class="no">
<input type="hidden" name="sectok" value=""/><input type="hidden" name="id" value="syntax:expansion:arith"/><input type="hidden" name="rev" value="0"/><input type="hidden" name="date" value="0"/><input type="hidden" name="prefix" value="."/><input type="hidden" name="suffix" value=""/><input type="hidden" name="changecheck" value="b0c6013f7451ddbc54cdbe31f7b040ac"/><input type="hidden" name="target" value="section"/><textarea name="wikitext" id="wiki__text" dir="auto" class="edit form-control" cols="80" rows="10" tabindex="1" readonly="readonly">
====== Arithmetic expansion ======
&lt;code&gt;
$(( &lt;EXPRESSION&gt; ))
$[ &lt;EXPRESSION&gt; ]
&lt;/code&gt;
The [[syntax:arith_expr | arithmetic expression]] ''&lt;EXPRESSION&gt;'' is evaluated and expands to the result. The output of the arithmetic expansion is guaranteed to be one word and a digit in Bash.
Please **do not use the second form ''$[ ... ]''**! It's deprecated. The preferred and standardized form is ''&lt;nowiki&gt;$(( ... ))&lt;/nowiki&gt;''!
Example
&lt;code bash&gt;
function printSum {
typeset -A args
typeset name
for name in first second; do
[[ -t 0 ]] &amp;&amp; printf 'Enter %s positive integer: ' &quot;$name&quot; &gt;&amp;2
read -r ${BASH_VERSION+-e} &quot;args[$name]&quot;
[[ ${args[$name]} == +([[:digit:]]) ]] || return 1 # Validation is extremely important whenever user input is used in arithmetic.
done
printf 'The sum is %d.' $((${args[first]} + ${args[second]}))
}
&lt;/code&gt;
**Note** that in Bash you don't need the arithmetic expansion to check for the boolean value of an arithmetic expression. This can be done using the [[syntax:ccmd:arithmetic_eval | arithmetic evaluation compound command]]:
&lt;code bash&gt;
printf %s 'Enter a number: ' &gt;&amp;2
read -r number
if ((number == 1234)); then
echo 'Good guess'
else
echo 'Haha... :-P'
fi
&lt;/code&gt;
**Variables** used inside the arithmetic expansion, as in all arithmetic contexts, can be used with or without variable expansion:
&lt;code bash&gt;
x=1
echo $((x)) # Good.
echo $(($x)) # Ok. Avoid expansions within arithmetic. Use variables directly.
echo $((&quot;$x&quot;)) # Error. There is no quote-removal in arithmetic contexts. It expands to $((&quot;1&quot;)), which is an invalid arithmetic expression.
echo $((x[0])) # Good.
echo $((${x[0]})) # Ok. Nested expansion again.
echo $((${x[$((${x[!$x]}-$x))]})) # Same as above but more ridiculous.
echo $(($x[0])) # Error. This expands to $((1[0])), an invalid expression.
&lt;/code&gt;
===== Bugs and Portability considerations =====
* The original Bourne shell doesn't have arithmetic expansions. You have to use something like ''expr(1)'' within backticks instead. Since ''expr'' is horrible (as are backticks), and arithmetic expansion is required by POSIX, you should not worry about this, and preferably fix any code you find that's still using ''expr''.
===== See also =====
* [[syntax:arith_expr | arithmetic expressions]]
* [[syntax:ccmd:arithmetic_eval | arithmetic evaluation compound command]]
* [[syntax:expansion:intro | Introduction to expansion and substitution]]
* [[http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_04 | POSIX definition]]
</textarea>
<div id="wiki__editbar" class="editBar">
<div id="size__ctl">
</div>
</div>
</div></form>
</div>
</div><!-- /content --></div>
</div>
</div>
<div class="small text-right">
<span class="docInfo">
<ul class="list-inline"><li><span class="iconify text-muted" data-icon="mdi:file-document-outline"></span> <span title="syntax/expansion/arith.txt">syntax/expansion/arith.txt</span></li><li><span class="iconify text-muted" data-icon="mdi:calendar"></span> Last modified: <span title="2013/01/08 14:49">2013/01/08 14:49</span></li><li class="text-muted">by <bdi>ormaaj</bdi></li></ul> </span>
</div>
</article>
</div>
</main>
<footer id="dw__footer" class="dw-container py-5 dokuwiki container-fluid">
<hr/>
<div align="center">
<h3><a target="_blank" href="http://web.archive.org/web/20220706154025/http://www.performing-databases.com/">This site is supported by Performing Databases - your experts for database administration</a></h3>
</div>
<hr/>
<div align="center">
<script async src="//web.archive.org/web/20220706154025js_/https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<!-- BHORG_BOTTOM -->
<ins class="adsbygoogle" style="display:inline-block;width:728px;height:90px" data-ad-client="ca-pub-4658830517838678" data-ad-slot="1603598940"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>
</div>
<!-- footer -->
<div class="dw-container small container-fluid mx-5">
<div class="footer-dw-title">
<div class="media">
<div class="media-left">
<img src="/web/20220706154025im_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/images/logo.png" alt="Bash Hackers Wiki" class="media-object" style="height:32px"/>
</div>
<div class="media-body">
<div class="row">
<div class="col-sm-2">
<h4 class="media-heading">Bash Hackers Wiki</h4>
<p>
</p>
</div>
<div class="col-sm-10">
</div>
</div>
</div>
</div>
</div>
<div class="footer-license row">
<hr/>
<div id="dw__license" class="col-sm-6">
<p>
<a href="http://web.archive.org/web/20220706154025/http://www.gnu.org/licenses/fdl-1.3.html" title="GNU Free Documentation License 1.3" target="" itemscope itemtype="http://schema.org/CreativeWork" itemprop="license" rel="license" class="license"><img src="/web/20220706154025im_/https://wiki.bash-hackers.org/lib/tpl/bootstrap3/images/license/gnufdl.png" width="24" height="24" alt="gnufdl"/> </a> </p>
<p class="small">
Except where otherwise noted, content on this wiki is licensed under the following license:<br/><a href="http://web.archive.org/web/20220706154025/http://www.gnu.org/licenses/fdl-1.3.html" title="GNU Free Documentation License 1.3" target="" itemscope itemtype="http://schema.org/CreativeWork" itemprop="license" rel="license" class="license">GNU Free Documentation License 1.3</a> </p>
</div>
<div class="col-sm-6">
</div>
</div>
</div>
<!-- /footer -->
</footer>
<a href="#dokuwiki__top" class="back-to-top hidden-print btn btn-default" title="skip to content" accesskey="t">
<span class="iconify" data-icon="mdi:chevron-up"></span> </a>
<div id="screen__mode"> <span class="visible-xs-block"></span>
<span class="visible-sm-block"></span>
<span class="visible-md-block"></span>
<span class="visible-lg-block"></span>
</div>
<img src="/web/20220706154025im_/https://wiki.bash-hackers.org/lib/exe/indexer.php?id=syntax%3Aexpansion%3Aarith&amp;1657122027" width="2" height="1" alt=""/>
</div>
</body>
</html>
<!--
FILE ARCHIVED ON 15:40:25 Jul 06, 2022 AND RETRIEVED FROM THE
INTERNET ARCHIVE ON 11:36:46 Apr 14, 2023.
JAVASCRIPT APPENDED BY WAYBACK MACHINE, COPYRIGHT INTERNET ARCHIVE.
ALL OTHER CONTENT MAY ALSO BE PROTECTED BY COPYRIGHT (17 U.S.C.
SECTION 108(a)(3)).
-->
<!--
playback timings (ms):
captures_list: 334.224
exclusion.robots: 0.165
exclusion.robots.policy: 0.152
cdx.remote: 0.095
esindex: 0.014
LoadShardBlock: 294.234 (3)
PetaboxLoader3.resolve: 449.551 (2)
PetaboxLoader3.datanode: 47.843 (4)
load_resource: 244.916
-->
Reference in New Issue View Git Blame Copy Permalink