zcat working in command line but not in perl script

Question

Here is a part of my script:

foreach $i ( @contact_list ) {

    print "$i\n";

    $e = "zcat $file_list2| grep $i";
    print "$e\n";

    $f = qx($e);
    print "$f";                                       
}

$e prints properly but $f gives a blank line even when $file_list2 has a match for $i.

Can anyone tell me why?

Answer 1

Always is better to use Perl's grep instead of using pipe :

@lines = `zcat $file_list2`;    # move output of zcat to array
die('zcat error') if ($?);      # will exit script with error if zcat is problem
# chomp(@lines)                 # this will remove "\n" from each line

foreach $i ( @contact_list ) {

    print "$i\n";

    @ar = grep (/$i/, @lines);
    print @ar;
#   print join("\n",@ar)."\n";      # in case of using chomp
}

Best solution is not calling zcat, but using zlib library : http://perldoc.perl.org/IO/Zlib.html

use IO::Zlib;

# ....
# place your defiiniton of $file_list2 and @contact list here.
# ...

$fh = new IO::Zlib; $fh->open($file_list2, "rb")
    or die("Cannot open $file_list2");
@lines = <$fh>;
$fh->close;

#chomp(@lines);                    #remove "\n" symbols from lines
foreach $i ( @contact_list ) {

    print "$i\n";
    @ar = grep (/$i/, @lines);
    print (@ar);
#   print join("\n",@ar)."\n";    #in case of using chomp
}