Re: Lua and signals

[Bernd Eggink <monoped@...>]

On 26.12.2012 16:34, Bernd Eggink wrote:

> I wonder if signal handling (as in luaposix) is supposed to work in any
> situation. Or are there limitations, preconditions etc.(on Linux)?
>
> I'm asking because I have a program where signal() simply doesn't work.
> After putting
>
>      local P = require "posix"
>      P.signal(P.SIGUSR1, function() print("signal") end)
>
> at the beginning of the program, I expect the command "kill -s USR1
> $pid" to print "signal", but instead the program exits immediately. This
> even happens when the signal handling function is completely empty.
>
> The program in question is pretty complex. However, in simple test
> programs signal() works as expected.

Thanks for your replies.
I investigated a bit further. As my program uses a kind of UI whose 
event loop is essentially driven by io.read() results,  I tried the 
following little program:

-----------------------------
local P = require "posix"

P.signal(P.SIGUSR1, function(s)
    print("Got signal", s)
end)

print(P.getpid("pid"))
os.execute("stty -echo cbreak")		-- [1]
while true do print(io.read()) end
-----------------------------

Here the signal handling works, but the output is:

Got signal      10
nil     Interrupted system call 4

Interestingly, the "Interrupted system call" disappears if the line 
marked [1] is commented out. OTOH, if I comment out the stty command in 
the original program, the signal still isn't caught, so this may be a 
red herring.

Regards,
Bernd