On 3/20/06, stu meacham <[EMAIL PROTECTED]> wrote:
> I would like to modify a file 'in place' at the command line with regexes.
> The file changes daily and is messy. Can one negate a regex itself as
> opposed to a class of regular expressions? If I could remove everything but
> that selected by m/\d{2}\t\d{2}\t\d{2}/g life would be better as I know it.
> Thanx
>
> --
Stu,
The short answer is "not really," but it depends on your data, and
what, exactly, you want to do. Do you want to remove lines that don't
match? Do you want to delete just the parts of the line that don't
match? Is your data delimited in some way and you want to remove all
fields but one? There are several (at least) ways to approach this,
depending on the situation. Here are some thoughts to get you
started, though:
in list context, m// returns an array of capturing paren matches, so
something like:
@matched = /(\d{2}\t\d{2}\t\d{2})/g; print "@matched\n";
might work for you. You could also try something like:
s/.*?(\d{2}\t\d{2}\t\d{2}).*?(?!\d{2}\t\d{2}\t\d{2})/$1/g
look for (?!) and "zero-width negative lookahead" in perlre. And of
course if your data can be conveniently split into fileds, check out
the -a flag in perlrun and grep() in perlfunc.
HTH,
-- jay
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