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    <p>Yes, it will interpolate the variable. However, I highly recommend two things:</p> <ul> <li>Use <code>qx/../</code> instead of back ticks.</li> <li>Set the command you're running first in a Perl variable, and then interpolate that variable.</li> </ul> <p>The <code>qx/../</code> is nice because it makes it more obvious what you're doing:</p> <pre><code>my $variable = qx(ls $directory); </code></pre> <p>You could use a wide variety of characters for <code>qx</code>:</p> <pre><code>my $variable = qx(ls $directory); my $variable = qx/ls $directory/; my $variable = qx^ls $directory^; my $variable = qx#ls $directory#; </code></pre> <p>The character after the <code>qx</code> will be used as <em>quotes</em>. If you use parentheses, square brackets, or curly braces, you use them in pairs with the opening one and closing one.</p> <p>This means that you can avoid issues where a particular character in your command might confuse things.</p> <p>The other thing is to build your command into a Perl variable and then execute it when you try to do interpolations. This gives you more control over what you're doing:</p> <pre><code>my $HOME; my $command; $HOME = "bin"; $command = "ls $HOME"; print qx($command); #Lists the directory bin $command = 'ls $HOME'; print qx($command); #List user's home directory </code></pre> <p>In both of these examples, I'm doing <code>qx($command)</code>. However, in the first example, I allow Perl to substitute the value of <code>$HOME. In the second example, I use single quotes, so Perl doesn't substitute the value of</code>$HOME<code>. Instead, the string</code>$HOME` is just part of my command I'm using. I'm letting the shell interpolates it.</p> <p>I usualy am leery of any program that uses <code>qx/.../</code>. In most cases, it's used to run a command that could be done in Perl itself. For example, in early Perl programs, you'd see things like this:</p> <pre><code> $date = `date +%M/%Y/%D` chop $date; #Yeah, I said EARLY Perl programs </code></pre> <p>Because it was simply a lot easier to run the Unix command rather than trying to do it in a pure Perl way. However, doing it the Perl (i.e. <em>the correct</em>) way means you're no longer dependent upon the OS's behavior which is not entirely under your control.</p> <p>If you need the output of the command for use in your Perl script, you should use <a href="http://perldoc.perl.org/functions/open.html" rel="noreferrer">open</a> to execute your command, and treat the output of the command as a file.</p> <pre><code>my $command = "ls $HOME"; open my command_fh, "|-", $command or die qq(Couldn't execute "$command"); </code></pre> <p>If you simply need to execute the command, use the <a href="http://perldoc.perl.org/functions/system.html" rel="noreferrer">system</a> command:</p> <pre><code>my $command = "xyz $date"; my $error = system $command; if ( $error ) { #Something terrible happened... } </code></pre> <p>Note that if you send only a single scalar argument to the <code>system</code> command, <strong><em>and</em></strong> it contains possible shell meta characters, it will execute the command via the OS shell. If you send the <code>system</code> command a list to execute, <strong><em>or</em></strong> there are no shell metacharacters, Perl will call the command executor to execute the command directly without any shell interpolations:</p> <pre><code>my @command = qw(ls $HOME); system @command; #Will print out "No such directory '$HOME' </code></pre>
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    1. POInterpolate perl variable in shell command
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    1. USDavid W.
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    1. CO@ David W. _ Thank you very much. This is an very much helpful information for newcomer like me.
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