Match a pattern only once

问题

I have a string

foo-bar-bat.bla

I wish to match only foo

My flawed pattern matches both foo and bar

\w+(?=-.*\.bla)

How do I discard bar? Or maybe even better, how could I stop matching stuff after foo?

回答1:

You could use the following pattern (as long as your strings are always formatted the way you said) :

^\w+(?=-.*\.bla)

Edit live on Debuggex

The ^ sign matches the beginning of the string. And thus will take the very first match of the string.

The ?= is meant to make sure the group following is not captured but is present.

回答2:

^[^-]+

The starting ^ means to start matching from the beginning of the string. The charactergroup [^-] means to search for anything that is not a dash. The + means that the charactergroup should be match a character one or multiple times.

回答3:

The ".*" part of your expression matches "bar."

^\w+(?=-.*)

This expression reads as "At the start of a string, at least one character followed by (but not includeded in the match) a DASH followed by anything"

^ \w+ (?=-.*)
|  |    |
|  |   matches "-bar-bat.bla"
|  matches "foo"
start of string

来源：https://stackoverflow.com/questions/15392753/match-a-pattern-only-once