Re: [Help-bash] readline does not always handle SIGTERM on reboot

[Chet Ramey]

On 4/6/18 8:03 PM, john smith wrote:

>> First of all, bash ignores SIGTERM when it's interactive, so if you don't
>> happen to send SIGTERM while readline is reading a command, you're not
>> going to get anything. (There is a recent post on bug-bash explaining why
>> readline returns EOF when it gets SIGTERM.)
> 
> Thanks, you helped me understand something.  I discovered that the
> above program would logout the current session I ran it in if I ran it
> in the background from another program like that:
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> 
> int main(void)
> {
>   if(fork() == 0)
>     {
>       execv("/bin/kill-mine", NULL);
>     }
> }
> 
> Or put daemon() at the top:
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <signal.h>
> #include <unistd.h>
> 
> int main(void)
> {
>   daemon(0, 0);
>   kill(-1, SIGTERM);
> 
>   return EXIT_SUCCESS;
> }
> 
> Or simply run it with &:
> 
> $ kill-mine &
> 
> So the general conclusion is that it has be detached from the terminal
> before sending SIGTERM to bash.  I still don't know answers for 2
> questions:
> 
> 1. Where is the above checked in bash?

Sorry, the above what?

> 2. Why does busybox reboot make bash logout occasionally even if it
> theoretically shouldn't because it does not detach from terminal?  

I don't run busybox, so I won't speculate. My first guess would be that
the signal comes in while bash is ignoring SIGTERM (by catching the signal
and discarding it).

-- 
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    address@hidden    http://tiswww.cwru.edu/~chet/