Linux in a Nutshell, 6th Edition

Metacharacters, Listed by Program

Some metacharacters are valid for one program but not for another. Those that are available are marked by a bullet (•) in the following table. Items marked with a “P” are specified by POSIX. Full descriptions were provided in the previous section.

Symbol	ed	ex	vi	sed	gawk	grep	egrep	Action
•	•	•	•	•	•	•	•	Match any character.
*	•	•	•	•	•	•	•	Match zero or more preceding characters.
^	•	•	•	•	•	•	•	Match beginning of line/string.
$	•	•	•	•	•	•	•	Match end of line/string.
\	•	•	•	•	•	•	•	Escape following character.
[ ]	•	•	•	•	•	•	•	Match one from a set.
\( \)	•	•	•	•		•		Store pattern for later replay.[a]
\n	•	•	•	•		•		Replay subpattern in match.
{ }					• P		• P	Match a range of instances.
\{ \}	•			•		•		Match a range of instances.
\< \>	•	•	•					Match word’s beginning or end.
+					•		•	Match one or more preceding characters.
?					•		•	Match zero or one preceding characters.
|					•		•	Separate choices to match.
( )					•		•	Group expressions to match.
[a] Stored subpatterns can be “replayed” during matching. See the following table.

Note that in ed, ex, vi, and sed, you specify both a search pattern (on the left) and a replacement pattern (on the right). The metacharacters listed above are meaningful only in a search pattern.

In ed, ex, vi, and sed, the metacharacters in the following table are valid only in a replacement pattern.

Symbol	ex	vi	sed	ed	Action
\	•	•	•	•	Escape following character.
\n	•	•	•	•	Text matching pattern stored in \( \).
&	•	•	•	•	Text matching search pattern.
~	•	•			Reuse previous replacement pattern.
%				•	Reuse previous replacement pattern.
\u \U	•	•