CODEWITHSUNDEEP
regexstring
Kingamere
Kingamere

Reputation: 10122

regex, match a substring within a string

I want to a capture a string with this regex:

^([\d]_[a-z|A-Z]+_test)$

So it would capture something like: 1_mytest_test

However, if the string is within another string like:

results.1_mytest_test.=fail, more info

There is no match.

I thought the ^ and $ would demarcate the beginning and end of the string that I am looking for, right?

Upvotes: 5

Views: 53152

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626738

You should remove the ^/$ anchors, and you need no | inside the character class if you do not need to match a literal | with the regex:

\d_[a-zA-Z]+_test

See regex demo

The ^ is a start of string anchor, and $ is an end of string anchor, thus, they "anchor" the string you match at its start and end.

As for |, a character class matches a single character. [a-zA-Z] matches 1 letter. No need in the alternation operator | here since it is treated literally (i.e. the [a-zA-Z|] will match | symbol in the input string).

Just FYI: in many cases, when you need something to be matched inside a larger string, you need to use word boundaries \b to match whole words:

\b\d_[a-zA-Z]+_test\b

However, people often have non-word characters in patterns, then you'd be safer with look-arounds (not sure your engine supports look-behind, but here is a version for, say, PCRE):

(?<!\w)\d_[a-zA-Z]+_test(?!\w)

Upvotes: 8

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