std::basic_string<CharT,Traits,Allocator>::rfind - cppreference.com (original) (raw)

Finds the last substring that is equal to the given character sequence. The search begins at pos and proceeds from right to left (thus, the found substring, if any, cannot begin in a position following pos). If npos or any value not smaller than size() - 1 is passed as pos, the whole string will be searched.

1. Finds the last substring equal to str.

2. Finds the last substring equal to the range [s, s + count). This range can include null characters.

If [s, s + count) is not a valid range, the behavior is undefined.

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

If [s, s + Traits::length(s)) is not a valid range, the behavior is undefined.

1. Finds the last character equal to ch.

2. 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 the contents of sv.

In all cases, equality is checked by calling Traits::eq.

[edit] Parameters

[edit] 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 (i.e., str.size(), count, or Traits::length(s) is zero), the empty string is found immediately and rfind returns:

• pos, if pos < size();
• size() otherwise, including the case where pos == npos.

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

[edit] Exceptions

1,4) Throws nothing.

If an exception is thrown for any reason, this function has no effect (strong exception safety guarantee).

[edit] Example

#include #include #include   void print(std:🧵:size_type n, std:🧵:size_type len, std::string const &s) { if (n == std:🧵:npos) std::cout << "not found\n"; else std::cout << "found: " << std::quoted(s.substr(n, len)) << " at " << n << '\n'; }   int main() { std:🧵:size_type n; std::string const s = "This is a string";   // search backwards from end of string n = s.rfind("is"); print(n, 2, s);   // search backwards from position 4 n = s.rfind("is", 4); print(n, 2, s);   // find a single character n = s.rfind('s'); print(n, 1, s);   // find a single character n = s.rfind('q'); print(n, 1, s);   // find the prefix (see also s.starts_with("This")) n = s.rfind("This", 0); print(n, 4, s); }

Output:

found: "is" at 5 found: "is" at 2 found: "s" at 10 not found found: "This" at 0

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[edit] See also