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From: wnp@killer.UUCP (Wolf Paul)
Newsgroups: comp.sys.ibm.pc,comp.lang.c
Subject: Determining if a file is a device
Message-ID: <1738@killer.UUCP>
Date: Mon, 5-Oct-87 11:31:12 EDT
Article-I.D.: killer.1738
Posted: Mon Oct  5 11:31:12 1987
Date-Received: Fri, 9-Oct-87 04:31:07 EDT
Organization: The Unix(R) Connection, Dallas, Texas
Lines: 23
Keywords: stat(2), MS-DOS devices
Xref: mnetor comp.sys.ibm.pc:8722 comp.lang.c:4740

In trying to implement a function which emulates the UNIX stat(2)
system call I have run into a problem:

How can I determine whether a filename passed to a C function
is a regular file or the name of a device?

I realize that I could hard-code the default device names (i.e. CON,
PRN, COM1, LPT1, etc.) into my function, but that would fail as soon
as there were a user-installed device driver using a non-standard name.

Is there a DOS function which will let me determine this? Can the DOS
IOCTL function be used without opening the named file?

In a related question, given a file handle (file descriptor), is there
any way to determine the name of the file? Specifically, can I determine
which device file handle 0 (STDIN) refers to, i.e. CON or possibly COM1?
This would be required to implement a tty(1) command, to determine
whether access is local (via th CONsole), or remotely, via a COM port.

Thanks for any hints - please post or e-mail as you see fit.

Wolf Paul
ihnp4!killer!wnp