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From: m5d@bobkat.UUCP
Newsgroups: comp.unix.questions
Subject: Re: Shell doesn't pass modified signal mask to sub-processes
Message-ID: <853@bobkat.UUCP>
Date: Thu, 9-Apr-87 09:37:08 EST
Article-I.D.: bobkat.853
Posted: Thu Apr  9 09:37:08 1987
Date-Received: Sun, 12-Apr-87 03:27:39 EST
References: <319@baskin.UUCP>
Reply-To: m5d@bobkat.UUCP (Mike McNally (Man Insane))
Organization: Digital Lynx, Inc; Dallas, TX
Lines: 37
Keywords: ...and I want it to!  Is there a work-around?

In article <319@baskin.UUCP> wmk@baskin.UUCP (Bill Kules) writes:
>I've "discovered," much to my dismay, that the Bourne shell does
>not let me pass the modified signal mask to the sub-processes it
>spawns; it only passes the original one.  (We have a Gould 6040
>running UTX/32 1.2, a BSD 4.2 system with a little Sys V.)
>
>The situation is:  I run a C program that sets the signal mask
>to ignore interrupt and quit signals.  It then calls a /bin/sh
>script.  Within that script I reset the mask (i.e., trap 2 3)
>and then call another C program.  The mask being passed to that
>program still ignores SIGINT and SIGQUIT.
>
>Thanks in advance,
>-- 
>Bill Kules                        "We're on the road
>...seismo!vrdxhq!baskin!wmk       and we're gunning for the Buddha"
>...decuac!baskin!wmk                     -- Shriekback

There is a difference between the signal mask and the mechanism by
which signals are ignored.  The call

	signal(SIGBLAH, SIG_IGN);

does nothing at all to the signal mask.  The mask is set with
sigblock() or sigsetmask() (or sort of with sigvec()).  Notice
also that the man page for sh says that "trap" with a missing 
command resets the signals to their original value -- that is,
the value the shell found upon entry.  This value is of course
SIG_IGN, since the parent C program set that.  Why not try
removing the "trap" statement from the script?


-- 
Mike McNally, mercifully employed at Digital Lynx ---
    Where Plano Road the Mighty Flood of Forest Lane doth meet,
    And Garland fair, whose perfumed air flows soft about my feet...
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