std::regex_replace

Parameters

s

A string with the target sequence (the subject).

rgx

A basic_regex object (the pattern) to match.

fmt

A string with the replacement for each match.
This may include format specifiers and escape sequences that are replaced by the characters they represent. For format_default, the possible specifiers are:

characters	replacement
$n	n-th backreference (i.e., a copy of the n-th matched group specified with parentheses in the regex pattern). n must be an integer value designating a valid backreference, greater than 0, and of two digits at most.
$&	A copy of the entire match
$`	The prefix (i.e., the part of the target sequence that precedes the match).
$´	The suffix (i.e., the part of the target sequence that follows the match).
$$	A single $ character.

flags

Flags used to control how rgx is matched and how fmt is formatted.
One or more of these constants can be combined (using the bitwise OR operator, |) to form a valid bitmask value of type regex_constants::match_flag_type:

flag*	effects	notes
match_default	Default	Default matching behavior. This constant has a value of zero**.
match_not_bol	Not Beginning-Of-Line	The first character is not considered a beginning of line ("^" does not match).
match_not_eol	Not End-Of-Line	The last character is not considered an end of line ("$" does not match).
match_not_bow	Not Beginning-Of-Word	The escape sequence "\b" does not match as a beginning-of-word.
match_not_eow	Not End-Of-Word	The escape sequence "\b" does not match as an end-of-word.
match_any	Any match	Any match is acceptable if more than one match is possible.
match_not_null	Not null	Empty sequences do not match.
match_continuous	Continuous	The expression must match a sub-sequence that begins at the first character. Sub-sequences must begin at the first character to match.
match_prev_avail	Previous Available	One or more characters exist before the first one. (match_not_bol and match_not_bow are ignored)
format_default	Default formatting	Uses the standard formatting rules to replace matches (those used by ECMAScript's replace method). This constant has a value of zero**.
format_sed	sed formatting	Uses the same rules as the sed utility in POSIX to replace matches.
format_no_copy	No copy	The sections in the target sequence that do not match the regular expression are not copied when replacing matches.
format_first_only	First only	Only the first occurrence of a regular expression is replaced.

* These bitmask flag names are available under the std::regex_constants namespace (see regex_constants for more details).
** Constants with a value of zero are ignored if some other flag is set.
match_flag_type is a type available under the std::regex_constants namespace.

out

Output iterator pointing to the first character of a sequence where the resulting sequence is stored.
The function template type can be any type of output iterator to characters.

first, last

Bidirectional iterators to the initial and final positions in the range of characters used as target sequence for the match. The range used is [first,last), which includes all the characters between first and last, including the character pointed by first but not the character pointed by last.
The function template type can be any type of bidirectional iterator to characters.

Return value

Example

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// regex_replace example
#include <iostream>
#include <string>
#include <regex>
#include <iterator>

int main ()
{
  std::string s ("there is a subsequence in the string\n");
  std::regex e ("\\b(sub)([^ ]*)");   // matches words beginning by "sub"

  // using string/c-string (3) version:
  std::cout << std::regex_replace (s,e,"sub-$2");

  // using range/c-string (6) version:
  std::string result;
  std::regex_replace (std::back_inserter(result), s.begin(), s.end(), e, "$2");
  std::cout << result;

  // with flags:
  std::cout << std::regex_replace (s,e,"$1 and $2",std::regex_constants::format_no_copy);
  std::cout << std::endl;

  return 0;
}

there is a sub-sequence in the string
there is a sequence in the string
sub and sequence

See also

regex_match

Match sequence (function template)

regex_search

Search sequence (function template)

regex_iterator

Regex iterator (class template)