c - 关闭无效的文件描述符有什么作用？

Question

我有一些遗留代码可以到处执行此操作:

int fd; // open a file 

if(fd == -1)
{
    close(fd);
}

我觉得这很不对。

关闭无效的文件描述符是否有效？

Answer 1

根据手册:

Upon successful completion, a value of 0 is returned. Otherwise, a value of -1 is returned and the global integer variable errno is set to indicate the error.

然后:

 The close() system call will fail if:

 [EBADF]            fildes is not a valid, active file descriptor.

那么就不会发生任何有害的事情了。