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).
来源:https://stackoverflow.com/questions/2490007/whats-the-easiest-way-to-get-an-equivalent-to-gnu-grep-that-supports-negative-l