std::strcspn (3) - Linux Manuals

std::strcspn: std::strcspn

NAME

std::strcspn - std::strcspn

Synopsis

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"

Parameters

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

Return value

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

Example

// Run this code

  #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';
  }

Output:

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