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From: chris@mimsy.UUCP
Newsgroups: comp.unix.questions
Subject: Re: Wanted: info about signal handling routines
Message-ID: <6194@mimsy.UUCP>
Date: Wed, 8-Apr-87 23:23:19 EST
Article-I.D.: mimsy.6194
Posted: Wed Apr  8 23:23:19 1987
Date-Received: Sat, 11-Apr-87 10:36:12 EST
References: <276@pluto.UUCP> <722@mcgill-vision.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 60
Keywords: sighold, sigrelse, sigset

>In article <276@pluto.UUCP>, warren@pluto.UUCP (Warren Burstein) writes:
>> I found undefined refs in a program that does job control to sighold,
>> sigrelse, and sigset.  Are they part of BSD4.2,

In article <722@mcgill-vision.UUCP> mouse@mcgill-vision.UUCP (der Mouse)
writes:
>I believe those are 4.1c -ljobs routines.

They date back to 4.1BSD.

>Under 4.2 they migrated into libc and got renamed: sighold to sigblock,
>sigrelse disappeared,

sigrelse was replaced with sigsetmask, and sigpause was not renamed at
all.

>sigset to sigvec.  The arguments also changed somewhat.

Not quite: sigvec was `internal use only except after vfork' (horrid
but true).

>>what do they do, and can I replace them with something?

Under 4.2 or 4.3BSD, use the following:

	#include <signal.h>

	#ifndef sigmask
	#define sigmask(s) (1 << ((s) - 1))
	#endif

	#define	sighold(s) (void) sigblock(sigmask(s))
	#define sigrelse(s) (void) sigsetmask(sigblock(0) & ~sigmask(s))
	#define sigset(s, d) signal(s, d)

and replace calls to

	sigpause(SIGFOO)

with

	sigpause(sigblock(0) & ~sigmask(SIGFOO))

You can save some system calls by changing code such as

	sighold(SIGCHLD);
	<stuff>
	sigrelse(SIGCHLD);

to

	int omask = sigblock(sigmask(SIGCHLD));
	<stuff>
	(void) sigsetmask(omask);

Under other operating systems, you may be stuck with no way to
handle signals reliably.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
UUCP:	seismo!mimsy!chris	ARPA/CSNet:	chris@mimsy.umd.edu