CODEWITHSUNDEEP
c#regex
Sri Reddy
Sri Reddy

Reputation: 7012

Regex match certain string and ignore if it starts with some pattern

I have a following regular expression that I use in C# code that tries to match save some followed by some word and delete some followed by some word in a file.

\bsave\ssome\b\s[^\s]+|\bdelete\ssome\b\s[^\s]+

This works as expected. Now, I wanted to exclude those from the match that has a pattern like - save some and - delete some.

I tried using the following but it didn't work. In the expression below I just used the expression to ignore - save some Appreciate any help. (?!-\s\bsave\ssome\b\s[^\s])(\bsave\ssome\b\s[^\s]+|\bdelete\ssome\b\s[^\s]+)

The demo is here

Upvotes: 3

Views: 1802

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626738

You need to use a negative look-behind and group the pattern:

(?<!-\p{Zs}*)(?:\bsave\ssome\b\s[^\s]+|\bdelete\ssome\b\s[^\s]+)
^^^^^^^^^^^^  ^                                                ^

See regex demo

The (?<!-\p{Zs}*) lookbehind fails a match if the save/delete some is preceded with - followed by zero or more spaces (use + if there must be at least one). I used \p{Zs} to only match horizontal whitespace. If you want to match newlines, use \s.

A contracted regex version:

(?<!-\s*)\b(save|delete)\ssome\b\s\S+

Use the Explicit Capture flag with it. Since \ssome\b\s\S+ is common for both alternatives, you can move the end of the group to just include save and delete.

C#:

var rx = @"(?<!-\s*)\b(save|delete)\ssome\b\s\S+";

Upvotes: 3

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