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Re: [Chicken-users] question about signal handler

From: felix
Subject: Re: [Chicken-users] question about signal handler
Date: Sun, 6 Oct 2002 22:35:38 +0200

>it appears that on my system the signal handling is performing in a
>very strange way.
>In my understanding, the program below, being compiled and started,
>should print "hello" and exit when I send it the SIGHUP signal. It
>does not. Instead, it prints "hello" when the "sleep" is finished
>(either after 30 secs or being killed). I tried also
>process-run/process-wait combination - with a similar result.
>Will be very appreciated for your help.
>OS:          various x86 Linux'es
>Compilation: csc -o signal_test signal_test.scm
>;===== signal_test.scm ======
>(declare (uses posix)
>         (interrupts-enabled))
>(set-signal-handler! signal/hup (lambda (s) (display "hello\n") (exit)))
>(system "sleep 30")

The problem here is that, by evaluating (system "sleep 30"), you
dont't really send the current process to sleep, but a different
one (spawned by the shell). You can see this is you enter
"signal_test &" at the shell and look at the list of running processes
with "ps". To make your code work, you have to invoke the `sleep'
function directly:

(define sleep (foreign-lambda int "sleep" int))

(sleep 30)

(The newest CVS version of Chicken has `sleep()' (posix library unit))


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