re正则表达式13_review of regex symbols

Review of Regex Symbols

This chapter covered a lot of notation, so here’s a quick review of what you learned:

• The ? matches zero or one of the preceding group.

• The * matches zero or more of the preceding group.

• The + matches one or more of the preceding group.

• The {n} matches exactly n of the preceding group.

• The {n,} matches n or more of the preceding group.

• The {,m} matches 0 to m of the preceding group.

• The {n,m} matches at least n and at most m of the preceding group.

• {n,m}? or *? or +? performs a nongreedy match of the preceding group.

• ^spam means the string must begin with spam.

• spam$ means the string must end with spam.

• The . matches any character, except newline characters.

• d, w, and s match a digit, word, or space character, respectively.

• D, W, and S match anything except a digit, word, or space character, respectively.

• [abc] matches any character between the brackets (such as a, b, or c).

• [^abc] matches any character that isn’t between the brackets.