Problem with simple regex

Question

I have the following regular expression in a validation rule:

^[a-zA-Z0-9',!;?~>+&\"\-@#%*.\s]{1,1000}$

However, I can enter ====== which I believe should not be allowed.

My thoughts is that somehow the - could cause trouble if not properly escaped or something but this is way over my head.

Do you want to escape the * and the . as well? I'm not a regex expert, but I know those are special characters. — Starkey
– Starkey, Commented Oct 25, 2010 at 18:50
In firebug, this returns false. Are you sure it's the regex and not some glue code you have elsewhere? /^[a-zA-Z0-9',!;?~>+&\"\-@#%*.\s]{1,1000}$/.test("======") — Dave Aaron Smith
– Dave Aaron Smith, Commented Oct 25, 2010 at 19:07
Yeah, now that I test this, I'm getting false as well. Can you show your actual code? — Bill the Lizard
– Bill the Lizard, Commented Oct 25, 2010 at 19:15

codaddict · Accepted Answer · 2010-10-25 19:01:11Z

5

The regex you've shown us with the - escaped does not accept ===.
But if - is not escaped, === will be accepted. See this.

A - inside a regex is special and is used as range operator if it's not escaped and is surrounded by characters which participate as min and max in the range:

[a-z] matches any lowercase character.

[-az] matches either a - or a or z.

[az-] matches either a - or a or z.

[a\-z] matches either a - or a or z.

[a-c-d-f] matches a or b or c or - or d or e or f. The first and last - act as range operator but the one in the middle is treated literally.

In your case the = comes in the range "-@ and hence gets matched.

edited Oct 25, 2010 at 19:01

answered Oct 25, 2010 at 18:54

codaddict

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Comments

Dave Aaron Smith · Accepted Answer · 2010-10-25 18:49:42Z

1

matches on everything. You want

\.

answered Oct 25, 2010 at 18:49

Dave Aaron Smith

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2 Comments

Harmen Over a year ago

Sure? It's inside these brackets: []

Florian Over a year ago

I'm also pretty sure that this is the problem.

Bill the Lizard · Accepted Answer · 2010-10-25 18:50:01Z

1

The - will be interpreted as a range indicator. You need to put it either first or last within the [] brackets if you want to match a literal -.

answered Oct 25, 2010 at 18:50

Bill the Lizard

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Comments

MattAllegro · Accepted Answer · 2018-09-16 18:30:40Z

0

Your regex works fine for me but if I remove the escaping of - it matches =. I'm sure you are doing that.

edited Sep 16, 2018 at 18:30

MattAllegro

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answered Oct 26, 2010 at 6:21

user483085

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