Re: [Bug-ddrescue] 2 Suggestions (bi-directional retry and user interruption exit code)

[Antonio Diaz Diaz]

Scott D wrote:
> Hmmm, maybe we don't need a separate exit code if ddrescue was 
> terminated. Found some really useful information at 
> http://www.cons.org/cracauer/sigint.html. Try out the following bash 
> script, editing for your proper ddrescue command:
>
> > #!/bin/bash
> > trap 'echo ddrescue was terminated by the user; exit' 2
> > ddrescue -f /dev/sdc /dev/null -s 1G
> > echo ddrescue exited normally
> > exit

The site is very useful indeed, but your proposed script is of type 
"immediate unconditional exit", which leaves ddrescue:
"in an unusable state, since the death of its calling shell will leave 
it without required resources (file descriptors). This way does not work 
at all for shellscripts that call programs that use SIGINT for other 
purposes than immediate exit. Even for programs that exit on SIGINT, but 
want to do some cleanup between the signal and the exit, may fail before 
they complete their cleanup".


The following script is of type "wait and unconditional exit", and alows 
ddrescue to terminate before exiting:

#!/bin/bash
interrupted=no
trap 'interrupted=yes' 2
ddrescue -f /dev/zero /dev/null -s 1G
if [ ${interrupted} = yes ] ; then
  echo "ddrescue was terminated by the user" ; exit 130
fi
echo "ddrescue exited normally"


I'll give myself some time to think about the consequences of making 
ddrescue exit by raising SIGINT when the user hits Ctrl-C. Doing this 
would solve this use case, but it may break others.

Feedback is welcome. :-)