signal handler output

morgon has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

as a (contrieved) example that catches SIGINT consider this:

$SIG{INT} = sub { print STDERR "*"; };

while(1) {
  sleep(1);
  print  STDERR ".";
}
[download]

When I run this in bash and press Control-C to generate a signal I get the star printed, but I also get a "^C" in the output and I don't understand where this is coming from.

So the output looks like

.....^C*...^C*....^C*..
[download]

Where do these "^C"s come from? Is this the shell, the terminal or what? And is there a way to supress that from within a perl-script?

Many thanks!

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Re: signal handler output by hippo (Bishop) on May 17, 2018 at 13:31 UTC
Is this the shell, the terminal or what? It's the shell controlling the terminal. Here's what happens in bash if I interrupt both these commands: `$ sleep 30 ^C $ stty -ctlecho; sleep 30 $` [download] As for perl, I expect IO::Stty might be able to do it but I've never used it for that.	[reply] [d/l]
Re^2: signal handler output by Anonymous Monk on May 17, 2018 at 14:50 UTC
Not the shell, it's the tty driver itself. For linux, that would be `n_tty_receive_char()` in `drivers/tty/n_tty.c`. Upon receiving the control char, it optionally echoes it.	[reply] [d/l] [select]

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