How to set the first character via RegEx?

Question

The first character can be anything except '='.

I made the following RegEx:

[^=].

"ab", "b2" etc will pass. "=a" will not.

But the thing is, I also want to accept an empty character:

"a" should also be accepted. How can I do that?

Update

Sorry, the language is C#

You might wonder why I'm doing it. I have a URL RegEx

(?!=)((www.|(http|https|ftp)\://)[.a-z0-9-]+.[a-z0-9\/_:@=.+?,##%&~-]*[^.|\'|# |!|(|?|,| |>|<|;|)])

but I don't want the URL to be parsed if it's right after the '=' character.

Answer 1

Try a negative lookahead:

^(?!=)

^ matches the start of the input, and (?!...) is a negative look ahead. It also matches an empty string.

Answer 2

Anchor to the beginning and end, and make the whole thing optional.

^(?:[^=].*)?$

Answer 3

Couldn't you just use ^= and act if there is no match in your code?

Answer 4

Try using this one:

^[^=].*

Answer 5

If this is the only constraint in your regex, you should try to use the API provided by the language you're working with to get the first character of a string.

String s = "myString";
if(s.Length == 0 || s[0] != '=')
    //Your code here

---

If you really want a regex look at @Bart solution.

Here is an alternative without look ahead /^([^=]|$)/

^        <- Starts with
(        <- Start of a group
  [^=]     <- Any char but =
  |        <- Or
  $        <- End of the match
)        <- End of the group

Answer 6

You don't need RegEx. There is String.StartsWith...

if ( ! theString.StartsWith("=") ) {
   ...