#include <string.h>
#include <stdio.h>

/* Output is

Found a tab character in w_space
Found a line termination (ASCII 0) character in w_space

   ...i.e.,  the '\0' character is found in w_space,  at its end. */

int main( void)
{
   const char *w_space = " \t\n\r";

   if( strchr( w_space, '\t'))
      printf( "Found a tab character in w_space\n");
   if( strchr( w_space, 'z'))
      printf( "Found a z character in w_space\n");
   if( strchr( w_space, '\0'))
      printf( "Found a line termination (ASCII 0) character in w_space\n");
   return( 0);
}