正确使用Stat on C

问题描述

为什么这样做:

char *fd = "myfile.txt";
struct stat buf;          

stat(fd, &buf);
int size = buf.st_size;

printf("%d",size);

---

但这不起作用:

---

But this does not work:

char *fd = "myfile.txt";
struct stat *buf;          

stat(fd, buf);
int size = buf->st_size;

printf("%d",size);

推荐答案

之所以不起作用，是因为第一个示例中的buf分配在了堆栈上.在第二个示例中，您只有一个指向struct stat的指针，该指针指向任何地方(可能指向地址0x0，即NULL指针)，您需要为它分配内存，如下所示:

The reason for it not working is that buf in the first example is allocated on the stack.In the Second example you only have a pointer to a struct stat, pointing to anywhere (probably pointing to address 0x0, i.e. a NULL pointer), you need to allocate memory for it like this:

buf = malloc(sizeof(struct stat));

然后这两个示例都应该起作用.使用malloc()时，请务必记住在使用完struct stat之后使用free():

Then both examples should work. When using malloc(), always remember to use free() after you are finished with using the struct stat:

free(buf);

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