SIGINT, longjmp

Hal Murray hmurray at
Tue Jan 26 22:39:28 UTC 2016

kurt at said:
> Why do you set up a signal handler for this, and don't let the OS take care
> of it?

> Or alternativly, just call _exit() from the signal handler. 

It's not trying to exit, just get out of a long running command.

ntpq has two long-running commands.  (Maybe more.)

One is peers (which has many variants).  Normally, it tries to translate the 
IP address of the slot to a name.

The other is mrulist.  It runs in two passes.  The first pass collects the 
data. Since slots may get updated while being collected there is the 
possibility to go back and fetch them again.  The second pass sorts and 
prints things out.

With two passes, you would like ^C during the collect pass to stop collecting 
and print out what it has.  So the ^C handler just sets a flag and the 
collect loop stops collecting.  The print pass resets the flag as it starts, 
then watches the flag so another ^C will stop printing.

I think I could avoid the longjmp by having the peers loop check the flag.  I 
haven't checked to see if there are any other commands that might run too 

These are my opinions.  I hate spam.

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