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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.unix-wizards
Subject: Re: 4.2BSD and Signals
Message-ID: <2901@umcp-cs.UUCP>
Date: Mon, 27-Jan-86 23:59:28 EST
Article-I.D.: umcp-cs.2901
Posted: Mon Jan 27 23:59:28 1986
Date-Received: Thu, 30-Jan-86 01:05:12 EST
References: <173@winston.UUCP> <174@winston.UUCP>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 22

> The man page for sig block says:
>      Signal i is blocked if the i-th bit in mask is a 1.
> well, what they really want you to do is:

 ... sigblock(1 << (signun - 1))

There is no contradiction here.  The first bit is bit 0; the 32nd
bit is bit 31; and the i'th bit is bit i-1.  I agree that the manual
should be much more explicit.  In 4.3, <signal.h> defines a macro
called `sigmask' which should be used when creating signal masks:

	omask = sigblock(sigmask(SIGINT) | sigmask(SIGHUP));
	...
	(void) sigsetmask(omask);

Note that there really should be a `signal mask' type, too; `int'
enforces a maximum of 16 signals on some machines.  Having a separate
type name would allow more than 32 signals, too.  Maybe in 4.4....
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1415)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu