One liner

finds patterns like ..(phl1|aus2) in the log, trying to find all host names.

Find all string matches with dir, one or more subdir, file name with optional extension. Common example with all capturing groups included: C://ProgramFiles/MyDir1/myDir2/file.ext

Find all string matches with dir, one or more subdir, file name with optional extension. Common example with all capturing groups included: ../../dir/SubDir1/SubDir2/file.ext ...

Validate Brazilian monetary values. Can be easily addapted to other countries.

For our own format with real ip (from proxy forwarded for header) and upstream response times: log_format combined_w_timing '$http_x_forwarded_for [$remote_addr] - $remote_user [$time_local] ' '"$request" $status $body_bytes_sent ' '"$http_referer" "$http_use...

Test of acceptable ranks regex.