Re^2: system call (backticks) with pipes

What about a mixed case? I want variable substitution in part of the command.

 $boot_device = q awk 'FNR == 2 { print $1 }'; 
 $boot_device = `$boot_device`; 
 print "$boot_device\n";   

 $UUID_boot = q awk '{ print $2 }' | sed 's/"//g';
 $UUID_boot = `$UUID_boot`; 
 $print "$UUID_boot\n";
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I want $boot_device to be variable expanded but I don't want $2 to be expanded. Using q, the command is being sent as

blkid $boot_device | awk '{ print $2 }' | sed 's/"//g'
[download]

Using qq the command is being sent as

blkid /dev/md126p1 | awk '{ print }' | sed 's/"//g'
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which results in an error.

Comment on Re^2: system call (backticks) with pipes Select or Download Code

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Re^3: system call (backticks) with pipes by Corion (Patriarch) on Nov 17, 2016 at 20:26 UTC
Then you want to selectively quote the variables using backslashes or construct your strings more carefully by joining them together from other parts: `print "My two cents: \0.02\n"; my $cat = 'cat'; print "Some awk command: $cat \| awk '{ print \$2 }'\n";` [download] But maybe you just want to use Perl instead of `sed` and `awk`? There are even converters that give you the rough Perl code you need for an `awk` program. See a2p.	[reply] [d/l] [select]
Re^3: system call (backticks) with pipes by AnomalousMonk (Archbishop) on Nov 17, 2016 at 21:06 UTC
Judging by the unformatted, unreadable and as yet unreaped version of this post, `$boot_device = q awk 'FNR == 2 { print $1 }';` and similar are probably intended to be something like `$boot_device = q[ awk 'FNR == 2 { print $1 }'];` (and `$print` should be `print`). Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^3: system call (backticks) with pipes by hippo (Archbishop) on Nov 17, 2016 at 22:32 UTC
I want variable substitution in part of the command. So just escape those dollars which you want to pass as literals. `#!/usr/bin/env perl use strict; use warnings; use Test::More tests => 1; my $boot_device = '/dev/md126p1'; my $cmd = qq#blkid $boot_device \| awk '{ print \$2 }' \| sed 's/"//g'#; my $shouldbe = q#blkid /dev/md126p1 \| awk '{ print $2 }' \| sed 's/"//g +'#; is ($cmd, $shouldbe);` [download] And never pipe awk to sed - that would be pointless.	[reply] [d/l]