CODEWITHSUNDEEP
.netregex
JA1
JA1

Reputation: 568

Regex Word boundary confusion

From what I read if, I want to capture specific words that I could use word boundaries.

I have the following information

First: 12345Z Apr 16 Something WORD: ABC Notification #1234 Key1 Key2 Key3 Key4
Second: 12345Z Apr 16 Something WORD: ABC Notification #1234 Key5 Key3 Key6
Third: 12345Z Apr 16 Something WORD: ABC Notification #1234 Key7 Key6

I used the following regex and it will only match Key7 when I need to match Key3 Key4 Key6 Key7

(?<=#\d{4}\s)(\b(Key3|Key4|Key6|Key7)\b)

Upvotes: 2

Views: 540

Answers (2)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627468

The issues is that your regex does not let anything between the #+4 digits and the keys you are interested in. You can easily fix it by adding an optional (?:\s+\w+)* pattern to the lookbehind that will match zero or more sequences of 1+ whitespace and 1+ word characters:

(?<=#\d{4}(?:\s+\w+)*)\s*\b(Key3|Key4|Key6|Key7)\b
          ^^^^^^^^^^^

See the regex demo, declare with the verbatim string literal in C# (or use as is in VB.NET) and use with Regex.Matches.

A C# demo:

var strs = new List<string> { "First: 12345Z Apr 16 Something WORD: ABC Notification #1234 Key1 Key2 Key3 Key4",
"Second: 12345Z Apr 16 Something WORD: ABC Notification #1234 Key5 Key3 Key6",
"Third: 12345Z Apr 16 Something WORD: ABC Notification #1234 Key7 Key6"};
foreach (var s in strs) {
    var result = Regex.Matches(s, @"(?<=#\d{4}(?:\s+\w+)*)\s*\b(Key3|Key4|Key6|Key7)\b")
        .Cast<Match>()
        .Select(m => m.Value)
        .ToList();
    foreach (var e in result)
        Console.WriteLine(e);
}

Upvotes: 1

Tim007
Tim007

Reputation: 2557

Try this

(?:#\d{4}|\G)\s(\b(?:Key3|Key4|Key6|Key7)\b)

Regex demo

or this

(?:#\d{4}|\G) \b(?:(Key3|Key4|Key6|Key7)|\w+)\b

Regex demo

Explanation:
(?: … ): Non-capturing group sample
\: Escapes a special character sample
|: Alternation / OR operand sample
\G: Beginning of String or End of Previous Match sample
\s: "whitespace character": space, tab, newline, carriage return, vertical tab sample
( … ): Capturing group sample

Upvotes: 1

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