c - 在c中读取文件指针，如果EOF则返回null

Question

我是一名学生，正在制作一个函数，该函数接受文件指针(例如 stdin)并返回一个结构指针。所以我不知道如何开始。当遇到 EOF 时，它应该返回一个 null 指针。

这是我到目前为止所做的:

typedef struct book
{
    char *author;
    char *title;
    char *bookcode;
} Book;

Book *getBook(FILE *pointer)
{
    Book *p;
    int c;
    while ((c = fgetc(pointer)) != EOF)
    {
     //create book
      putchar (c);
    }
    }
    return p;
}

输入文件示例

chris evans
hello there
as2 ss1
ashley lee
big buildings
d2a 4sa

Answer 1

你大概需要这个:

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

typedef struct book
{
  char *author;
  char *title;
  char *bookcode;
} Book;

void freeBook(Book *p)
{
  free(p->author);
  free(p->title);
  free(p->bookcode);
  free(p);
}

Book *getBook(FILE *pointer)
{
  Book *p = malloc(sizeof(Book));
  p->author = NULL;
  p->title = NULL;
  p->bookcode = NULL;

  char line[200];

  if (fgets(line, sizeof(line), pointer) != NULL)
    p->author = strdup(line);

  if (fgets(line, sizeof(line), pointer) != NULL)
    p->title = strdup(line);

  if (fgets(line, sizeof(line), pointer) != NULL)
    p->bookcode = strdup(line);

  if (feof(pointer))
  {
    freeBook(p);
    return NULL;
  }
  else
    return p;
}

int main()
{
  Book *pBook;

  do
  {
    pBook = getBook(stdin);

    // do something with pBook


   freeBook(pBook);   // free memory of book if you are done with it
                      // and only if you are done with it.  
  } while (pBook != NULL);
}

免责声明:

这是基本的非错​​误检查代码，还有很大的改进空间，只是给您一个想法。