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# std::basic_string::find_first_of

From cppreference.com
< cpp‎ | string‎ | basic string

size_type find_first_of( const basic_string& str, size_type pos = 0 ) const; | (1) |
size_type find_first_of( const CharT* s, size_type pos, size_type count ) const; | (2) |
size_type find_first_of( const CharT* s, size_type pos = 0 ) const; | (3) |
size_type find_first_of( CharT ch, size_type pos = 0 ) const; | (4) |
size_type find_first_of( std::basic_string_view<CharT, Traits> sv, size_type pos = 0 ) const | (5) | (since C++17)

Finds the first character equal to one of the characters in the given character sequence. The search considers only the interval [`pos`, size()). If the character is not present in the interval, npos will be returned.

1) Finds the first character equal to one of the characters in `str` as if by find_first_of(std::basic_string_view<CharT, Traits>(str), pos) (since C++17)
2) Finds the first character equal to one of the characters in the first `count` characters of the character string pointed to by `s`. `s` can include null characters. Equivalent to find_first_of(basic_string(s, count), pos) (until C++17)find_first_of(std::basic_string_view<CharT, Traits>(s, count), pos) (since C++17)
3) Finds the first character equal to one of the characters in character string pointed to by `s`. The length of the string is determined by the first null character. Equivalent to find_first_of(basic_string(s), pos) (until C++17)find_first_of(std::basic_string_view<CharT,Traits>(s), pos) (since C++17)
4) Finds the first character equal to `ch`.
5) Finds the first character equal to one of the characters in `sv`

### [edit] Parameters

str | - | string identifying characters to search for
pos | - | position at which to begin searching
count | - | length of character string identifying characters to search for
s | - | pointer to a character string identifying characters to search for
ch | - | character to search for
sv | - | std::basic_string_view to search for

### [edit] Return value

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

### [edit] Exceptions

1-4) (none) | (until C++11)
1,4) `noexcept` specification: noexcept 2,3) (none) | (since C++11) (until C++14)
1) `noexcept` specification: noexcept 2-4) (none) | (since C++14)
5) `noexcept` specification: noexcept | (since C++17)

### [edit] Notes

traits::eq() is used to perform the comparison.

### [edit] Example

Run this code

    #include <iostream>
    #include <string>

    int main()
    {
        // the test string
        std::string str = std::string("Hello World!");

        // strings and chars to search for
        std::string search_str = std::string("o");
        const char* search_cstr = "Good Bye!";

        std::cout << str.find_first_of(search_str) << '\n';
        std::cout << str.find_first_of(search_str, 5) << '\n';
        std::cout << str.find_first_of(search_cstr) << '\n';
        std::cout << str.find_first_of(search_cstr, 0, 4) << '\n';
        // 'x' is not in "Hello World', thus it will return std::string::npos
        std::cout << str.find_first_of('x') << '\n';
    }

Possible output:

    4
    7
    1
    4
    18446744073709551615

### [edit] See also

find | find characters in the string (public member function) [edit]
rfind | find the last occurrence of a substring (public member function) [edit]
find_first_not_of | find first absence of characters (public member function) [edit]
find_last_of | find last occurrence of characters (public member function) [edit]
find_last_not_of | find last absence of characters (public member function) [edit]
strspn | returns the length of the maximum initial segment that consists of only the characters found in another byte string (function) [edit]

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