. | Match any single character except newline. Can match newline in awk. |
* | Match any number (or none) of the single character that immediately precedes it. The preceding character can also be a regular expression; e.g., since . (dot) means any character, .* means "match any number of any character." |
^ | Match the following regular expression at the beginning of the line or string. |
$ | Match the preceding regular expression at the end of the line or string. |
[ ] | Match any one of the enclosed characters. A hyphen (- ) indicates a range of consecutive characters. A circumflex (^ ) as the first character in the brackets reverses the sense: it matches any one character not in the list. A hyphen or close bracket (] ) as the first character is treated as a member of the list. All other metacharacters are treated as members of the list (i.e., literally). |
{ n, m} | Match a range of occurrences of the single character that immediately precedes it. The preceding character can also be a metacharacter. { n} matches exactly n occurrences, { n,} matches at least n occurrences, and { n, m} matches any number of occurrences between n and m. n and m must be between 0 and 255, inclusive. |
\{ n, m\} | Just like { n, m} , above, but with backslashes in front of the braces. |
\ | Turn off the special meaning of the character that follows. |
\( \) | Save the pattern enclosed between \( and \) into a special holding space. Up to nine patterns can be saved on a single line. The text matched by the subpatterns can be "replayed" in substitutions by the escape sequences \1 to \9 . |
\ n | Replay the nth subpattern enclosed in \( and \) into the pattern at this point. n is a number from 1 to 9, with 1 starting on the left. See the following Examples. |
\< \> | Match characters at beginning (\< ) or end (\> ) of a word. |
+ | Match one or more instances of preceding regular expression. |
? | Match zero or one instances of preceding regular expression. |
| | Match the regular expression specified before or after. |
( ) | Apply a match to the enclosed group of regular expressions. |