Match any number (or none) of the single character that immediately precedes it. The preceding character also can be a regular expression (e.g., since . (dot) means any character, .* means match any number of any character -- except newlines).

Match the beginning of the line or string.

Match 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.

Match anything except enclosed characters.

Match a range of occurrences of the single character that immediately precedes it. The preceding character also can be a regular expression. \{n\} matches exactly n occurrences, \{n,\} matches at least n occurrences, and \{n,m\} matches any number of occurrences between n and m.

Like \{n,m\}. Available in grep by default and in gawk with the -Wre-interval option.

Turn off the special meaning of the character that follows.

Save the matched text enclosed between \( and \) in a special holding space. Up to nine patterns can be saved on a single line. They can be "replayed" in the same pattern or within substitutions by the escape sequences \1 to \9.

Reuse matched text stored in nth \( \).

In egrep and gawk, save the matched text enclosed between \( and \) in a holding space to be replayed in substitutions by the escape sequences \1 to \9.

Match the beginning (\<) or end (\>) of a word.