Proficiency in regular expression

Feel the symbol in the regular expression has a lot of, each time to use the time is not clear how to get, also often do not know exactly when to use the regular, so decided to summarize.

Regular expressions are made up of some ordinary characters and some meta-characters.

Ordinary characters include all printable and non-printable characters that are not explicitly specified as metacharacters. This includes all uppercase and lowercase letters, all numbers, all punctuation marks, and some other symbols.

"Nonprinting characters"

"Special character"--has a special meaning and needs to be escaped with "\".

Qualifier--The qualifier is used to specify how many times a given component of a regular expression must appear to satisfy a match. There are 6 types of * or + or? or {n} or {n,} or {n,m}.

Proficiency in regular expression