Re: Best way to match a file.

[Athanasius]

Three quick observations:

1. You can make the match more efficient by anchoring it to the end of the string: m/(.{10,}XYZQW.*\.csv$)/i

2. .{10,}.* says “match at least 10 characters, followed by 0 or more characters”. It is equivalent to .{10,} by itself, i.e., the additional .* is redundant.

3. The /g modifier is also redundant here.

Hope that helps,

[Anonymous Monk]

That’s good, but if in a different condition could it match both file names and with different extensions in:

print "\n  REMOVED $file\n\n" if $file =~ m/(.{10,}XYZQW|KMHYT.*\.csv|
+\.txt)/i;

Thanks

[Athanasius]

Yes, but you need to group the alternations, and for efficiency, the grouping should be non-capturing:

#! perl
use strict;
use warnings;

for (
       'ASQWERFD.YYxxxx.W12345.XYZQW.D072413.csv',
       'ASQWERFD.YYxxxx.W12345.XYZQW.D072413.txt',
       'ASQWERFD.YYxxxx.W12345.XYZQW.D072413.dat',
       'ASQWERFD.YYxxxx.W12345.KMHYT.D072413.csv',
       'ASQWERFD.YYxxxx.W12345.XYZQA.D072413.csv',
    )
{
    if (/ .{10,} (?: XYZQW | KMHYT) .* \. (?: csv | txt) $ /ix)
    {
        print "Matched  $_\n";
    }
    else
    {
        print "Ignoring $_\n";
    }
}

Output:

11:57 >perl 673_SoPW.pl
Matched  ASQWERFD.YYxxxx.W12345.XYZQW.D072413.csv
Matched  ASQWERFD.YYxxxx.W12345.XYZQW.D072413.txt
Ignoring ASQWERFD.YYxxxx.W12345.XYZQW.D072413.dat
Matched  ASQWERFD.YYxxxx.W12345.KMHYT.D072413.csv
Ignoring ASQWERFD.YYxxxx.W12345.XYZQA.D072413.csv

11:57 >

On grouping, see Regular Expressions:

WARNING: Once Perl sees that you need one of $&, $`, or $' anywhere in the program, it has to provide them for every pattern match. This may substantially slow your program. Perl uses the same mechanism to produce $1, $2, etc, so you also pay a price for each pattern that contains capturing parentheses. (To avoid this cost while retaining the grouping behaviour, use the extended regular expression (?: ... ) instead.)

Note that I’ve also used /x for improved readability.

Hope that helps,