nonblocking read from stdin

Question

I expect ReadConsoleW() to return after reading a specific number of bytes. But it doesn't return.

How can I make ReadConsoleW() return as soon as it finished reading the number of bytes specified?

The code I tried is here:

#include <stdio.h>
#include <Windows.h>


int main()
{
    //something is being written to stdin.
    Sleep(2000);
    int b;
    int r;
    //read 3 wide character
    ReadConsoleW(GetStdHandle(STD_INPUT_HANDLE), &b, 3*sizeof(TCHAR), (LPDWORD)&r, NULL);
    //problem: no returns until enter pressed
    putc(b,stdout);
    while(1)
    {};
}

score 2 · Accepted Answer · answered Feb 04 '13 at 05:05

2

Use SetConsoleMode to turn off ENABLE_LINE_INPUT flag. No line editing will be available, but it won't wait until the Enter is pressed.

Note that you can't read three WCHARs into an int.

answered Feb 04 '13 at 05:05

Anton Kovalenko

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but still it will wait for at least _one_ character in the buffer... i.e. it is still blocking read. – Agnius Vasiliauskas Feb 04 '13 at 07:55
2

`PeekConsoleInput` is non-blocking, but you have to use `ReadConsoleInput` to consume the input (or check input event types to be sure that `ReadConsoleChars` won't block). (And whenever you want to wait for console events with timeout, just `WaitForSingleObject` on console handle). – Anton Kovalenko Feb 04 '13 at 09:28

score -2 · Answer 2 · answered Feb 04 '13 at 12:10

-2

Consider also asynchronous I/O in Windows using ReadFile/WriteFile. See MSDN on asynchronous I/O

It is a little more complicated, but you do have what you want.

answered Feb 04 '13 at 12:10

bash.d

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It [does not work](http://stackoverflow.com/questions/4551644/using-overlapped-io-for-console-input) for console handles. – Anton Kovalenko Feb 04 '13 at 12:52

nonblocking read from stdin

2 Answers2