exclude underscore from alpha numeric regex

Question

I want use \\w regex for to allow alpha numeric but I don\'t want underscore _ to be part of it. Since _ is included in \\w

Answer 1

Your proposed solution:

(/^roger\w{2,3}[0-9a-z]/i)

Means:

\w{2,3} -- 2 or 3 alphanumeric, including the _

[0-9a-z] (with the /i) -- a single character that is alphanumeric, not including the _

I didn't see any mention of the acceptable 3 alphanumerics at the beginning. Does that belong?

Both "roger54" and "roger4a" should fail this because the above regex requires at least three characters following "roger." Likewise, "roger_a" would succeed because "_" passes \w{2,3} (specifically \w{3}).

Your request sounded like you wanted more of one of these:

/^roger[0-9a-z]+/i
/^roger[0-9a-z]*/i

that is, "roger" (case insensitive) followed by one or more (+) or zero or more (*) letters and/or numbers.

Answer 2

You could try something like:

[^_\W]+

Answer 3

Assuming the identifier must begin with an alpha character, and then may contain any number of alpha or numeric, I would do this:

my $string = 'roger54a';
print "Match\n" if $string =~ m/\A\p{alpha}[\p{alpha}\p{Number}]*\z/;

That anchors to the start and end of the string, precluding any characters that don't match the specific set of a single alpha followed by any quantity of alpha and numerics.

Update: I see tchrist just gave a great explanation of the Unicode properties. This answer provides the context of a full regexp.

If you wanted the leading 'alphas' to be two or three digits followed by alpha-numeric, just add the appropriate quantifier:

$string =~ m/\A\p{alpha}{2,3}[\p{alpha}\p{Number}]*\z/

Update2: I see a stronger definition of what you're looking for in a comment to one of the answers here. Here's my take on it after seeing your clarification:

m/\Aroger[\p{alpha}\p{Number}]{2,3}\z/

Answer 4

I was trying to find a solution to this also and this solution did not work for me in C# when trying to do a regex replace. In case someone else is searching:

c# Regex.Replace [^\w ] that also removes underscores?

This is what I use in C#:

cleaned_string = Regex.Replace(input_string, @"[_]+|[^\w]+]", "");

If you want to keep spaces:

cleaned_string = Regex.Replace(input_string, @"[_]+|[^\w\s]+", "");

Answer 5

• A numeric code point is \pN or \p{Number}.
• A digit code point is \d, \p{digit}, \p{Nd}, \p{Decimal_Number}, or \p{Numeric_Type=Decimal}.
• An alphabetic code point is \p{alpha} or \p{Alphabetic}. It includes all \p{Digit}, \p{Letter}, and \p{Letter_Number} code points, as well as certain \p{Mark} and \p{Symbol} code points.
• A programming-word code point is \w, or [\p{Alphabetic}\p{Digit}\p{Mark}\p{Connector_Punctuation}].

An alphanumeric code point by the strictest definition is consequently and necessarily [\p{Alphabetic}\p{Number}], typically abbreviated [\p{alpha}\pN].