4.2BSD and Signals

[Chris Torek]

> 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)
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