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Signals with trap

Started by chakib, October 21, 2018, 02:20:10 PM

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I am preparing a small class for students on signals with trap. I understood the use of this principle with the example on signal 2 SIGINT:

trap "echo hello" 2: which displays "hello" each time you press the shortcut ctrl + c.

On the other hand, I have difficulty assimilating the use of the following cases:

1. The effect of signal 3 SIGQUIT.

2. The effect of siganl 9 SIGKILL.

3. The effect of the signal 19 SIGSTOP.

Can you guide me with simple examples please?

Best regard

Mark Greaves (PCNetSpec)

I'm pretty sure SIGKILL and SIGSTOP cannot be trapped (or handled at all).
https://www.shellscript.sh/trap.html (https://www.shellscript.sh/trap.html)
https://stackoverflow.com/questions/35569659/the-signals-sigkill-and-sigstop-cannot-be-caught-blocked-or-orignored-why (https://stackoverflow.com/questions/35569659/the-signals-sigkill-and-sigstop-cannot-be-caught-blocked-or-orignored-why)

Ctrl+\ will send a SIGQUIT signal to the terminal, so maybe
trap "bash -c /usr/bin/gedit" 3
then Ctrl+\ should fire up /usr/bin/gedit
WARNING: You are logged into reality as 'root'
logging in as 'insane' is the only safe option.