为什么 explain_fwrite 说我的文件标记为非阻塞？

Question

我正在尝试将一些数据写入文件。 fwrite 正在返回 EAGAIN 并且 fwrite_explain 说：

2: fwrite(ptr = 0x7F41EFBC09A8, size = 4066, nmemb = 1, fp = 0x02F79200 "/home/user/asdf.txt") failed, Resource temporarily unavailable (11, EAGAIN) because the file descriptor has been marked non-blocking (O_NONBLOCK) and the write would block
2: fwrite(ptr = 0x17ECFFA40, size = 4066, nmemb = 1, fp = 0x02F79200 "/home/user/asdf.txt") failed, No such file or directory (2, ENOENT) because the file is on a file system ("/home", 1% full) which does not support Unix open file semantics, and the file has been deleted from underneath you
2: fwrite(ptr = 0x17ECFF100, size = 4066, nmemb = 1, fp = 0x02F79200 "/home/user/asdf.txt") failed, No such file or directory (2, ENOENT) because the file is on a file system ("/home", 1% full) which does not support Unix open file semantics, and the file has been deleted from underneath you

我假设第二组警告无效（文件永远不会被删除，它仍然存在）。

我从不将我的文件设置为非阻塞，我不在乎它是否阻塞，因为我想写入数据，不管它可能需要多长时间。什么给了？

相关代码：

fd = fopen(file_to_write, "w");
if (fd == NULL) printf("%d could not open file\n", errno);
n = fwrite((void*)h->bufs[i], write_size, 1, fd);
if (n != write_size) {
    printf("%d: %s\n", errno, explain_fwrite((void*)h->bufs[i], write_size, 1, fd));

Answer 1

fwrite() 返回写入的 items 数量，而不是一个项目的 size 或两者的乘积。 （仅当一项的大小恰好为 1 时，返回值才等于写入的字节数。）

解决方案是与您尝试编写的项目数量进行比较：

n = fwrite((void*)h->bufs[i], write_size, 1, fd);
if (n != 1) {

注意：在调用之前将errno 设置为零可能是明智的，因为如果函数没有错误，它不会设置为零。

Answer 2

我在发布这个的过程中设法解决了这个问题。原来fwrite 对 size 和 nmemb 的顺序和内容很挑剔。我想我可以写一个 非常大的成员，但它不是这样工作的。我必须以一个字节的大小写write_size 成员。