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Tech Zone => Programming => Topic started by: chakib on October 21, 2018, 02:20:10 pm

Title: Signals with trap
Post by: chakib on October 21, 2018, 02:20:10 pm
Hello,

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
Title: Re: Signals with trap
Post by: Mark Greaves (PCNetSpec) on October 21, 2018, 10:34:13 pm
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)
and
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
Code: [Select]
trap "bash -c /usr/bin/gedit" 3
then Ctrl+\ should fire up /usr/bin/gedit
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