validate 32bit integer with regex - perl

Question

I'm trying to come up with a regex that will match anything that is not a 32bit integer. My eventual goal is to match lines that are not in the following format
Integer\tInteger\tInteger\tInteger\tInteger\tInteger\tInteger
(7 32bit integers and 1 tab in between each integer)
So far I've come up with this
#!/usr/bin/perl -w
use strict;
while ( my $line = <> ) {
if ( $line =~ /^(429496729[0-6]|42949672[0-8]\d|4294967[01]\d{2}|429496[0-6]\d{3}|42949[0-5]\d{4}|4294[0-8]\d{5}|429[0-3]\d{6}|42[0-8]\d{7}|4[01]\d{8}|[1-3]\d{9}|[1-9]\d{8}|[1-9]\d{7}|[1-9]\d{6}|[1-9]\d{5}|[1-9]\d{4}|[1-9]\d{3}|[1-9]\d{2}|[1-9]\d|\d)$/ ) {
print "Match at line $.\n";
print "$line"
}
}
But I can't even get to the first step of having the regex match a 32bit numbers (once I tackle that problem I can tackle having the tabs be the way they need to be)
Am I solving this problem the right way? Any thoughts?

Answer 1

Am I solving this problem the right way?
Assuming validation is actually needed, my first approach would be to split on tabs, check the number of fields, check each field but not by using a regex. Doing a range check in a regex is silly! (Padding using sprintf then doing a string compare would solve overflow problems.)
Other issues:
\d matches far more than just 0-9. Use /\d/a or /[0-9]/ if you want to match just 0-9.
What about negative numbers? 32-bit integers can also be used to store 2147483647..-2147483648.
What about leading zeros and leading plus or minus signs?
What about thousand separators?
Is 10.0 an integer? Mathematically speaking, it is. Perl would also store that as an integer.

Answer 2

I would say no, this is not the correct way - it's very hard to try and follow that regex; while it can be done, consider if it'll make sense tomorrow. Or how hard it will be to alter if the range changes or a slight variation to the format is required :)
Here are my suggestions:
Read Is it a Number? to find out how to tell if a value is a number and, if so, extract it as one. That is, get a real numeric value, not a string. Additional checks can be done at this stage if desired to restrict what "valid" numbers are; don't restrict the range, just the format.
Use a simple range check for the extracted number - between 0 and 232-1 in this case?

Answer 3

You could do it all in a regex, but it's better to treat them as numbers and use math.
# Split it into fields.
my #fields = split /\t/, $line;
# Scan for fields which do not look like integers
# or are outside the unsigned 32 bit integer range
my $valid_line = !grep { /[^0-9]/ || ($_ < 0) || (2**32-1 < $_) } #fields;
All the caveats in the other answers about "what is a 32 bit integer" still apply. Is "+10" valid? "10.0"? Can't answer that without knowing why you're filtering for these numbers, adjust the logic as necessary.
And just to throw in a perl5i plug...
use perl5i::2;
my $valid_line = !grep { $_->is_integer && ($_ < 0) || (2**32-1 < $_) } #fields;