Regular Expression metacharacters in Shell

1. '.' Matches any character

2. '*' Specifies that * can be used repeatedly for any number of times.

3. '^' Starts with a string

4. '$' String end

5. '. *' Any number of characters

6. '\' Escape Character

7. '[...]' Matches any character

8. '[^...]' Does not match any character.

9. '\(.... \) 'Indicates matching characters, which are subsequently referenced by escape sequences, for example \ (grep \). * \ 1, matching two grep characters with any number in the middle

10. '\ N' repeats the nth pattern in \ (... \).

11. The X \ {M, N \} interval expression matches the number of occurrences of the X character. X \ {n \} indicates that X appears n times, and X \ {M, \} indicates that X appears at least m times,

    X \ {M, N \} indicates that at least M appears, at most N times

12. '\ <... \>' Matches the start and end of a word.