RegexOne

http://regexone.com/

http://regexone.com/lesson/optional_characters?

http://regexone.com/lesson/capturing_groups

Task Text Capture Groups
Capture file_record_transcript.pdf file_record_transcript Success
Capture file_07241999.pdf file_07241999 Success
Skip testfile_fake.pdf.tmp

^(file.+)\.pdf

http://regexone.com/lesson/nested_groups?

Task Text Capture Groups
Capture Jan 1987 Jan 1987 1987
Capture May 1969 May 1969 1969
Capture Aug 2011 Aug 2011 2011

(\D+(\d+))

http://regexone.com/lesson/more_groups

1280x720 提取出1280 720

((\d+)\D(\d+))

http://regexone.com/lesson/conditionals

Task Text
Match I love cats
Match I love dogs
Skip I love logs
Skip I love cogs

I love (cats|dogs)