RegEx for capturing a word in between = and ;

Question

I want to select word2 from the following :

word2;word3

word2 that is between ; and start of the line unless there is a = in between. In that case, I want start from the = instead of the start of the line like word2 from

word1=word2;word3

I have tried using this regex

(?<=\=|^).*?(?=;)

which select the word2 from

word2;word3

but also the whole word1=word2 from

word1=word2;word3

Answer 1

You can use an optional group to check for a word followed by an equals sign and capture the value in the first capturing group:

^(?:\w+=)?(\w+);

Explanation

• ^ Start of string
• (?:\w+=)? Optional non capturing group matching 1+ word chars followed by =
• (\w+) Capture in the first capturing group 1+ word chars
• ; Match ;

See a regex demo

In .NET you might also use:

(?<=^(?:\w+=)?)\w+(?=;)

Regex demo | C# demo