Regular expression meta-character collation

Basic Regular Expressions

Match characters:

. : matches any single character.

[]: matches characters within a specified range

[::] : Character Set

[: space:] Space character

[: Lower:] Lowercase Letters

[: Upper:] Uppercase Letters

[: Alpha:] uppercase and lowercase letters

[:d igit:] Digital

[: alnum:] numbers and uppercase and lowercase letters

[^]: matches a character outside a specified range

Number of matches:

*  : matches the preceding character of the symbol any time.

.* : matches any character any time.

\?: match its first character 1 Times or 0 times.

Location anchoring:

^ : The character followed must be at the beginning of the line.

$: the preceding character must be at the end of the line.

^$: blank line.

\b or \< : The character followed must be the word header.

\b or \>: The preceding character must be the tail of the word.

Group:

\(\): group content as a whole, can appear any time eg: \ (root\)

back reference:

\ 1: The first opening parenthesis and the corresponding closing parenthesis contain the contents.

\2: ....

\3: ....

Extending regular Expressions

Character Matching:

. :

[] :

[::]:

[^]: the above are all the same as the basic regular expression

Number of matches:

*:

?: above with the basic regular expression

+: match its first character at least 1 times, with \ (1,\) .

{m,n}: the match period before the character at least m times, the more N times.

Anchor Position:

The same basic regular expression.

Group:

(): don't need \ .

| : Or, a|b:a or b,c| Cat:c or Cat.

Regular expression meta-character collation