Re: Background processes receive SIGINT even though they shouldn't

[Ingemar Nilsson]

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Chet Ramey wrote:

> I think you're slightly misunderstanding how job control and process
> groups interact.

Okay.

> When you run test1 from an interactive shell with job control enabled,
> it is placed into a separate process group.  The terminal's foreground
> process group is set to test1's process group, which means that group
> receives keyboard-generated signals like SIGINT.
> 
> The shell started to run test1 is not interactive, so job control is
> disabled.  This means that all processes started by test1 and its
> descendants are placed into the same process group.  Since this is
> the terminal's foreground process group, these processes receive the
> SIGINT.

I see, thanks. Then I have another question: Why does test2 below fail
to trap SIGINT when started by test1? It works when I run test2 directly.

test1 (for reference):

### START SCRIPT ###
#!/bin/bash

test2 &

while /bin/true; do
    echo test1 sleeping
    sleep 5
done
### END SCRIPT ###

test2 (updated):

### START SCRIPT ###
#!/bin/bash

function shutdown {
    echo "Shutting down test2..."
    exit 0
}

trap shutdown SIGINT

while /bin/true; do
    echo test2 sleeping
    sleep 5 &
    SLEEP_PID=$!
    wait $SLEEP_PID
    unset SLEEP_PID
done
### END SCRIPT ###

Thanks in advance.
Regards
Ingemar
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