17 Regular Expressions for Search and Replacement Operation

Characters for creating regular expressions:

Character(s)	Match
^	Matches the beginning of a line.
$	Matches the end of a line.
.	Matches any single character (like ? in filenames).
.*	Matches any group of zero or more characters (. matches any character and* matches zero or more of the previous character).
\<	Matches the beginning of a word.
\>	Matches the end of a word.
[ ]	Matches any character specified within the brackets; for example, [a-z] matches any alphabetic character.
\s, \S	Matches any whitespace character: space, a newline, a tab, a carriage return, a formfeed, or a backspace;\S matches any character except whitespace.
\d, \D	Matches any single digit, 0-9;\D matches any character but a digit.
\w, \W	Matches any “word” character (upper- and lowercase letters, digits, and the underscore character);\W matches any character but these.

Mastering Regular Expressions by Jeffrey Friedl (O’Reilly)

Regular expression search commandsegular expression search commands:

Keystrokes	Command name	Action
C-M-s Enter Edit → Search → Regexp Forward	re-search-forward	Search for a regular expression forward.
C-M-r Enter Edit → Search → Regexp Backwards	re-search-backward	Search for a regular expression backward.
C-M-s Edit → Search → Incremental Search → Forward Regexp	isearch-forward-regexp	Search incrementally forward for a regular expression.
C-M-r Edit → Search → Incremental Search → Backward Regexp	isearch-backward-regexp	Search incrementally backward for a regular expression.
C-M-% Edit → Replace → Replace Regexp	query-replace-regexp	Query-replace a regular expression.
(none)	replace-regexp	Globally replace a regular expression unconditionally (use with caution).