std::basic_string<CharT,Traits,Allocator>::rfind

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

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

Parameters

Return value

Position of the first character of the found substring or npos

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

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

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

Exceptions

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

Example

#include <iomanip>
#include <iostream>
#include <string>
 
void print(std::string::size_type n,
           std::string::size_type len,
           std::string const &s)
{
    if (n == std::string::npos)
        std::cout << "not found\n";
    else
        std::cout << "found: " << std::quoted(s.substr(n, len)) << " 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, 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);
}

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

Defect reports

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

See also