有个弱智的问题想问

如果系统安装了man中的Technical Reference（一般命令帮助是Command Reference），用man 2 strtok命令就可以看。

char *strtok (String1, String2)
char *String1;
const char *String2;

Attention: Do not use the strtok subroutine in a multithreaded environment.

The strtok subroutine breaks the string pointed to by the String1 parameter into a sequence of tokens, each of which is delimited by a byte from the string pointed to by the String2 parameter. The first call in the sequence takes the String1 parameter as its first argument and is followed by calls that take a null pointer as their first argument. The separator string pointed to by the String2 parameter may be different from call to call.

The first call in the sequence searches the String1 parameter for the first byte that is not contained in the current separator string pointed to by the String2 parameter. If no such byte is found, no tokens exist in the string pointed to by the String1 parameter, and a null pointer is returned. If such a byte is found, it is the start of the first token.

The strtok subroutine then searches from the first token for a byte that is contained in the current separator string. If no such byte is found, the current token extends to the end of the string pointed to by the String1 parameter, and subsequent searches for a token return a null pointer. If such a byte is found, the strtok subroutine overwrites it with a null byte, which terminates the current token. The strtok subroutine saves a pointer to the following byte, from which the next search for a token will start. The subroutine returns a pointer to the first byte of the token.

Each subsequent call with a null pointer as the value of the first argument starts searching from the saved pointer, using it as the first token. Otherwise, the subroutine's behavior does not change.