Test if stdin has input for C++ (windows and/or linux)

Question

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.

Answer 1

Would this not work?

std::cin.rdbuf()->in_avail();

Answer 2

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\n");
        else if(ret == 0)
                printf("No\n");
        else
                printf("Error\n");
        return 0;
}

Testing:

$ ./stdin
No
$ echo "foo" | ./stdin
Yep

Answer 3

I'm not sure, but does _kbhit() do what you need?