[GD-General] OT: Checking if any chars available on stdin under Windows

[Colin F. <cp...@ea...>]

2004 April 22nd
Friday

Off-Topic question here...but I just spent an hour doing Google
searching and reading other online documentation, and I'm not
finding any answers to the following:

QUESTION:  How can I check if stdin (standard input) has any 
characters available for reading under WINDOWS (not Linux)?

I thought (cin.rdbuf()->in_avail()) would be the cool hacked
solution -- but even after doing Sleep(1000), cin.sync_with_stdio(),
and wackier and wackier things to try to make "cin" up-to-date,
so to speak, the expression above ALWAYS yields zero, whether or
not there are characters available on the input stream.
(Compiled using Visual C++ 6.0 under Windows 2000)

If I have a command line like the following:

        testapp

then the following code blocks indefinitely:

        int c = cin.peek();

but if the command line is as follows:

        more textfile.txt | testapp

then the application does not block.  But in both
cases (cin.rdbuf()->in_avail()) is zero.

How can "testapp" in the two command line examples
above DETECT which scenario (piped input or not) is
involved?  That, I guess, is my real goal.  I want to
know if the command line lacks the piping from 
another app, since this means I shouldn't wait 
forever for stdin data.

I'd be willing to use a Win32 function to solve this
problem, but if it is really tricky, like creating a
thread, or something nutty, then it's probably not
worth it.  Bleah, under Linux one can actually use
fnctl() to change stdin to non-blocking mode (but,
I assume, still buffered), which makes this problem
go away -- but no fnctl() under Windows.

Anyhow, probably avoiding piping data through stdin
is the REAL solution to all of this mess, but that
decision is not mine to make.

--- Colin