在 C 中使用 strtok 比较单词

Question

我已经开始学习 c。目前，我正在尝试从两个 char 数组中提取单词，以便可以使用名为 compare 的辅助方法来比较它们。但是，我的 strtok() 给了我奇怪的输出。 这是我的代码：

char *headerPointer=headers;
    char *linePointer=firstline;
    printf("Header-%s\n",headers);
    printf("Line-%s\n",firstline);
    headerPointer=strtok(headerPointer,",");
    linePointer=strtok(linePointer,",");
    while ((headerPointer!=NULL&&linePointer!=NULL)) {
            printf("\nPrinting words from headers\n");
            printf("%s",headerPointer);
            headerPointer=strtok(NULL,",");
            printf("\nPrinting words from line\n");
            printf("%s",linePointer);
            linePointer=strtok(NULL, ",");

        }

以上代码产生的输出：

Header-Hello,My,name,is,Ram.
Line-I,own,20,thousand,bucks.

Printing words from headers-
Hello.
Printing words from line-
I.
Printing words from headers-
own.
Printing words from line-
20.
Printing words from headers-
thousand.
Printing words from line-
bucks.

我不明白为什么 header 打印行中的内容以及 my,name,is,ram 去哪里？

我尝试使用以下代码编写它们，并且相同的代码产生了所需的输出。 不同的代码风格：

char *headerPointer=headers;
    char *linePointer=firstline;
    printf("Header%s\n",headers);
    printf("Line%s\n",firstline);
    headerPointer=strtok(headerPointer,",");

        while(headerPointer!=NULL)
    {
        printf("\nPrinting words from headers\n");
        printf("%s",headerPointer);
        headerPointer=strtok(NULL,",");

    }
    linePointer=strtok(linePointer,",");

    while(linePointer!=NULL){
        printf("\nPrinting words from line\n");
        printf("%s",linePointer);
        linePointer=strtok(NULL, ",");
    }

输出：

Header-Hello,My,name,is,Ram.
Line-I,own,20,thousand,bucks.

Printing words from headers-
Hello.
Printing words from headers-
My.
Printing words from headers-
name.
Printing words from headers-
is.
Printing words from headers-
Ram.
Printing words from line-
I.
Printing words from line-
own.
Printing words from line-
20.
Printing words from line-
thousand.
Printing words from line-
bucks.

请解释为什么基于相同想法的两个代码会产生不同的结果？我们可以修改第一个代码以给出类似第二个的结果吗？我试图搜索并遵循已经可用的解决方案，但无法走远。

Answer 1

strtok 是有状态且不可重入的；它一次只能标记一个字符串。在您的原始代码中，您试图同时标记两个输入，但它不能这样做；它只是沿提供的最后一个非NULL 字符串参数进行标记，即linePointer。

要完成这项工作，您需要使用strtok_r，它允许您保存每个字符串的进度，而不会覆盖另一个字符串的进度。