Reading chunks of data in Perl

Question

What good is it in Perl to split a string into chunks of different lengths when there is no separator that I can use. My data is ordered by column length, so the first variable is at positions 1-4, the second variable is at positions 5-15, etc. There are many variables, each of which has a different length.

In other words, is there a way to use the split function, based on the position in the line, and not on matching the expression?

Thanks.

Answer 1

Yes there is. The unpack function is well suited for working with fixed-width records.

Example

 my $record = "1234ABCDEFGHIJK"; my @fields = unpack 'A4A11', $record; # 1st field is 4 chars long, 2nd is 11 print "@fields"; # Prints '1234 ABCDEFGHIJK' 

The first argument is a template that tells unpack where the fields begin and end. The second argument indicates which line to unpack.

unpack can also be said to ignore character positions in a string by specifying zero bytes, x . The 'A4x2A9' can be used to ignore "AB" in the above example.

See perldoc -f pack and perldoc perlpacktut for details and examples.

Answer 2

Instead of using split try the method

Answer 3

You can use the substr() function to retrieve data by offset:

 $first = substr($line, 0, 4); $second = substr($line, 4, 11); 

Another option is to use a regex:

 ($first, $second) = ($line =~ /(.{4})(.{11})/);