Regex match everything up to first period

Question

Trying to get a lazy regex match of everything up until the first period of a sentence.

e.g. Just want to get "jack and jill." from this sentence:
"jack and jill. went up the hill. to fetch a pail."

/.+\./ matches the whole sentence (example)
/(.+?\.)/ matches each instance (example)

Is there a way to just match the first instance?

Like what @revo has answered, it could also do without the parentheses [demo](https://regex101.com/r/tzaQhs/1/), unless you somehow want the match to be in a capture group? — swlim, Jun 01 '17 at 17:51
Possible duplicate of [Return first match of Ruby regex](https://stackoverflow.com/questions/519572/return-first-match-of-ruby-regex) — revo, Jun 01 '17 at 18:10

score 31 · Accepted Answer · edited Jan 20 '18 at 21:58

31

/^([^.]+)/

Let's break it down,

^ is the newline anchor
[^.] this matches any character that's not a period
\+ to take until a period

And the expression is encapsulated with () to capture it.

edited Jan 20 '18 at 21:58

Sebastián Palma

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answered Jun 01 '17 at 17:51

Matthew Brock Carey

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*"^ is the beginning of string anchor"*: No it's wrong, in Ruby `^` matches the start of a line (not of the string). The anchor for the start of the string is `\A` – Casimir et Hippolyte Jun 01 '17 at 17:57
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Note that when `.` appears within square brackets, it does not need to be escaped. `[\.]` is the same as `[.]`. (And the negating carat doesn't change this.) – CAustin Jun 01 '17 at 18:01
You're correct, I never have a reason to use \A so the concept blends together for me. Updated to reflect this. – Matthew Brock Carey Jun 01 '17 at 18:01

score 2 · Answer 2 · answered Jun 01 '17 at 18:07

If you only want the first occurrence, do not choose the scan method that returns all results in the string. You can use the match method that returns a MatchData instance, but you can also simply write:

> "jack and jill. went up the hill. to fetch a pail."[/.+?\./]
 => "jack and jill."

score 1 · Answer 3 · answered Jun 01 '17 at 20:01

I would be inclined to use a regex, but there are other options.

str = "jack and jill. went up the hill. supposedly to fetch a pail of water."
str[0..i] if i = str.index('.')
  #=> "jack and jill."

str = "three blind mice"
str[0..i] if i = str.index('.')
  #=> nil

Regex match everything up to first period

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