Linux regular expression

Metacharacter Description

. Matches any single character. For example the regular expression r.t would match the strings rat, rut, r t, but not root.
$ Matches the end of a line. For example, the regular expression weasel$ would match the end of the string "He's a weasel" but not the string "They are a bunch of weasels."
^ Matches the beginning of a line. For example, the regular expression ^When in would match the beginning of the string "When in the course of human events" but would not match "What and When in the" .
* Matches zero or more occurences of the character immediately preceding. For example, the regular expression .* means match any number of any characters.
\ This is the quoting character, use it to treat the following character as an ordinary character. For example, \$ is used to match the dollar sign character ($) rather than the end of a line. Similarly, the expression \. is used to match the period character rather than any single character.
[ ] Matches any one of the characters between the brackets
For example, the regular expression r[aou]t matches rat, rot, and rut, but not ret. Ranges of characters can specified by using a hyphen. For example, the regular expression [0-9] means match any digit. Multiple ranges can be specified as well. The regular expression [A-Za-z] means match any upper or lower case letter. To match any character except those in the range, the complement range, use the caret as the first character after the opening bracket. For example, the expression [^269A-Z] will match any characters except 2, 6, 9, and upper case letters.
\< \\> Matches the beginning (\<) or end (\>) or a word. For example, the matches on "the" in the string "for the wise" but does not match "the" in "otherwise". NOTE: this metacharacter is not supported by all applications.
\( \) Treat the expression between \( and \) as a group. Also, saves the characters matched by the expression into temporary holding areas. Up to nine pattern matches can be saved in a single regular expression. They can be referenced as \1 through \9.
| Or two conditions together. For example (him|her) matches the line "it belongs to him" and matches the line "it belongs to her" but does not match the line "it belongs to them." NOTE: this metacharacter is not supported by all applications.
+ Matches one or more occurences of the character or regular expression immediately preceding. For example, the regular expression 9+ matches 9, 99, 999. NOTE: this metacharacter is not supported by all applications.
? Matches 0 or 1 occurence of the character or regular expression immediately preceding.NOTE: this metacharacter is not supported by all applications.
\{i\}
\{i,j\} Match a specific number of instances or instances within a range of the preceding character. For example, the expression A[0-9]\{3\} will match "A" followed by exactly 3 digits. That is, it will match A123 but not A1234. The expression [0-9]\{4,6\} any sequence of 4, 5, or 6 digits. NOTE: this metacharacter is not supported by all applications.