What's the easiest way to get an equivalent to

问题:

I'm trying to grep through a bunch of files in nested subdirectories to look for regular expression matches; my regex requires negative lookbehind.

Perl has negative lookbehind, but as far as I can tell GNU grep doesn't support negative lookbehinds.

What's the easiest way to get an equivalent to GNU grep that supports negative lookbehinds?

(I guess I could write my own mini-grep in Perl, but that doesn't seem like it should be necessary. My copy of the Perl Cookbook includes source for tcgrep; is that what I should use? If so, where's the latest version? Don't tell me I have to type this entire program!)

回答1:

Use ack! Ack is written in Perl so it uses Perl's regex engine (by default).

The negative look-behind is ack "(?<!bad)boy" (per willert's comment)

回答2:

Thanks to a comment from other question. I've found that negative lookbehind is experimentally supported in grep with the -P/--perl-regexp option, so you may still not need to use a different tool if you prefer to keep using grep.

By the way, my preferred alternative to grep is grin (which is written in python).