strtok() 获取字符串的第一个标记时出现问题
以下代码无法获取字符串的第一个标记：
char *p1;
char array[100];
strcpy(array, "ANY STRING WOULD DO");
p1 = strtok(array, " ");
p1 = strtok(NULL, " ");
p1 = strtok(array, " ");
p1 = strtok(NULL, " ");
printf("%c", p1);
The following code fails to get me the first token of the string:
char *p1;
char array[100];
strcpy(array, "ANY STRING WOULD DO");
p1 = strtok(array, " ");
p1 = strtok(NULL, " ");
p1 = strtok(array, " ");
p1 = strtok(NULL, " ");
printf("%c", p1);
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评论（5）
strtok()实际上用文字“\0”替换分隔符 - 实际上是覆盖原始字符串。第二次调用strtok(array, "");时，array现在看起来像ANY'\0'STRING'\0' 都可以
（例如，如果您要打印字符串，您只会看到“ANY”）
由于 strtok 不会超出字符串末尾，因此您第二次只会获得一个标记，并且调用
strtok(NULL, “”);返回NULL。要解决您的问题，您需要将字符串复制到另一个位置以进行第二组操作，或者保存临时字符串指针。strtok()actually replaces the delimiters with a literal '\0' - in effect writing over your original string. The second time you callstrtok(array, "");,arraynow looks likeANY'\0'STRING'\0'WOULD DO
(e.g. if you were to print the string, you'd just see "ANY")
Since strtok doesn't go beyond the end of a string, you'll only get the one token the second time around, and the call to
strtok(NULL, " ");returnsNULL. To overcome your problem, you need to either copy the string into another location for the second set of operations, or save a temporary string pointer.请查看此处给出的示例： MSDN: strtok , wcstok, _mbstok
Please take a look at the example given here: MSDN: strtok, wcstok, _mbstok
这可行：
strtok 修改它传递的字符串，因此如果您想重新解析它，您需要再次复制它。
如果您只想保留令牌，只需复制指针即可。
This would work:
strtok modifies the string it is passed so if you want to re-parse it you need to copy it again.
If you just want to keep the tokens, just copy the pointers.
请记住，
strtok通过在每个标记后面放置'\0'字符来修改字符串。因此，当您尝试再次标记同一字符串时，实际上只是标记了第一个标记。
这将导致第二个
p1 = strtok(NULL, " ");将返回NULL，当您尝试打印 p1 时，它会尝试取消引用NULL，并且可能会失败。请注意，您需要使用
"%s"而不是"%c"，因为您打印的是字符串，而不是字符。Remember that
strtokmodifies the string by placing'\0'characters after every token.So, when you try tokenizing the same string again, you're really tokenizing the first token only.
This will have as a result that the second
p1 = strtok(NULL, " ");will returnNULL, and when you then try to print p1, it'll try to dereferenceNULL, and probably fail.Note btw, that you need to use
"%s"instead of"%c", because you're printing a string, not a character.strtok()实际上是通过在找到标记末尾时添加零终止符 ('\0') 来修改您要在其中查找标记的字符串。所以迭代完之后，它就不再是内存中的连续字符串了。这就是为什么您不能从头开始并重新解析字符串中的标记的原因。您可能有两种选择：
首先复制字符串，然后对其进行标记
或者您可以在找到它们时保留指向单独标记的指针数组，然后重新使用数组，而不是重新调用
strtok()。strtok()actually modifies the string you are looking for tokens in by adding zero-terminator characters ('\0') to it when it finds the end of a token. So after iterating through it, it is no longer a continuous string in memory anymore. This is why you can not start again at the beginning and re-parse the string for tokens.You probably have two choices:
make a copy of the string first and tokenise that instead
or you could keep an array of pointers to the separate tokens as you find them and re-use the array, rather than re-calling
strtok().