Regex to match only the first line?

Question

Is it possible to make a regex match only the first line of a text? So if I have the text:

This is the first line.
This is the second line. ...

It would match "This is the first line.", whatever the first line is.

Answer 1

that's sounds more like a job for the filehandle buffer.

You should be able to match the first line with:

/^(.*)$/m

(as always, this is PCRE syntax)

the /m modifier makes ^ and $ match embedded newlines. Since there's no /g modifier, it will just process the first occurrence, which is the first line, and then stop.

If you're using a shell, use:

head -n1 file

or as a filter:

commandmakingoutput | head -n1

Please clarify your question, in case this is not wat you're looking for.

Answer 2

In case you need the very first line no matter what, here you go:

 \A.*

It will select the first line, no matter what.