---
name: "std::match_results"
section: "3"
platform: "linux"
package: "gcc"
version: "16.2.1+r23+gd564253eb6c8-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/std::match_results"
---

# std::match\_results(3)

The results of a match or search operation.

## NAME

std::match\_results\< \_Bi\_iter, \_Alloc \> - The results of a match or search operation.

## SYNOPSIS

\#include \<regex\>

Inherits **std::vector\< \_Tp, \_Alloc \>**.

### Public Types

**28.10 Public Types**\

typedef **sub\_match**\< \_Bi\_iter \> **value\_type**\
 typedef const value\_type & **const\_reference**\
 typedef value\_type & **reference**\
 typedef \_Base\_type::const\_iterator **const\_iterator**\
 typedef const\_iterator **iterator**\
 typedef \_\_iter\_traits::difference\_type **difference\_type**\
 typedef **allocator\_traits**\< \_Alloc \>::size\_type **size\_type**\
 typedef \_Alloc **allocator\_type**\
 typedef \_\_iter\_traits::value\_type **char\_type**\
 typedef **std::basic\_string**\< char\_type \> **string\_type**\

### Public Member Functions

template\<typename \_Out\_iter\> \_Out\_iter **format** (\_Out\_iter \_\_out, const **match\_results**\< \_Bi\_iter, \_Alloc \>::char\_type \*\_\_fmt\_first, const **match\_results**\< \_Bi\_iter, \_Alloc \>::char\_type \*\_\_fmt\_last, **match\_flag\_type** \_\_flags) const\
 bool **ready** () const noexcept\
 Indicates if the match\_results is ready.

**28.10.1 Construction, Copying, and Destruction**\

**match\_results** ()\
 Constructs a default match\_results container.  **match\_results** (const \_Alloc &\_\_a) noexcept\
 Constructs a default match\_results container.  **match\_results** (const match\_results &)=default\
 Copy constructs a match\_results.  **match\_results** (match\_results &&) noexcept=default\
 Move constructs a match\_results.  **match\_results** & **operator=** (const **match\_results** &)=default\
 Assigns rhs to \*this.  **match\_results** & **operator=** (**match\_results** &&)=default\
 Move-assigns rhs to \*this.  **~match\_results** ()=default\
 Destroys a match\_results object.  **match\_results** (const match\_results &\_\_m, const \_Alloc &\_\_a)\
 Constructs a default match\_results container.  **match\_results** (match\_results &&\_\_m, const \_Alloc &\_\_a) noexcept(noexcept(\_Base\_type(**std::move**(\_\_m), \_\_a)))\
 Constructs a default match\_results container.

**28.10.2 Size**\

size\_type **size** () const noexcept\
 Gets the number of matches and submatches.  size\_type **max\_size** () const noexcept\
 Gets the number of matches and submatches.  bool **empty** () const noexcept\
 Indicates if the match\_results contains no results.

**28.10.4 Element Access**\

difference\_type **length** (size\_type \_\_sub=0) const\
 Gets the length of the indicated submatch.  difference\_type **position** (size\_type \_\_sub=0) const\
 Gets the offset of the beginning of the indicated submatch.  string\_type **str** (size\_type \_\_sub=0) const\
 Gets the match or submatch converted to a string type.  const\_reference **operator\[\]** (size\_type \_\_sub) const\
 Gets a sub\_match reference for the match or submatch.  const\_reference **prefix** () const\
 Gets a sub\_match representing the match prefix.  const\_reference **suffix** () const\
 Gets a sub\_match representing the match suffix.  const\_iterator **begin** () const noexcept\
 Gets an iterator to the start of the sub\_match collection.  const\_iterator **cbegin** () const noexcept\
 Gets an iterator to the start of the sub\_match collection.  const\_iterator **end** () const noexcept\
 Gets an iterator to one-past-the-end of the collection.  const\_iterator **cend** () const noexcept\
 Gets an iterator to one-past-the-end of the collection.

**28.10.5 Formatting**\
 These functions perform formatted substitution of the matched character sequences into their target. The format specifiers and escape sequences accepted by these functions are determined by their flags parameter as documented above.

template\<typename \_Out\_iter\> \_Out\_iter **format** (\_Out\_iter \_\_out, const char\_type \*\_\_fmt\_first, const char\_type \*\_\_fmt\_last, **match\_flag\_type** \_\_flags=**regex\_constants::format\_default**) const\
 template\<typename \_Out\_iter, typename \_St, typename \_Sa\> \_Out\_iter **format** (\_Out\_iter \_\_out, const **basic\_string**\< char\_type, \_St, \_Sa \> &\_\_fmt, **match\_flag\_type** \_\_flags=**regex\_constants::format\_default**) const\
 template\<typename \_St, typename \_Sa\> **basic\_string**\< char\_type, \_St, \_Sa \> **format** (const **basic\_string**\< char\_type, \_St, \_Sa \> &\_\_fmt, **match\_flag\_type** \_\_flags=**regex\_constants::format\_default**) const\
 string\_type **format** (const char\_type \*\_\_fmt, **match\_flag\_type** \_\_flags=**regex\_constants::format\_default**) const\

**28.10.6 Allocator**\

allocator\_type **get\_allocator** () const noexcept\
 Gets a copy of the allocator.

**28.10.7 Swap**\

void **swap** (**match\_results** &\_\_that) noexcept\
 Swaps the contents of two match\_results.

### Private Member Functions

constexpr iterator **begin** () noexcept\
 constexpr iterator **end** () noexcept\
 constexpr const\_reference **operator\[\]** (size\_type \_\_n) const noexcept\
 Subscript access to the data contained in the vector.  constexpr reference **operator\[\]** (size\_type \_\_n) noexcept\
 Subscript access to the data contained in the vector.  constexpr void **swap** (**vector** &\_\_x) noexcept\
 Swaps data with another vector.

### Friends

template\<typename, typename, typename\> class **regex\_iterator**\

### Related Symbols

(Note that these are not member symbols.)  template\<typename \_Bi\_iter, typename \_Alloc\> bool **operator==** (const **match\_results**\< \_Bi\_iter, \_Alloc \> &\_\_m1, const **match\_results**\< \_Bi\_iter, \_Alloc \> &\_\_m2)\
 Compares two match\_results for equality.  template\<typename \_Bi\_iter, typename \_Alloc\> void **swap** (**match\_results**\< \_Bi\_iter, \_Alloc \> &\_\_lhs, **match\_results**\< \_Bi\_iter, \_Alloc \> &\_\_rhs) noexcept\
 Swaps two match results.

## Detailed Description

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\>

class std::match\_results\< \_Bi\_iter, \_Alloc \>"The results of a match or search operation.

A collection of character sequences representing the result of a regular expression match. Storage for the collection is allocated and freed as necessary by the member functions of class template match\_results.

This class satisfies the Sequence requirements, with the exception that only the operations defined for a const-qualified Sequence are supported.

The sub\_match object stored at index 0 represents sub-expression 0, i.e. the whole match. In this case the sub\_match member matched is always true. The sub\_match object stored at index n denotes what matched the marked sub-expression n within the matched expression. If the sub-expression n participated in a regular expression match then the sub\_match member matched evaluates to true, and members first and second denote the range of characters \[first, second) which formed that match. Otherwise matched is false, and members first and second point to the end of the sequence that was searched.

**Since**

C++11

## Constructor & Destructor Documentation

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> std::match\_results\< \_Bi\_iter, \_Alloc \>::match\_results () \[inline\]

Constructs a default match\_results container.

**Postcondition**

size() returns 0 and str() returns an empty string.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> std::match\_results\< \_Bi\_iter, \_Alloc \>::match\_results (const \_Alloc & \_\_a) \[inline\], \[explicit\], \[noexcept\]

Constructs a default match\_results container.

**Postcondition**

size() returns 0 and str() returns an empty string.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> std::match\_results\< \_Bi\_iter, \_Alloc \>::match\_results (const match\_results\< \_Bi\_iter, \_Alloc \> & ) \[default\]

Copy constructs a match\_results.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> std::match\_results\< \_Bi\_iter, \_Alloc \>::match\_results (match\_results\< \_Bi\_iter, \_Alloc \> && ) \[default\], \[noexcept\]

Move constructs a match\_results.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> std::match\_results\< \_Bi\_iter, \_Alloc \>::~match\_results () \[default\]

Destroys a match\_results object.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> std::match\_results\< \_Bi\_iter, \_Alloc \>::match\_results (const match\_results\< \_Bi\_iter, \_Alloc \> & \_\_m, const \_Alloc & \_\_a) \[inline\]

Constructs a default match\_results container.

**Postcondition**

size() returns 0 and str() returns an empty string.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> std::match\_results\< \_Bi\_iter, \_Alloc \>::match\_results (match\_results\< \_Bi\_iter, \_Alloc \> && \_\_m, const \_Alloc & \_\_a) \[inline\], \[noexcept\]

Constructs a default match\_results container.

**Postcondition**

size() returns 0 and str() returns an empty string.

## Member Function Documentation

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> const\_iterator std::match\_results\< \_Bi\_iter, \_Alloc \>::begin () const \[inline\], \[noexcept\]

Gets an iterator to the start of the sub\_match collection.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::cbegin()**, and **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator==()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> const\_iterator std::match\_results\< \_Bi\_iter, \_Alloc \>::cbegin () const \[inline\], \[noexcept\]

Gets an iterator to the start of the sub\_match collection.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> const\_iterator std::match\_results\< \_Bi\_iter, \_Alloc \>::cend () const \[inline\], \[noexcept\]

Gets an iterator to one-past-the-end of the collection.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> bool std::match\_results\< \_Bi\_iter, \_Alloc \>::empty () const \[inline\], \[nodiscard\], \[noexcept\]

Indicates if the match\_results contains no results.

**Return values**

*true* The match\_results object is empty. \
 *false* The match\_results object is not empty.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator==()**, **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::prefix()**, and **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::suffix()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> const\_iterator std::match\_results\< \_Bi\_iter, \_Alloc \>::end () const \[inline\], \[noexcept\]

Gets an iterator to one-past-the-end of the collection.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::cend()**, and **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator==()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> template\<typename \_Out\_iter, typename \_St, typename \_Sa\> \_Out\_iter std::match\_results\< \_Bi\_iter, \_Alloc \>::format (\_Out\_iter \_\_out, const basic\_string\< char\_type, \_St, \_Sa \> & \_\_fmt, match\_flag\_type \_\_flags = regex\_constants::format\_default) const \[inline\]

**Precondition**

ready() == true

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> template\<typename \_Out\_iter\> \_Out\_iter std::match\_results\< \_Bi\_iter, \_Alloc \>::format (\_Out\_iter \_\_out, const char\_type \* \_\_fmt\_first, const char\_type \* \_\_fmt\_last, match\_flag\_type \_\_flags = regex\_constants::format\_default) const

**Precondition**

ready() == true

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::format()**, **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::format()**, and **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::format()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> template\<typename \_St, typename \_Sa\> basic\_string\< char\_type, \_St, \_Sa \> std::match\_results\< \_Bi\_iter, \_Alloc \>::format (const basic\_string\< char\_type, \_St, \_Sa \> & \_\_fmt, match\_flag\_type \_\_flags = regex\_constants::format\_default) const \[inline\]

**Precondition**

ready() == true

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> string\_type std::match\_results\< \_Bi\_iter, \_Alloc \>::format (const char\_type \* \_\_fmt, match\_flag\_type \_\_flags = regex\_constants::format\_default) const \[inline\]

**Precondition**

ready() == true

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> allocator\_type std::match\_results\< \_Bi\_iter, \_Alloc \>::get\_allocator () const \[inline\], \[noexcept\]

Gets a copy of the allocator.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> difference\_type std::match\_results\< \_Bi\_iter, \_Alloc \>::length (size\_type \_\_sub = 0) const \[inline\]

Gets the length of the indicated submatch.

**Parameters**

*\_\_sub* indicates the submatch.

**Precondition**

ready() == true

This function returns the length of the indicated submatch, or the length of the entire match if \_\_sub is zero (the default).

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> size\_type std::match\_results\< \_Bi\_iter, \_Alloc \>::max\_size () const \[inline\], \[noexcept\]

Gets the number of matches and submatches. The number of matches for a given regular expression will be either 0 if there was no match or mark\_count() + 1 if a match was successful. Some matches may be empty.

**Returns**

the number of matches found.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> match\_results & std::match\_results\< \_Bi\_iter, \_Alloc \>::operator= (const match\_results\< \_Bi\_iter, \_Alloc \> & ) \[default\]

Assigns rhs to \*this.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> match\_results & std::match\_results\< \_Bi\_iter, \_Alloc \>::operator= (match\_results\< \_Bi\_iter, \_Alloc \> && ) \[default\]

Move-assigns rhs to \*this.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> const\_reference std::match\_results\< \_Bi\_iter, \_Alloc \>::operator\[\] (size\_type \_\_sub) const \[inline\]

Gets a sub\_match reference for the match or submatch.

**Parameters**

*\_\_sub* indicates the submatch.

**Precondition**

ready() == true

This function gets a reference to the indicated submatch, or the entire match if \_\_sub is zero.

If \_\_sub \>= size() then this function returns a sub\_match with a special value indicating no submatch.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> difference\_type std::match\_results\< \_Bi\_iter, \_Alloc \>::position (size\_type \_\_sub = 0) const \[inline\]

Gets the offset of the beginning of the indicated submatch.

**Parameters**

*\_\_sub* indicates the submatch.

**Precondition**

ready() == true

This function returns the offset from the beginning of the target sequence to the beginning of the submatch, unless the value of \_\_sub is zero (the default), in which case this function returns the offset from the beginning of the target sequence to the beginning of the match.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> const\_reference std::match\_results\< \_Bi\_iter, \_Alloc \>::prefix () const \[inline\]

Gets a sub\_match representing the match prefix.

**Precondition**

ready() == true

This function gets a reference to a sub\_match object representing the part of the target range between the start of the target range and the start of the match.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator==()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> bool std::match\_results\< \_Bi\_iter, \_Alloc \>::ready () const \[inline\], \[noexcept\]

Indicates if the match\_results is ready.

**Return values**

*true* The object has a fully-established result state. \
 *false* The object is not ready.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator==()**, **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator\[\]()**, **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::prefix()**, and **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::suffix()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> size\_type std::match\_results\< \_Bi\_iter, \_Alloc \>::size () const \[inline\], \[noexcept\]

Gets the number of matches and submatches. The number of matches for a given regular expression will be either 0 if there was no match or mark\_count() + 1 if a match was successful. Some matches may be empty.

**Returns**

the number of matches found.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator==()**, and **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator\[\]()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> string\_type std::match\_results\< \_Bi\_iter, \_Alloc \>::str (size\_type \_\_sub = 0) const \[inline\]

Gets the match or submatch converted to a string type.

**Parameters**

*\_\_sub* indicates the submatch.

**Precondition**

ready() == true

This function gets the submatch (or match, if \_\_sub is zero) extracted from the target range and converted to the associated string type.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> const\_reference std::match\_results\< \_Bi\_iter, \_Alloc \>::suffix () const \[inline\]

Gets a sub\_match representing the match suffix.

**Precondition**

ready() == true

This function gets a reference to a sub\_match object representing the part of the target range between the end of the match and the end of the target range.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::operator==()**.

### template\<typename \_Bi\_iter, typename \_Alloc = allocator\<sub\_match\<\_Bi\_iter\> \>\> void std::match\_results\< \_Bi\_iter, \_Alloc \>::swap (match\_results\< \_Bi\_iter, \_Alloc \> & \_\_that) \[inline\], \[noexcept\]

Swaps the contents of two match\_results.

Referenced by **std::match\_results\< \_BidirectionalIterator, polymorphic\_allocator\< sub\_match\< \_BidirectionalIterator \> \> \>\< const char \* \>::swap()**.

## Author

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