mapping grep result to csv file - perl

Question

I'm trying to populate the grep result to csv file. But it is showing the following error.
"Use of uninitialized value in concatenation (.) or string at"
code:
sub gen_csv {
my $db_ptr = shift #_;
my $cvs_file_name = shift #_;
open( FILE, ">$cvs_file_name" ) or die("Unable to open CSV FILE $cvs_file_name\n");
print FILE "Channel no, Page no, \n";
foreach my $s ( #{$db_ptr} ) {
my $tmp = "$s->{'ch_no'},";
$tmp .= "$s->{'pg_no'},";
print FILE $tmp;
}
close(FILE);
}
sub parse_test_logs {
my $chnl;
my $page;
my $log = "sample.log";
open my $log_fh, "<", $log;
while ( my $line = <$log_fh> ) {
if ( $line =~ /(.*):.*solo_(.*): queueing.*/ ) {
my $chnl = $1;
my $page = $2;
}
my %test_details = (
'ch_no' => $chnl,
'pg_no' => $page, # <- was missing closing single quote
);
push( #{$dba_ptr}, \%test_details );
}
close log_fh;
}
Any suggestions on what i'm missing out?
(i'm getting the above error pointing to my $tmp = "$s->{'ch_no'},"; in gen_csv module)

Answer 1

Most likely this is due to NULL values in your DB records or the keys you are using are wrong. Either way, the warning is because the ch_no value does not exist.
If you don't care about NULL values, and you are fine with some of the values being missing, then you can suppress warnings for uninitialized values.
no warnings 'uninitialized';

Answer 2

Your problem involves this block:
if ( $line =~ /(.*):.*solo_(.*): queueing.*/ ) {
my $chnl = $1;
my $page = $2;
}
my %test_details = (
'ch_no' => $chnl,
'pg_no' => $page,
);
You're capturing your variables, but you have them declared with my within the if block. Those lexicals then go out of scope and are undef when used to initialize the hash.
I recommend simplifying your parsing function to the following:
sub parse_test_logs {
my $log = "sample.log";
open my $log_fh, "<", $log;
while (<$log_fh>) {
if ( my ( $chnl, $page ) = /(.*):.*solo_(.*): queueing.*/ ) {
push #{$dba_ptr}, { 'ch_no' => $chnl, 'pg_no' => $page };
} else {
warn "regex did not match for line $.: $_";
}
}
close $log_fh;
}
Finally, it's possible that you already are, but I just want to pass on the ever necessary advice to always include use strict; and use warnings; at the top of EVERY Perl script.