Perl regex from file.txt, match columns greater than x - regex

Question

I have a file containing several rows of code, like this:
160101, 0100, 58.8,
160101, 0200, 59.3,
160101, 0300, 59.5,
160101, 0400, 59.1,
I'm trying to print out the third column with a regex, like this:
# Read the text file.
open( IN, "file.txt" ) or die "Can't read words file: $!";
# Print out.
while (<IN>) {
print "Number: $1\n"
while s/[^\,]+\,[^\,]+\,([^\,]+)\,/$1/g;
}
And it works fairly well, however, I'm trying to only fetch the numbers that are greater than or equal to 59 (that includes numbers like 59.1 and 59.0). I've tried several numeric regex combinations (the one below will not give me the right number, obviously, but just making a point), including:
while s/[^\,]+\,[^\,]+\,([^\,]+)\,^[0-9]{3}$/$1/g;
but none seem to work. Any ideas?

Answer 1

My first idea would be to split that line and then pick and choose
while (my $line = <IN>) {
my #nums = split ',\s*', $line;
print "$nums[2]\n" if $nums[2] >= $cutoff;
}
If you insist on doing it all in the regex then you may want to use /e modifier, so in the substitution part you can run code. Then you can test the particular match and print it there.

Answer 2

Assuming that the numbers can't reach 100 (three digits) you could use
[^\,]+\,[^\,]+\,\s*(59\.\d+|[6-9]\d\.\d+)\,
which uses your regex except for the capture group which captures the number 59 and it's decimals, or two digit numbers from 60-99 and it's decimals.
Regards
Edit:
To go above 100 you can add another alternative in the capture group:
[^\,]+\,[^\,]+\,\s*(59\.\d+|[6-9]\d\.\d+|[1-9]\d{2,}\.\d+)\,
which allows larger numbers (>=100.0).

Answer 3

Why do you use while? Is it possible to have more than one third column on a line? A simple if will work the same, comunicating the intent more clearly.
Also, if you want to extract, you don't need to substitute. Use m// instead of s///.
Regexes aren't the right tool to do numberic comparisons. Use >= instead:
print "Number: $1\n" if /[^\,]+\,[^\,]+\,([^\,]+)\,/
&& $1 >= 59

Answer 4

Assuming the line ends with a comma :
print foreach map{s/.+?(\d+.\d+),$/$1/;$_} ;
In case there might be someting after the rightmost comma :
print foreach map{s/.+?(\d+.\d+),[^,]*$/$1/;$_} ;
But i wouldn't use regexp in that case :
print foreach map{(split, ',')[-2]} ;

Answer 5

I would suggest not using a regex when split is a better tool for the job. Likewise - regex is very bad at detecting numeric values - it works on text based patterns.
But how about:
while ( <> ) {
print ((split /,\s*/)[2],"\n");
}
If you want to test a conditional:
while ( <> ) {
my #fields = split /,\s*/;
print $fields[2],"\n" if $fields[2] >= 59;
}
Or perhaps:
print join "\n", grep { $_ >= 59 } map { (split /,\s*/)[2] } <>;
map takes your input, and extracts the third field (returning a list). grep then applies a filter condition to every element. And then we print it.
Note - in the above, I use <> which is the magic file handle (reads files specified on command line, or STDIN) but you can use your filehandle.
However it's probably worth noting - 3 argument open with lexical file handles are recommended now.
open ( my $input, '<', 'file.txt' ) or die $!;
It has a number of advantages and is generally good style.