Re^8: Filtering Output from two files

You have an error in this line:

while (my ($row) = <$fh2>) {
[download]

Since $row is in parenthesis, you're doing an assignment in list context. So all the lines in $fh2 are read, and the first one is passed into $row, and the rest are discarded.

Change the line to:

while (my $row = <$fh2>) {
[download]

and then it should work better for you.

Here's a little demonstration:

$ cat t.pl
use strict;
use warnings;

# Scalar context
my $row = <DATA>;
print $row;

# Array context
my ($a) = <DATA>;
print $a;

# Now there's nothing left!
my $c = <DATA>;
print $c;

__DATA__
Now is the time
for all good men
to come to the aid
of their party

$ perl t.pl
Now is the time
for all good men
Use of uninitialized value $c in print at t.pl line 14, <DATA> line 5.
[download]

Notice that we read the first line in scalar context, and then we print the first line successfully.

Next, we read a line in array context, and print the second line successfully.

Finally, we try to read the next line, but there's no data left! All of it was read earlier!

...roboticus

When your only tool is a hammer, all problems look like your thumb.

Comment on Re^8: Filtering Output from two files Select or Download Code

Replies are listed 'Best First'.
Re^9: Filtering Output from two files by Anonymous Monk on Feb 06, 2018 at 09:12 UTC
thank you i am able to do it now i wanna print the matching lines `print $row if exists $hash{$fields[0]};` something wrong with this syntax ?	[reply] [d/l]
Re^10: Filtering Output from two files by Anonymous Monk on Feb 06, 2018 at 09:22 UTC
i have excluded the part where i load the files to a hash i just wanna print the same values from both table	[reply]
Re^11: Filtering Output from two files by roboticus (Chancellor) on Feb 06, 2018 at 18:11 UTC
vighneshmufc: The syntax you showed on your previous message looks fine to just print the row that matches. In this message, though, you're saying you want to print the same values from both tables. To do that, you can use: `print $fields[0], " ", $row if exists $hash{$fields[0]};` [download] It's redundant, though, since the first column in $row (i.e. $fields[0]) is also the same value as you had in the first table. Suppose, however, your first file contained the key and some values, like the second file does. In that case, you need to change your first loop that loads up the hash. You'd split it on the delimiter just like you do for the second file, and then rather than just using `$hash{$line} = 1`, you'd store the value(s) you want, like: `my %hash=(); open (my $fh,'<',$file2) or die $!; while(my $line=<$fh>) { chomp $line; # Split the line into fields (first field is the key) my @fields = split /\\|/, $line; # store the entire line in the hash under the key $hash{$fields[0]} = $line; } close $fh; print "KEYS AND RECORDS ARE:\n"; print Dumper(\%hash);` [download] Once you have all your data in your hash, then you can print both rows when the keys match: `print $hash{$fields[0]}, " ", $row if exists $hash{$fields[0]};` [download] ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply] [d/l] [select]