Re: Question about Ctrl-C and less

On 2005-10-19, Kevin Brown <kevin(at)sysexperts(dot)com> wrote:
> Making assumptions about what the pager will do upon receipt of SIGINT
> is folly as well.
>
> Setting up SIGINT to be ignored may be the right answer (I don't
> believe it is -- see below), but if so then it needs to be done
> properly. If it gets ignored prior to the popen(), then the child
> will also end up ignoring it by default, because signal disposition is
> inherited by child processes. If we ignore SIGINT, it should be after
> the popen(), not before.

I do not believe it is possible to do the signal disposition correctly
and still use popen() to run the pager. (You would need to reimplement
popen using raw syscalls.)

> So I think the right answer here is for psql to handle SIGINT
> internally by doing a pclose() first

The chances that psql can do this safely approach zero. pclose() is not a
signal-safe function, so it can only be called from a signal handler if
you _know_ that the signal did not interrupt any non-signal-safe function.
(Nor can the signal handler longjmp out in such a case, unless the code is
never again going to call any unsafe function.)

--
Andrew, Supernews
http://www.supernews.com - individual and corporate NNTP services