c - 列出链表

Question

我写了一个程序。它逐字地将文本文件中的数据提取到链表中。但是在列出单词时存在问题。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct list
{
    char *data;
    struct list *next;
} node;

int main()
{
    int i;
    char *word = NULL;
    char line[1000];
    node *root,*temp;

    root = (node *) malloc(sizeof(node));
    temp = root;
    FILE *f = fopen("test.txt","r");
    while (fgets( line, sizeof(line), f ))
        for (word = strtok(line, " "); word; word = strtok(NULL, " "))
        {
            temp->data = word;
            temp->next=(node *) malloc(sizeof(node));
            temp=temp->next;
        }
    fclose(f);
    temp =root;
    for(i=0; i<10; i++)
    {
        printf("%s\n",temp->data);
        temp=temp->next;
    }
    return 0;
}

Answer 1

来自'man strtok':

Be cautious when using these functions. If you do use them, note that:

   * These functions modify their first argument.
   * These functions cannot be used on constant strings.
   * The identity of the delimiting character is lost.

所以你需要为每个单词分配新的内存，因为 strtok 返回的指针正在索引到线数组中。

最好将代码更改为:

...
  while (fgets( line, sizeof(line), f )) {
    printf("%s\n",line);
    for (word = strtok(line, " "); word; word = strtok(NULL, " ")) {
      printf("%p\n",word);
      temp->data = word;
...

当在以下输入上运行时:

check default for switches 
throw stmts to exit node

打印以下内容:

check default for switches

0x7fff94e0bf70
0x7fff94e0bf76
0x7fff94e0bf7e
0x7fff94e0bf82
throw stmts to exit node

0x7fff94e0bf70
0x7fff94e0bf76
0x7fff94e0bf7c
0x7fff94e0bf7f
0x7fff94e0bf84
throw
stmts

t
throw
stmts
to
exit
node

请注意，每行中第一个单词的指针是相同的。