Re^2: Sort then conditionally sort

[lukez]

Hi Kyle, thank you sorry i didnt have code, I am JUST learning and I learn by looking at code solutions AND READING faqs and books etc.
I was confused about this part of your code;
my $op_io = <<'OP_INPUT_AND_OUTPUT';
and all the example before and after columns listed in between
OP_INPUT_AND_OUTPUT ;
My request for help had the columns on the left as an example of the input data file to be sorted... the 2 columns on the right are the sorted /cond sorted data that needs to go in a separate file. This confused me. thank you for taking the time to help me.

[kyle]

The construct is called a "here-document", and you can find them documented in perlop. It's basically a way to include some large chunk of text as a value in your program.

In this case, I used it to hold your example data. After setting $op_io to that value, I use split to cut it into individual lines, and I loop over those lines to pull the individual values out. When I'm done, I have your inputs and desired output.

I did it that way so I wouldn't have to reformat what you posted. I just pasted it in and wrote some code to pull out what I wanted.

[lukez]

Thanks Kyle, but How would this be adapted to read in a file and out put to another/

[kyle]

Have a look at open and print. This code does nothing but copy an input file to the output file to show their use. For your application, you'll want to do a lot more "stuff" between the reading and writing.

my $in_filename = 'in.txt';
my $out_filename = 'out.txt';

open my $in_fh, '<', $in_filename
    or die "Can't read '$in_filename': $!";
open my $out_fh, '>', $out_filename
    or die "Can't write '$out_filename': $!";

while ( my $in_line = <$in_fh> ) {
    print {$out_fh} $in_line;
}

close $in_fh    or die "close failed: $!";
close $out_fh   or die "Close failed: $!";