running awk command in perl

Question

I have a tab delimited file(dummy) that looks like this :

a  b
a  b 
a  c
a  c
a  b

I am trying to write an awk command inside the perl script in which the file.txt is being made.

The awk command :

$n=system(" awk -F"\t" '{if($1=="a" && $2=="b") print $1,$2}' file.txt|wc -l ")

Error :
comparison operator :error in '==' , ',' between $1 and $2 in print }'

The awk script is running fine on command line but giving error while running inside the script.

I don't see any syntax error in the awk command.

Answer 1

Aside from the fact that what are you trying to achieve by executing awk from within perl (since it could be accomplished using the latter itself), you could use the q operator:

$cmd = q(awk -F"\t" '{if($1=="a" && $2=="b") print $1,$2}' file.txt | wc -l);
$n = system($cmd);

Note that using double-quotes would interpolate variables and you'd need to escape those.

Answer 2

You can get the number of a\tbs from Perl itself without calling an external command:

#!/usr/bin/perl
use warnings;
use strict;

open my $FH, '<', 'file.txt' or die $!;
my $n = 0;
"a\tb\n" eq $_ and $n++ while <$FH>;
print "$n\n";