Regex to include strings that start with @ but not in the middle of string?

Question

I'm trying to match @username similar to twitter. The regex I'm using right now: "([@])(\S+)" works decently well for this.

However limitations are as follows test@test.com matches test.com

Now I want to completly exclude test@test.com

However, some of my users have usernames test@test.com and want to include them if they actually have an @ in front of that email username.

So @test@test.com should match

Summary: Needs to match:

@username

@test

@test@test.com

Do not want to match:

test@test.com

Answer 1

I'd recommend using a negative lookbehind, eg:

(?<!\S)@(\S+)

This will not include any possible space before the @foo, so you can replace it without issue.

Answer 2

Making as an answer, you don't want to check for @ in middle of the text, but it needs a space in front, so use (\s|^)+([@])(\S+)

Answer 3

^@.* The above regular expression matches what you are looking for

Answer 4

The regex would look something like this: ^@.* The ^ will anchor you to the start of the line or the string. Be sure to check out OverAPI Regex, their cheat sheets are very nice.