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Re: [perl #24174] perl-5.8.0-55 exit bug

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david nicol
October 13, 2003 20:51
Re: [perl #24174] perl-5.8.0-55 exit bug
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I was a little startled by this too, I thought I had been using 
sleep(0) in C to sleep until receiving an ALRM for years, and that
this idiom would fall through to perl.  Apparently you
need to set up a handler, even a null handler would work, to
catch the signal instead of the default handler, which
appears to print out "Alarm clock" and crap out.  Experiments
and results below:

[david@plaza david]$ perl -le 'sleep 0; print "slept"' &
[1] 1618
[1]   Done                    perl -le 'sleep 0; print "slept"'
[david@plaza david]$ perl -le 'sleep 9990; print "slept"' &
[1] 1622
[david@plaza david]$ kill -ALRM 1622
[david@plaza david]$ 
[1]+  Alarm clock             perl -le 'sleep 9990; print "slept"'
[david@plaza david]$ perl -le '$SIG{ALRM} = sub{ print "alarmed" } ;
sleep 9990;
 print "slept"' &
[1] 1623
[david@plaza david]$ kill -ALRM 1623
[david@plaza david]$ alarmed
[david@plaza david]$ 

On Mon, 2003-10-13 at 03:41, Doug Sibley wrote:
> says "May be interrupted if the process receives a signal such as
> SIGALRM" (as do the O'Reilly series of perl books) which led me to
> believe that I could sleep until I sent a SIGALRM at which point the
> process would continue. 
> You may wish to update either the behavior or comments of the sleep
> function.
> - Doug
> On Sat, 2003-10-11 at 09:20, Michael G Schwern wrote:
> > Doesn't seem like one to me.  The program was killed by a SIGALRM and
> > exited abnormally.  Your exit(0) is never reached.
> > 
> > perlipc states that Perl "does the default thing" to handle a signal if
> > you don't tell it otherwise.  The OS X (ie. BSD) signals(3) man page states 
> > that the default action for SIGALRM is to terminate the process.
david nicol
"In your own mind, you are the hoopiest frood. That is all that matters."
	                                               -- Gargoyle Cabbit

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