Metacharacters, Listed by Linux Program

Some metacharacters are valid for one program but not for another. Those that are available to a given program are marked by a bullet () in the following table. Notes are provided after the table, and full descriptions of metacharacters are in the following section.

Symbol	ed	vi	sed	awk	grep	egrep	Action
.							Match any character (can match newline in gawk).
*							Match zero or more preceding.
^							Match beginning of line or string.
$							Match end of line or string.
\							Escape character following.
[]							Match one from a list or range.
\(\)				Store pattern for later replay.
\n				Reuse matched text stored in nth \( \).
{}		Match a range of instances.
\{\}					Match a range of instances.
\<\>		Match word's beginning or end.
+				Match one or more preceding.
?				Match zero or one preceding.
|			Separate choices to match.
()			Group expressions to match.

On some Linux systems, grep is a link to egrep, so whenever you run grep you actually get egrep behavior.

In ed, vi, and sed, when you perform a search-and-replace (substitute) operation, the metacharacters in this table apply to the pattern you are searching for but not to the string replacing it.

In awk, {} is specified in the POSIX standard and is supported by gawk if you run it with the -Wre-interval option.

In ed, vi, and sed, the following additional metacharacters are valid only in a replacement pattern:

Symbol	ex	sed	ed	Action
\				Escape character following.
\n				Reuse matched text stored in nth \( \).
&			Reuse previous search pattern.
~		Reuse previous replacement pattern.
\e		Turn off previous L or U.
\E		Turn off previous /L or /U.
\l		Change single following character to lowercase.
\L		Change following characters to lowercase until /E encountered.
\u		Change single following character to uppercase.
\U		Change following characters to uppercase until E encountered.