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, ...