strtok.c

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

char *myStrtok(char * str, const char *delim)
{
  static char * s = NULL;
  char * ret = NULL;
  if(str != NULL)
  {
    s = str;
  }
  if(s != NULL && strlen(s))
  {
    const size_t dlen = strlen(delim);
    //Skip consecutive delimiters.
    while(*s && memchr(delim, *s, dlen) != NULL)
    {
      ++s;
    }
    //If the beginning of the token is not at the end of the string...
    if(*s)
    {
      //Set our retval to the first non-delim char.
      ret = s;
      //Search for the next non-delim character, if any.
      while(*s)
      {
        if(memchr(delim, *s, dlen) != NULL)
        {
          break;
        }
        else
        {
          ++s;
        }
      }
      if(*s)
      {
        //Null-terminate the token and march the stored pointer forward.
        s[0] = 0;
        ++s;
      }
    }
  }
  return ret;
}

int main()
{
  char * str = strdup("    This is     a     String, of Things.  !    ");
  const char * tok = myStrtok(str, " ,.!");
  while(tok != NULL)
  {
    printf("'%s'\n", tok);
    tok = myStrtok(NULL, " ,.!");
  }
  free(str);
  return 0;
}