Beefy Boxes and Bandwidth Generously Provided by pair Networks
Problems? Is your data what you think it is?
 
PerlMonks  

Re^3: regex: negative lookahead

by kennethk (Abbot)
on Dec 05, 2011 at 16:38 UTC ( #941894=note: print w/ replies, xml ) Need Help??


in reply to Re^2: regex: negative lookahead
in thread regex: negative lookahead

The difference is a lookahead versus a lookbehind. If you ignore the lookahead/lookbehind because they are zero width (don't consume characters), you would expect /^($start(\w+(,\s)?)+)$/ to grab an entire string between start and finish. When you get to the part of the regular expression where you have your assertion, the cursor is here:

log4j.rootLogger=INFO, FILE, SYSLOG ^
If you look ahead of this position, there is nothing, which clearly passes the negative lookahead check. The offending string is behind your position, thus you need a negative lookbehind.


Comment on Re^3: regex: negative lookahead
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://941894]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others rifling through the Monastery: (4)
As of 2015-07-03 20:55 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (56 votes), past polls