Regular expression to find two strings anywhere in input

Question

How do I write a regular expression to match two given strings, at any position in the string?

For example, if I am searching for cat and mat

Answer 1

You can try:

\bcat\b.*\bmat\b

\b is an anchor and matches a word boundary. It will look for words cat and mat anywhere in the string with mat following cat. It will not match:

Therez caterpillar on the mat.

but will match

The cat slept on the mat in front of the fire

If you want to match strings which have letters cat followed by mat, you can try:

cat.*mat

This will match both the above example strings.