Perl - awk syntax error @array

Question

I need some assistance with getting awk to work in perl, or find a better alternative...

This code, returns an error about syntax at | when using the awk command to parse the detail.

my @LIST = `/bin/sh $DIR/ami-show.sh Version: | awk '{print $3}'`;

The exact error is

Use of uninitialized value $3 in concatenation (.) or string at test line 20, <STDIN> line 1.

Any help is greatly appreciated

EDIT: RESOLVED!!

Added \ to the '{print \$3}' all works as expected for this command.

Answer 1

As you have established already, the problem lies with the interpolation of the variable $3. Instead of escaping the $ to fix the problem, this can be circumvented completely by using perl to split the output of your command.

You should be able to do something like this in perl, using split rather than relying on awk. Note that the $3 used in your awk command corresponds to index number 2, due to arrays starting from index 0.

my $output = `/bin/sh $DIR/ami-show.sh Version:`;
my $column = (split ' ', $output)[2];

split takes a regular expression as its first argument (the pattern) and splits the string contained in the second argument. The code above splits the output of the command on any amount of white space, which is the same as what awk does by default.

edit: If you saw my first edit, I simply did split $output, omitting the pattern argument. This is actually valid, as not specifying a pattern invokes the same, awk-like behaviour.

Answer 2

You want to prevent Perl from interpolating the $3 variable. You could try to separate your awk command into its own string for better interpolation control:

my $awk = q(awk '{print $3}');
my @LIST = `/bin/sh $DIR/ami-show.sh Version: | $awk`;