std::strcspn

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"

Parameters

Return value

The length of the maximum initial segment that contains only characters not found in the byte string pointed to by src.

Example

#include <string>
#include <cstring>
#include <iostream>
 
const char* invalid = "*$#";
int main()
{
    std::string s = "abcde312$#@";
 
    size_t valid_len = std::strcspn(s.c_str(), invalid);
    if(valid_len != s.size())
       std::cout << "'" << s << "' contains invalid chars starting at position "
                 << valid_len << '\n';
}

'abcde312$#@' contains invalid chars starting at position 8

See also