正则表达式查找以特定字符开头的特定单词

Question

Using Regex, I need to find a word within a string that starts with specific char. The word must be alphanumeric, but may contain underscore (_) within the word. underscore at the beginning and end of the word is not acceptable.

For example I have the following string.

@word1 Message @@ message @ message @word2_ message @word#3 @_word4 mesagge @word_5

The result should be:

@word1 @word_5

Thanks.

Answer 1

Use regex pattern

(?:^|(?<=\s))@(?!_)\w+(?<!_)(?:(?=\s)|$)

or

(?:^|(?<=\W))@(?!_)\w+(?<!_)(?:(?=\W)|$)

depends what you need/want to have infront/behind...

For example if @word1 in @word_5 @word1. @word#2 @word*3 @word_5 @word1. @word#2 @word*3 should match, considering dot . as separator or end of sentence.

Answer 2

This will work - the bounds (lines 1 and 3) are fairly heavy because \\b , the word boundary, won't work here since you don't want to match "@word#3", and the "#" character after "d" triggers a word boundary.

(?<=\s|^)
    @(?!_)\w+(?<!_)
(?=\s|$)

Answer 3

This Regex will do it!

(?<=(^|\s))@([a-zA-Z0-9]{1}\w*[a-zA-Z0-9]|[a-zA-Z0-9]{1})(?=(\s|$))

It also matches single letter