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std::string rfind() method

// (1) Const version only
constexpr size_type rfind( const basic_string& str, size_type pos = 0 ) const noexcept;

// (2) Const version only
constexpr size_type rfind( const CharT* s, size_type pos, size_type count ) const;

// (3) Const version only
constexpr size_type rfind( const CharT* s, size_type pos = 0 ) const;

// (4) Const version only
constexpr size_type rfind( CharT ch, size_type pos = 0 ) const noexcept;

// (5) Const version only
template < class StringViewLike >
constexpr size_type rfind( const StringViewLike& t, size_type pos = 0 ) const noexcept(/* see below */);

Finds the last substring equal to the given character sequence.
Search begins at pos, i.e. the found substring must not begin in a position following pos.

  • (1) Finds the last substring equal to str.

  • (2) Finds the last substring equal to the range [ s, s + count ).
    This range may contain null characters.

  • (3) Finds the last substring equal to the character string pointed to by s.
    The length of the string is determined by the last null character using Traits::length(s).

  • (4) Finds the last character ch.

  • (5) Implicitly converts t to a string view sv as if by std::basic_string_view<CharT, Traits> sv = t;, then finds the last substring equal to sv.

    Overload Resolution

    This overload participates in overload resolution only if std::is_convertible_v<const StringViewLike&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false.

note

If npos or any value not smaller than size() - 1 is passed as pos, whole string will be searched.

Parameters​

  • str - string to search for
  • pos - position at which to start the search
  • count - length of substring to search for
  • s - pointer to a character string to search for
  • ch - character to search for
  • t - object (convertible to std::basic_string_view) to search for

Return value​

Position of the first character of the found substring or npos if no such substring is found.

note

That this is an offset from the start of the string, not the end.

If searching for an empty string (str.size(), count, or Traits::length(s) is zero) returns pos (the empty string is found immediately) unless pos > size() (including the case where pos == npos), in which case returns size().

Otherwise, if size() is zero, npos is always returned.

Complexity​

important

This section requires improvement. You can help by editing this doc page.

Exceptions​

  • (1-4) (none)
  • (5) noexcept specification: 
    noexcept(std::is_nothrow_convertible_v<const T&, std::basic_string_view<CharT, Traits>>)

Notes​

Traits::eq() is used for comparison. By default Traits is std::char_traits<CharT>.

Example​

#include <string>
#include <iostream>
 
void print(std::string::size_type n, std::string const &s)
{
    if (n == std::string::npos) {
        std::cout << "not found\n";
    } else {
        std::cout << "found: \"" << s.substr(n) << "\" at " << n << '\n';
    }
}
 
int main()
{
    std::string::size_type n;
    std::string const s = "This is a string";
 
    // search backwards from end of string
    n = s.rfind("is");
    print(n, s);
    // search backwards from position 4
    n = s.rfind("is", 4);
    print(n, s);
    // find a single character
    n = s.rfind('s');
    print(n, s);
    // find a single character
    n = s.rfind('q');
    print(n, s);
}
Output
found: "is a string" at 5
found: "is is a string" at 2
found: "string" at 10
not found
This article originates from this CppReference page. It was likely altered for improvements or editors' preference. Click "Edit this page" to see all changes made to this document.
Hover to see the original license.

std::string rfind() method

// (1) Const version only
constexpr size_type rfind( const basic_string& str, size_type pos = 0 ) const noexcept;

// (2) Const version only
constexpr size_type rfind( const CharT* s, size_type pos, size_type count ) const;

// (3) Const version only
constexpr size_type rfind( const CharT* s, size_type pos = 0 ) const;

// (4) Const version only
constexpr size_type rfind( CharT ch, size_type pos = 0 ) const noexcept;

// (5) Const version only
template < class StringViewLike >
constexpr size_type rfind( const StringViewLike& t, size_type pos = 0 ) const noexcept(/* see below */);

Finds the last substring equal to the given character sequence.
Search begins at pos, i.e. the found substring must not begin in a position following pos.

  • (1) Finds the last substring equal to str.

  • (2) Finds the last substring equal to the range [ s, s + count ).
    This range may contain null characters.

  • (3) Finds the last substring equal to the character string pointed to by s.
    The length of the string is determined by the last null character using Traits::length(s).

  • (4) Finds the last character ch.

  • (5) Implicitly converts t to a string view sv as if by std::basic_string_view<CharT, Traits> sv = t;, then finds the last substring equal to sv.

    Overload Resolution

    This overload participates in overload resolution only if std::is_convertible_v<const StringViewLike&, std::basic_string_view<CharT, Traits>> is true and std::is_convertible_v<const StringViewLike&, const CharT*> is false.

note

If npos or any value not smaller than size() - 1 is passed as pos, whole string will be searched.

Parameters​

  • str - string to search for
  • pos - position at which to start the search
  • count - length of substring to search for
  • s - pointer to a character string to search for
  • ch - character to search for
  • t - object (convertible to std::basic_string_view) to search for

Return value​

Position of the first character of the found substring or npos if no such substring is found.

note

That this is an offset from the start of the string, not the end.

If searching for an empty string (str.size(), count, or Traits::length(s) is zero) returns pos (the empty string is found immediately) unless pos > size() (including the case where pos == npos), in which case returns size().

Otherwise, if size() is zero, npos is always returned.

Complexity​

important

This section requires improvement. You can help by editing this doc page.

Exceptions​

  • (1-4) (none)
  • (5) noexcept specification: 
    noexcept(std::is_nothrow_convertible_v<const T&, std::basic_string_view<CharT, Traits>>)

Notes​

Traits::eq() is used for comparison. By default Traits is std::char_traits<CharT>.

Example​

#include <string>
#include <iostream>
 
void print(std::string::size_type n, std::string const &s)
{
    if (n == std::string::npos) {
        std::cout << "not found\n";
    } else {
        std::cout << "found: \"" << s.substr(n) << "\" at " << n << '\n';
    }
}
 
int main()
{
    std::string::size_type n;
    std::string const s = "This is a string";
 
    // search backwards from end of string
    n = s.rfind("is");
    print(n, s);
    // search backwards from position 4
    n = s.rfind("is", 4);
    print(n, s);
    // find a single character
    n = s.rfind('s');
    print(n, s);
    // find a single character
    n = s.rfind('q');
    print(n, s);
}
Output
found: "is a string" at 5
found: "is is a string" at 2
found: "string" at 10
not found
This article originates from this CppReference page. It was likely altered for improvements or editors' preference. Click "Edit this page" to see all changes made to this document.
Hover to see the original license.