Replacement Reference

Replacement Strings Reference: Matched Text and Backreferences

Feature	Syntax	Description	Example	JGsoft	.NET	Java	Perl	PCRE2	PHP	Delphi	R	JavaScript	VBScript	XRegExp	Python	Ruby	std::regex	Boost	Tcl ARE	Oracle	XPath
Ampersand	`\&`	Insert a literal ampersand.	Replacing with `\&` yields `&`	no	no	YES	YES	extended	no	no	YES	no	no	no	no	no	sed	YES	YES	no	error
Whole match	`\&`	Insert the whole regex match.	Replacing `\d+` with `[\&]` in `1a2b` yields `[1]a[2]b`	YES	no	no	no	no	no	YES	no	no	no	no	no	YES	no	no	no	no	error
Whole match	`$&`	Insert the whole regex match.	Replacing `\d+` with `[$&]` in `1a2b` yields `[1]a[2]b`	YES	YES	error	YES	error	no	YES	no	YES	YES	YES	no	no	default	all default	no	no	error
Whole match	`&`	Insert the whole regex match.	Replacing `\d+` with `[&]` in `1a2b` yields `[1]a[2]b`	no	no	no	no	no	no	no	no	no	no	no	no	no	sed	sed	YES	no	no
Whole match	`\0`	Insert the whole regex match.	Replacing `\d+` with `[\0]` in `1a2b` yields `[1]a[2]b`	YES	no	no	no	no	YES	YES	no	no	no	no	no	YES	sed	sed	YES	no	error
Whole match	`$0`	Insert the whole regex match.	Replacing `\d+` with `[$0]` in `1a2b` yields `[1]a[2]b`	YES	YES	YES	error	YES	YES	YES	no	no	no	YES	no	no	default VC’08–VC’13	all default	no	no	YES
Whole match	`\g<0>`	Insert the whole regex match.	Replacing `\d+` with `[\g<0>]` in `1a2b` yields `[1]a[2]b`	YES	no	no	no	no	no	no	no	no	no	no	YES	no	no	no	no	no	error
Whole match	`$MATCH` and `${^MATCH}`	Insert the whole regex match.	Replacing `\d+` with `[$MATCH]` in `1a2b` yields `[1]a[2]b`	no	no	error	error	error	no	no	no	no	no	error	no	no	no	all default 1.42–1.85	no	no	error
Backreference	`\1` through `\9`	Insert the text matched by one of the first 9 capturing groups.	Replacing `(a)(b)(c)` with `\3\3\1` in `abc` yields `cca`	YES	no	no	YES	no	YES	YES	YES	no	no	no	YES	YES	sed	YES	YES	YES	error
Backreference	`\10` through `\99`	Insert the text matched by capturing groups 10 through 99.		YES	no	no	no	no	YES	YES	no	no	no	no	YES	no	no	no	no	no	no
Backreference and literal	`\10` through `\99`	When there are fewer capturing groups than the 2-digit number, treat this as a single-digit backreference followed by a literal number instead of as an invalid backreference.	Replacing `(a)(b)(c)` with `\39\38\17` in `abc` yields `c9c8a7`	YES	n/a	n/a	n/a	n/a	no	YES	n/a	n/a	n/a	n/a	no	n/a	n/a	n/a	n/a	n/a	n/a
Backreference	`$1` through `$9`	Insert the text matched by one of the first 9 capturing groups.	Replacing `(a)(b)(c)` with `$3$3$1` in `abc` yields `cca`	YES	YES	YES	YES	YES	YES	YES	no	YES	YES	YES	no	no	default	all default	no	no	YES
Backreference	`$10` through `$99`	Insert the text matched by capturing groups 10 through 99.		YES	YES	YES	YES	YES	YES	YES	no	YES	YES	YES	no	no	default	all default	no	no	YES
Backreference and literal	`$10` through `$99`	When there are fewer capturing groups than the 2-digit number, treat this as a single-digit backreference followed by a literal number instead of as an invalid backreference.	Replacing `(a)(b)(c)` with `$39$38$17` in `abc` yields `c9c8a7`	YES	ECMA	YES	no	no	no	YES	n/a	YES	YES	no	n/a	n/a	no	no	n/a	n/a	YES
Backreference	`${1}` through `${99}`	Insert the text matched by capturing groups 1 through 99.	Replacing `(a)(b)(c)` with `${3}${3}${1}` in `abc` yields `cca`	YES	YES	error	YES	YES	YES	YES	no	no	no	YES	no	no	no	all default	no	no	error
Backreference	`\g<1>` through `\g<99>`	Insert the text matched by capturing groups 1 through 99.	Replacing `(a)(b)(c)` with `\g<3>\g<3>\g<1>` in `abc` yields `cca`	YES	no	no	no	no	no	no	no	no	no	no	YES	no	no	no	no	no	error
Named backreference	`${name}`	Insert the text matched by the named capturing group “name”.	Replacing `(?'one'a)(?'two'b)` with `${two}${one}` in `ab` yields `ba`	YES	YES	7	error	YES	no	YES	no	no	no	YES	no	no	no	no	no	no	error
Named backreference	`$+{name}`	Insert the text matched by the named capturing group “name”.	Replacing `(?'one'a)(?'two'b)` with `$+{two}$+{one}` in `ab` yields `ba`	no	no	error	5.10	error	no	no	no	no	no	error	no	no	no	all default 1.42–1.85	no	no	error
Named backreference	`$name`	Insert the text matched by the named capturing group “name”.	Replacing `(?'one'a)(?'two'b)` with `$two$one` in `ab` yields `ba`	no	no	error	error	YES	no	no	no	no	no	error	no	no	no	no	no	no	error
Named backreference	`\g<name>`	Insert the text matched by the named capturing group “name”.	Replacing `(?P<one>a)(?P<two>b)` with `\g<two>\g<one>` in `ab` yields `ba`	YES	no	no	no	no	no	YES	no	no	no	no	YES	no	no	no	no	no	error
Invalid backreference	Any supported backreference syntax	A backreference that indicates a number greater than the highest-numbered group or a name of a group that does not exist is replaced with the empty string.		V1 only	no	error	YES	error	YES	YES	YES	no	no	error	error	YES	default VC’08–VC’22 sed VC’15–VC’22	YES	YES	YES	YES
Invalid backreference	Any supported backreference syntax	A backreference that indicates a number greater than the highest-numbered group or a name of a group that does not exist is treated as literal text that is inserted as such in the replacement.		V2 error	YES	error	no	error	no	no	no	YES	YES	error	error	no	sed VC’08–VC’13 error	no	no	no	no
Backreference to non-participating group	Any supported backreference syntax	A backreference to a non-participating capturing group is replaced with the empty string.		YES	YES	YES	YES	error	YES	YES	YES	YES	YES	YES	3.5	YES	YES	YES	YES	YES	YES
Last backreference	`\+`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[\+]` in `ab` yields `[a]b`	YES	no	no	no	no	no	YES	no	no	no	no	no	YES	no	no	no	no	error
Last backreference	`\+`	Insert the text matched by the highest-numbered capturing group, regardless of whether it participated in the match.	Replacing `(a)(z)?` with `[\+]` in `ab` yields `[]b`	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	no	error
Last backreference	`$+`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[$+]` in `ab` yields `[a]b`	YES	no	error	5.18	error	no	YES	no	no	no	error	no	no	no	no	no	no	error
Last backreference	`$+`	Insert the text matched by the highest-numbered capturing group, regardless of whether it participated in the match.	Replacing `(a)(z)?` with `[$+]` in `ab` yields `[]b`	no	YES	error	5.8–5.16	error	no	no	no	no	YES	error	no	no	no	all default 1.42–1.85	no	no	error
Last backreference	`$^N`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[$^N]` in `ab` yields `[a]b`	no	no	error	YES	error	no	no	no	no	no	error	no	no	no	all default 1.42–1.85	no	no	error
Last backreference	`$LAST_SUBMATCH_RESULT` and `${^LAST_SUBMATCH_RESULT}`	Insert the text matched by the highest-numbered capturing group that actually participated in the match.	Replacing `(a)(z)?` with `[$LAST_SUBMATCH_RESULT]` in `ab` yields `[a]b`	no	no	error	error	error	no	no	no	no	no	error	no	no	no	all default 1.42–1.85	no	no	error
Last backreference	`$LAST_PAREN_MATCH` and `${^LAST_PAREN_MATCH}`	Insert the text matched by the highest-numbered capturing group, regardless of whether it participated in the match.	Replacing `(a)(z)?` with `[$LAST_PAREN_MATCH]` in `ab` yields `[]b`	no	no	error	error	error	no	no	no	no	no	error	no	no	no	all default 1.42–1.85	no	no	error
Feature	Syntax	Description	Example	JGsoft	.NET	Java	Perl	PCRE2	PHP	Delphi	R	JavaScript	VBScript	XRegExp	Python	Ruby	std::regex	Boost	Tcl ARE	Oracle	XPath