std::strcspn (3) - Linux Manuals
Defined in header <cstring>
size_t strcspn( const char *dest, const char *src );
Returns the length of the maximum initial segment of the byte string pointed to by dest, that consists of only the characters not found in byte string pointed to by src.
The function name stands for "complementary span"
dest - pointer to the null-terminated byte string to be analyzed
src - pointer to the null-terminated byte string that contains the characters to search for
The length of the maximum initial segment that contains only characters not found in the byte string pointed to by src
// Run this code
strspn of only the characters found in another byte string
wcscspn of only the wide not found in another wide string
find_first_of (public member function of std::basic_string<CharT,Traits,Allocator>)