Regular Expression to find Email in a Text

Question

I am using PHP to find e-mail address in a given text. My current regex is:

'/([\w+\.]*\w+@[\w+\.]*\w+[\w+\-\w+]*\.\w+)/is'

It is consuming a lot of CPU resources. Is there any optimized and low resource utilized ( i.e CPU ) RegEx for finding a Valid E-mails in a given text.

Possible duplicate of [Using a regular expression to validate an email address](http://stackoverflow.com/questions/201323/using-a-regular-expression-to-validate-an-email-address) — randers, May 16 '16 at 08:14
use the regex mentioned by @RAnders00 or you need to use atomic groups or possessive quantifiers,otherwise there will be too much of backtracking __(your regex is incorrect though)__ — rock321987, May 16 '16 at 08:18

score 1 · Answer 1 · edited Jun 20 '20 at 09:12

1

This

/^[^@]+@[a-z]+(\.[a-z]+)+$/

is better than yours.

Why?

Let's say we want to test this email: foo@bar.co.uk

In case of success my regexp perform 14 steps to find the solution.
Yours in 22 steps.

BUT THE BIGGEST DIFFERENCE IS IN NON-MATCHING CASE

Let's say we want to test this email: foo@bar.co.uk.foo.

My regex performs 31 steps and fails

Yours (that should be modified with ^ and $ delimiters, otherwise it will match this as a good one) performs 292 steps and fails!

edited Jun 20 '20 at 09:12

Community

1
1

answered May 16 '16 at 08:17

DonCallisto

29,419
9
72
100

What application you are using to check your regex? Can you tell me, so i can also check where I am making mistake. – Siddharth sharma May 16 '16 at 08:25
@Siddharthsharma: use regex101.com – DonCallisto May 16 '16 at 08:27

score 1 · Answer 2 · answered May 16 '16 at 08:29

1

Sometimes trading off some false positives for better performance is desirable:

/[^ @]*@[^ ]*/

This should be quite fast. It will also match stuff like __imp__MessageBoxW@16, but such constructs aren't that common in normal text.

answered May 16 '16 at 08:29

a3f

8,517
1
41
46

keziah · Answer 3 · 2016-05-16T08:19:52.083

0

Try this

/[-\d\w\W]+@[-\d\w.+_]+.\w{2,4}/

Matches:

hello.world@example.com my_guru@lcoalhost guy.31@site.co, etc...

Tested at http://regexr.com/

edited May 16 '16 at 08:19

answered May 16 '16 at 08:13

keziah

564
1
6
24

e-mail contains symbols also. This regex will not check for that. – Siddharth sharma May 16 '16 at 08:15
but not these Characters ! # $ % & ' * + - / = ? ^ _ ` { | } ~ – Siddharth sharma May 16 '16 at 08:21
please refer to http://stackoverflow.com/questions/2049502/what-characters-are-allowed-in-email-address – keziah May 16 '16 at 08:24
Sorry for that. You edited your regex. Now it's working. Thanks – Siddharth sharma May 16 '16 at 08:27
2

`[-\d\w\W]` (equal to `[\w\W]`) matches all characters there are in the world. Unescaped `.` matches any character but a newline. Also, testing a regex that should work in PCRE in a JavaScript compatible regex tester is not the best idea. – Wiktor Stribiżew May 16 '16 at 08:32

Regular Expression to find Email in a Text

3 Answers3

Why?

BUT THE BIGGEST DIFFERENCE IS IN NON-MATCHING CASE