Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!pasteur!agate!ig!uwmcsd1!bbn!rochester!srs!dan
From: dan@srs.UUCP (Dan Kegel)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Checking for KBD input in "raw" mode
Message-ID: <621@srs.UUCP>
Date: 2 Mar 88 18:21:34 GMT
References: <8281@eddie.MIT.EDU> <5341@well.UUCP>
Reply-To: srs!dan@cs.rochester.edu
Distribution: na
Organization: S.R.Systems
Lines: 18

Ed Nather asked
> How do you check to see if there are any characters ready on stdin in RAW 
> mode?  The ususal int 21, ah=0bh (Check Stdin Status) is vulnerable to ^C.

In article <5341@well.UUCP> gam3@well.UUCP (G. Allen Morris III) writes:
> use int 21h function 4402h (IOCTL Read).

This is wrong; none of the usual devices distributed with MS-DOS can do
IOCTL reads or writes.

Perhaps Morris meant int 21h function 4406h (IOCTL Check Input Status), e.g.
    mov ax, 4406h
    mov bx, 0		; fileno(stdin)
    int 21h
    ; AL = 0 if no characters waiting, ffh if at least one char ready.
This works even when stdin is redirected to a file.
-- 
  Dan Kegel
  srs!dan@cs.rochester.edu rochester!srs!dan dan%srs.uucp@SOL.cs.rochester.edu