说明：  strtok(char s[], const char *delim) 用来将字符串分割成一个个片段。参数s指向欲分割的字符串，参数delim则为分割字符串中包含的所有字符。当strtok()在参数s的字符串中发现参数delim中包涵的分割字符时,则会将该字符改为\0 字符。在第一次调用时，strtok()必需给予参数s字符串，往后的调用则将参数s设置成NULL。每次调用成功则返回指向被分割出片段的指针。
(strtok- break down a string into tokens (ANSI) A sequence of calls to this routine breaks the string <string> into a sequence of tokens, each of which is delimited by a character from the string <separator>. The first call in the sequence has <string> as its first argument, and is followed by calls with a null pointer as their first argument. The separator string may be different from call to call. The first call in the sequence searches <string> for the first character that is not contained in the current separator string. If the character is not found, there are no tokens in <string> and strtok() returns a null pointer. If the character is found, it is the start of the first token. strtok() then searches from there for a character that is contained in the current separator string. If the character is not found, the current token expands to the end of the string pointed to by <string>, and subsequent searches for a token wil)