46 lines
1.2 KiB
HTML
46 lines
1.2 KiB
HTML
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
|
||
|
|
<html>
|
||
|
|
<head>
|
||
|
|
<meta name="generator" content="HTML Tidy, see www.w3.org">
|
||
|
|
<meta http-equiv="Content-Type" content=
|
||
|
|
"text/html; charset=utf-8">
|
||
|
|
<title>Conditional command</title>
|
||
|
|
<LINK rel="stylesheet" type="text/css" href="../rzahg/ic.css">
|
||
|
|
</HEAD>
|
||
|
|
<body bgcolor="#FFFFFF">
|
||
|
|
<!-- Java sync-link -->
|
||
|
|
<SCRIPT LANGUAGE="Javascript" SRC="../rzahg/synch.js" TYPE="text/javascript"></SCRIPT>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
<h2>Conditional command</h2>
|
||
|
|
|
||
|
|
<p>The syntax of the <strong>[[...]]</strong> command is</p>
|
||
|
|
|
||
|
|
<p><strong>[[</strong> <em>expression</em> <strong>]]</strong></p>
|
||
|
|
|
||
|
|
<p>It returns a status of 0 or 1 depending on the evaluation of the
|
||
|
|
conditional expression <em>expression</em>. The format of a conditional
|
||
|
|
expression is the same as the expressions evaluated by the
|
||
|
|
<a href="test.htm">test</a> utility.
|
||
|
|
<strong>qsh</strong> performs tilde expansion, parameter expansion, arithmetic
|
||
|
|
expansion, command substitution, and quote removal on <em>expression</em>
|
||
|
|
before it is evaluated.
|
||
|
|
</p>
|
||
|
|
|
||
|
|
<p><strong>Examples</strong></p>
|
||
|
|
|
||
|
|
<ol>
|
||
|
|
<li>A conditional command that uses a command substitution.
|
||
|
|
<pre>
|
||
|
|
if [[ $(grep -c apple fruits.txt) -eq 0 ]]
|
||
|
|
then
|
||
|
|
echo There are no apples in fruit.txt
|
||
|
|
fi
|
||
|
|
</pre>
|
||
|
|
</li>
|
||
|
|
</ol>
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|