在C中读取特定模式的txt文件

huangapple
go评论98阅读模式
英文:

Reading a specific pattern of a txt file in C

问题

以下是您提供的内容的翻译：

  1. 我有一个带有以下模式的txt文件：

11/01/2010：没有通过考试！:(
5
10/02/2010：甚至这次我也没有通过！>:(
2
16/04/2010：这是我第三次重考这门考试！>:@
1
20/05/2024：终于通过了！:D
14

  1. 我必须将文件中的每个实例放入一个如下定义的队列数据结构中：
  2. ``` c
  3. struct post {
  4.     char msg[257];
  5.     int n_like;
  6. };
  8. struct feed {
  9.     struct post* storage;
  10.     int busy;
  11. };
  13. void init(struct feed* queue) {
  14.     queue->storage = malloc(sizeof(struct post) * N_QUEUE); //N_QUEUE = 4
  15.     queue->busy = 0;
  16. }

为此，我尝试了以下函数，在该函数中，我使用fgets()读取第一整行，然后使用fscanf()读取下面的数字。然后通过append()存储所有内容：

  1. int append(struct feed* queue, struct post s) {
  2.     if (queue->busy >= N_QUEUE) return handle_err(FULL);
  3.     queue->storage[queue->busy] = s;
  4.     queue->busy++;
  5.     return OK;
  6. }
  8. struct post pop(struct feed* queue) {
  9.     if (queue->busy <= 0) handle_err(EMPTY);
  10.     struct post s = queue->storage[0];
  11.     for (int i = 0; i < queue->busy - 1; i++) {
  12.         queue->storage[i] = queue->storage[i + 1];
  13.     }
  14.     queue->busy--;
  15.     return s;
  16. }
  18. int load_user_from_file(char* filename, struct feed* queue) {
  19.     FILE *fp = fopen(filename, "r");
  20.     if (fp == NULL) return handle_err(FILE_ERR);
  22.     struct post s;
  23.     while (fgets(s.msg, 257, fp) != NULL) {
  24.         while (fscanf(fp, "%d", &s.n_like) == 1) {
  25.             append(&(*queue), s);
  26.         }
  27.     }
  28.     return OK;
  29. }

主函数：

  1. int main() {
  2.     struct feed queue;
  3.     init(&queue);
  4.     char* filename = "user42.txt";
  5.     load_user_from_file(filename, &queue);
  7.     return 0;
  8. }

如果我让程序运行，我当然会得到空字符串和零。但是，如果包括handle_err()，该函数只会在屏幕上触发错误并退出。

  1. int handle_err(int errno) {
  2.     switch (errno) {
  3.         case FILE_ERR:
  4.             printf("\nerror (%d): 无法写入/读取文件\n\n", FILE_ERR);
  5.             break;
  6.         case EMPTY:
  7.             printf("\nerror (%d): 队列为空\n\n", EMPTY);
  8.             break;
  9.         case FULL:
  10.             printf("\nerror (%d): 队列已达到其最大容量\n\n", FULL);
  11.             break;
  12.         default: printf("\n发生未知错误\n\n");
  13.     }
  14.     exit(FALSE);
  15. }

我相当确定load_user_from_file函数中有问题。

英文:

I have a txt file with this pattern:

  1. 11/01/2010: did not pass the test! :(
  2. 5
  3. 10/02/2010: not even this time I passed it! &gt;:(
  4. 2
  5. 16/04/2010: is the third time I retake this exam!!! &gt;:@
  6. 1
  7. 20/05/2024: finally passed it! :D 
  8. 14

I have to put every instance in the file in a queue data structure so defined

  1. struct post {
  2. 	char msg[257];
  3. 	int n_like;
  4. };
  6. struct feed {
  7. 	struct post* storage;
  8. 	int busy;
  9. };
  11. void init(struct feed* queue) {
  12. 	queue-&gt;storage = malloc(sizeof(struct post) * N_QUEUE); //N_QUEUE = 4
  13. 	queue-&gt;busy = 0;
  14. }

To do this I tried this function, where I read the first whole line using fgets() and then the number below with fscanf(). Then storing everythin through append():

  1. int append(struct feed* queue, struct post s) {
  2. 	if (queue-&gt;busy &gt;= N_QUEUE) return handle_err(FULL);
  3. 	queue-&gt;storage[queue-&gt;busy] = s;
  4. 	queue-&gt;busy++;
  5. 	return OK;
  6. }
  8. struct post pop(struct feed* queue) {
  9. 	if (queue-&gt;busy &lt;= 0) handle_err(EMPTY);
  10. 	struct post s = queue-&gt;storage[0];
  11. 	for (int i=0; i&lt;queue-&gt;busy-1; i++) {
  12. 		queue-&gt;storage[i] = queue-&gt;storage[i+1];
  13. 	}
  14. 	queue-&gt;busy--;
  15. 	return s;
  16. }
  18. int load_user_from_file(char* filename, struct feed* queue) {
  19. 	FILE *fp = fopen(filename, &quot;r&quot;);
  20. 	if (fp == NULL) return handle_err(FILE_ERR);
  21. 	
  22. 	struct post s;
  23. 	while (fgets(s.msg, 257, fp) != NULL) {
  24. 			while (fscanf(fp, &quot;%d&quot;, &amp;s.n_like) == 1) {
  25. 				append(&amp;(*queue), s);
  26. 			}
  27. 		}
  28. 	return OK;
  29. }

main:

  1. int main() {
  2. 	struct feed queue;
  3. 	init(&amp;queue);
  4. 	char* filename = &quot;user42.txt&quot;; 
  5. 	load_user_from_file(filename, &amp;queue);
  7. 	return 0;
  8. }

If I let the program run I get, of course, empty strings and zeros. Instead by including the handle_err(), which just triggers errors on screen and exits, I get a full stack error.

  1. int handle_err(int errno) {
  2. 	switch (errno) {
  3. 		case FILE_ERR:
  4. 			printf(&quot;\nerror (%d): could not write/read the file\n\n&quot;, FILE_ERR);
  5. 			break;
  6. 		case EMPTY:
  7. 			printf(&quot;\nerror (%d): queue is empty\n\n&quot;, EMPTY);
  8. 			break;
  9. 		case FULL:
  10. 			printf(&quot;\nerror (%d): queue reached its full space\n\n&quot;, FULL);
  11. 			break;
  12. 		default: printf(&quot;\nunknown error occurred\n\n&quot;);
  13. 	}
  14. 	exit(FALSE);
  15. }

I'm pretty sure there's something wrong in the load_user_from_file function.

答案1

得分: 1

Your code is incomplete, but the corrected portion is as follows:

  1.     while (fgets(s.msg, 257, fp) != NULL)
  2.     {
  3.         char buf[100];
  4.         if ( (fgets(buf, sizeof(buf), fp) != NULL) 
  5.           && (sscanf(buf, "%d", &s.n_like) == 1)
  6.         {
  7.            append(&(*queue), s);
  8.         }
  9.         else
  10.         {   // Adjust error handling for your needs.
  11.             exit(1);
  12.         }
  13.     }

Please note that this code corrects the issue with fscanf and parses the input as intended.

英文:

While your code is not complete, this is clearly wrong:

  1.     while (fgets(s.msg, 257, fp) != NULL) {
  2.             while (fscanf(fp, &quot;%d&quot;, &amp;s.n_like) == 1) {
  3.                 append(&amp;(*queue), s);
  4.             }
  5.         }

With the given input file that will result in more entries than you want to.

With

  1. 11/01/2010: did not pass the test! :(
  2. 5
  3. 10/02/2010: not even this time I passed it! &gt;:(
  4. 2

The fscanf will first parse 5 and then also 10, leaving &quot;/02/2010: not even this time I passed it! &gt;:(\n&quot; for the next entry.

In total you will append 7 structs instead of 4.

As you have a clear relation of one line with date+text and one line with that integer, it does not make any sense to use fscanf in a loop.

Try something like this:

  1.     while (fgets(s.msg, 257, fp) != NULL)
  2.     {
  3.         char buf[100];
  4.         if ( (fgets(buf, sizeof(buf), fp) != NULL) 
  5.           &amp;&amp; (sscanf(buf, &quot;%d&quot;, &amp;s.n_like) == 1)
  6.         {
  7.            append(&amp;(*queue), s);
  8.         }
  9.         else
  10.         {   // Adjust error handling for your needs.
  11.             exit(1);
  12.         }
  13.     }

huangapple
  • 本文由 发表于 2023年6月12日 18:32:48
  • 转载请务必保留本文链接：https://go.coder-hub.com/76455781.html
  • c
  • data-structures
  • fgets
  • queue
  • struct
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