The question is about PERL regular expressions.

I need to match a string that

• starts with < and ends with >
• must contain number [0-9]
• can optionally contain \s (i.e. space) and ,
• any number of characters
• order is random

This pattern does not discriminate between mandatory and optional characters:

/<[0-9,\s] >/

and will match:

<9>
<9,10>
<9, 10>

which is what I want, but also these two that I dont want:

< >
<,>

So, how to set a PERL regex that will find a match that will always contain 0-9 and can optionally contain \s, ?

CodePudding user response：

how to set a PERL regex that will find a match that will always contain 0-9 and can optionally contain \s,:

Verbatim for this requirement, you can use this regex:

/<[\d,\h]*\d[\d,\h]*>/

Which stands for:

• <: Match a <
• [\d,\h]*: Match 0 or more digits or whitespace or comma
• \d: Match a digit
• [\d,\h]*: Match 0 or more digits or whitespace or comma
• >: Match a >

RegEx Demo

CodePudding user response：

You can use

<\d (?:,\s*\d )*>

See the regex demo. Details:

• < - a < char
• \d - one or more digits
• (?:,\s*\d )* - zero or more occurrences of a ,, zero or more whitespaces and then one or more digits
• > - a > char.