问题描述
我基本上想测试 stdin 是否有输入(就像你回声和管道输入一样).我找到了有效的解决方案,但它们很丑陋,我喜欢我的解决方案干净.
I basically want to test if stdin has input (like if you echo and pipe it). I have found solutions that work, but they are ugly, and I like my solutions to be clean.
在 linux 上我使用这个:
On linux I use this:
bool StdinOpen() {
FILE* handle = popen("test -p /dev/stdin", "r");
return pclose(handle) == 0;
}
我知道我应该添加更多的错误处理,但这不是重点.
I know that I should add more error handling, but it's besides the point.
在 Windows 上我使用这个:
On windows I use this:
bool StdinOpen() {
static HANDLE handle = GetStdHandle(STD_INPUT_HANDLE);
DWORD bytes_left;
PeekNamedPipe(handle, NULL, 0, NULL, &bytes_left, NULL);
return bytes_left;
}
这对 linux 来说很好,但我想知道我可以在不使用管道的情况下调用的等效 API 是什么(例如对于 test -f $file
,您执行 fopen($文件,"r") != NULL
).我有一种暗示,我可以 open("/dev/stdin", "r")
并做同样的事情,但我想知道最好的方法.
That is fine for linux, but I want to know what are the equivalent APIs that I can call without using a pipe (like for test -f $file
you do fopen($file, "r") != NULL
). I have an inkling that I could open("/dev/stdin", "r")
and do the same thing, but I want to know the best way to do it.
总结:我想知道我可以用来代替 Linux 的 test -p/dev/stdin
的 API,如果你知道更好的解决方案窗户.
Summary: I want to know the APIs I could use to substitute for test -p /dev/stdin
for linux, and, if you know a better solution for windows.
推荐答案
这是 POSIX (Linux) 的解决方案:我不确定 Windows 上的 poll() 等价物是什么.在 Unix 上,编号为 0 的文件描述符是标准输入.
Here's a solution for POSIX (Linux): I'm not sure what's the equivalent of poll() on Windows. On Unix, The file descriptor with number 0 is the standard input.
#include <stdio.h>
#include <sys/poll.h>
int main(void)
{
struct pollfd fds;
int ret;
fds.fd = 0; /* this is STDIN */
fds.events = POLLIN;
ret = poll(&fds, 1, 0);
if(ret == 1)
printf("Yep
");
else if(ret == 0)
printf("No
");
else
printf("Error
");
return 0;
}
测试:
$ ./stdin
No
$ echo "foo" | ./stdin
Yep
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