Defined in header <string.h> (1) char * strtok ( char * str , const char * delim ) ; (until C99) char * strtok ( char * restrict str , const char * restrict delim ) ; (since C99) char * strtok_s ( char * restrict str , rsize_t * restrict strmax , const char * restrict delim , char * * restrict ptr ) ; (2) (since C11) 1) Finds the next token in a null-terminated byte string pointed to by str . The separator characters are identified by null-terminated byte string pointed to by delim . This function is designed to be called multiples times to obtain successive tokens from the same string. If str ! = NULL , the call is treated as the first call to strtok for this particular string. The function searches for the first character which is not contained in delim . If no such character was found, there are no tokens in str at all, and the function returns a null pointer. If such character was found, ...