i386/71893

[Dag-Erling Smørgrav]

The following reply was made to PR i386/71893; it has been noted by GNATS.

From: des at des.no (=?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?=)
To: freebsd-gnats-submit at freebsd.org
Cc:  
Subject: Re: i386/71893
Date: Mon, 27 Sep 2004 15:14:17 +0200

 isatty(3) is a library function, not a system call.  Its return value
 is not a success / failure indication like that of system calls, but a
 yes / no answer.  It is allowed, but not required, to set errno when
 it determines that the specified file descriptor does not correspond
 to a terminal device.
 
 In more general terms, you can not make any assumptions about the
 value of errno except immediately after a failed system call; its
 value is undefined in all other circumstances.  System calls that do
 not fail leave it untouched, but library functions may or may not
 modify it, and its value may or may not reflect the actual error
 experienced by the library function.
 
 For more details on errno and isatty(3), refer to the Open Group Base
 Specification.
 
 DES
 --=20
 Dag-Erling Sm=F8rgrav - des at des.no