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From: meissner@dg_rtp.UUCP (Michael Meissner)
Newsgroups: net.unix,net.unix-wizards
Subject: Re: Not a typewriter
Message-ID: <403@dg_rtp.UUCP>
Date: Mon, 16-Jun-86 11:25:49 EDT
Article-I.D.: dg_rtp.403
Posted: Mon Jun 16 11:25:49 1986
Date-Received: Wed, 18-Jun-86 04:52:57 EDT
References: <1683@homxb.UUCP> <542@codas.ATT.UUCP>
Reply-To: meissner@dg_rtp.UUCP (Michael Meissner)
Distribution: net
Organization: Data General (Languages @ Research Triangle Park, NC.)
Lines: 23
Xref: watmath net.unix:8194 net.unix-wizards:18431

In article <542@codas.ATT.UUCP> mikel@codas.ATT.UUCP (Mikel Manitius) writes:
>> What does the sys_errlist message 'Not a typewriter' *really* mean??
>
>Errno 25 is usually generated when a program tries to execute an
>ioctl command that expects the file descriptor to be a terminal.
>(ie: you can't set the baud rate on a file).
>
>However I have also noticed that some aplications aren't very
>carefull when they use errno. For example, Informix may give
>you this message if it cannot open a database file because it
>does not exist!

    This particular error code tends to be set in errno, the first time you
use a stdio file that is not a terminal.  That is because the runtime library
wants to know if the file is associated with a terminal (so that it can be
unbuffered output in BSD or line buffered in SV.2).  Hence the library does
a isatty, which does an ioctl, and which fails, giving the error.  If an error
occurs on ioctl, isatty returns 0 instead of 1, and the library sets up to
fully buffer the file.

	Michael Meissner
	Data General Corporation
	...{ decvax, ihnp4, ucbvax }!mcnc!rti-sel!dg_rtp!meissner