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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.bugs.4bsd
Subject: sendmail and others print bogus `Not a typewriter' errors
Message-ID: <8192@mimsy.UUCP>
Date: Wed, 26-Aug-87 23:17:43 EDT
Article-I.D.: mimsy.8192
Posted: Wed Aug 26 23:17:43 1987
Date-Received: Sat, 29-Aug-87 05:23:38 EDT
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 43

Index:	lib/libc/gen/isatty.c 4.3BSD Fix


Description:
	Calls to isatty(), such as those in stdio, can clobber errno,
	making later perror()s do strange things.  There are no doubt
	other library routines that do the same, but this is one of the
	more obvious.

Repeat-By:
	See, e.g., sendmail errors.

Fix:
	I chose to change isatty() itself, rather than _flsbuf().
	I doubt anything depends on errno==ENOTTY after isatty(n)==0.

RCS file: RCS/isatty.c,v
retrieving revision 1.1
retrieving revision 1.2
diff -c2 -r1.1 -r1.2
*** /tmp/,RCSt1007512	Wed Aug 26 23:13:55 1987
--- /tmp/,RCSt2007512	Wed Aug 26 23:13:55 1987
***************
*** 12,18 ****
  {
  	struct sgttyb ttyb;
  
! 	if (ioctl(f, TIOCGETP, &ttyb) < 0)
  		return(0);
  	return(1);
  }
--- 12,22 ----
  {
  	struct sgttyb ttyb;
+ 	extern int errno;
+ 	int olderr = errno;
  
! 	if (ioctl(f, TIOCGETP, &ttyb) < 0) {
! 		errno = olderr;
  		return(0);
+ 	}
  	return(1);
  }
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	seismo!mimsy!chris