I want to make a regex that recognize some patterns and some not.

_*[a-zA-Z][a-zA-Z0-9_][^-]*.*(?<!_)

The sample of patterns that i want to recognize:

a100__version_2
_a100__version2

And the sample of patterns that i dont want to recognize:

100__version_2
a100__version2_
_100__version_2
a100--version-2

The regex works for all of them except this one:

a100--version-2

So I don't want to match the dashes.

I tried _*[a-zA-Z][a-zA-Z0-9_][^-]*.*(?<!_) so the problem is at [^-]

CodePudding user response：

You could write the pattern like this, but [^-]* can also match newlines and spaces.

To not match newlines and spaces, and matching at least 2 characters:

^_*[a-zA-Z][a-zA-Z0-9_][^-\s]*$(?<!_)

Regex demo

Or matching only word characters, matching at least a single character repeating \w* zero or more times:

^_*[a-zA-Z]\w*$(?<!_)

• ^ Start of string
• _* Match optional underscores
• [a-zA-Z] Match a single char a-zA-Z
• \w* Match optional word chars (Or [a-zA-Z0-9_]*)
• $ End of string
• (?<!_) Assert not _ to the left at the end of the string

Regex demo

CodePudding user response：

To exclude dashes from the regex, you can use the negative lookahead assertion (?!-) after the [^-] character class. This will make sure that the regex does not match any dashes after the [^-] character class.

Here's an updated version of the regex that excludes dashes:

[a-zA-Z]a-zA-Z0-9_.*(?<!)

This regex should match the patterns you want to recognize, and exclude the patterns you don't want to recognize.

Here are some examples of how this regex will work:

a100__version_2   // matches
_a100__version2   // matches
100__version_2    // does not match
a100__version2_   // does not match
_100__version_2   // does not match
a100--version-2   // does not match