Функция strtok, нужны комментарии к коду

STRTOK(3)                                        Linux Programmer's Manual                                       STRTOK(3)
 
NAME
       strtok, strtok_r - extract tokens from strings
 
SYNOPSIS
       #include <string.h>
 
       char *strtok(char *str, const char *delim);
 
       char *strtok_r(char *str, const char *delim, char **saveptr);
 
   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
 
       strtok_r(): _SVID_SOURCE || _BSD_SOURCE || _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
 
DESCRIPTION
       The  strtok()  function  parses a string into a sequence of tokens.  On the first call to strtok() the string to be
       parsed should be specified in str.  In each subsequent call that should parse the same string, str should be NULL.
 
       The delim argument specifies a set of characters that delimit the tokens in the  parsed  string.   The  caller  may
       specify different strings in delim in successive calls that parse the same string.
 
       Each  call  to  strtok() returns a pointer to a null-terminated string containing the next token.  This string does
       not include the delimiting character.  If no more tokens are found, strtok() returns NULL.
 
       A sequence of two or more contiguous delimiter characters in the parsed string is considered to be a single  delim‐
       iter.  Delimiter characters at the start or end of the string are ignored.  Put another way: the tokens returned by
       strtok() are always nonempty strings.
 
       The strtok_r() function is a reentrant version strtok().  The saveptr argument is a pointer to a  char  *  variable
       that  is  used  internally  by strtok_r() in order to maintain context between successive calls that parse the same
       string.
       On the first call to strtok_r(), str should point to the string to be parsed, and the value of saveptr is  ignored.
       In subsequent calls, str should be NULL, and saveptr should be unchanged since the previous call.
 
       Different  strings may be parsed concurrently using sequences of calls to strtok_r() that specify different saveptr
       arguments.
 
RETURN VALUE
       The strtok() and strtok_r() functions return a pointer to the next token, or NULL if there are no more tokens.