Re: [Libguestfs] Shebang sh plugins (was: Re: [PATCH nbdkit v2 03/10] python: Implement nbdkit API version 2.)

On Fri, Nov 22, 2019 at 11:07 PM Richard W.M. Jones <rjones(a)redhat.com&gt; wrote: > > On Fri, Nov 22, 2019 at 02:55:31PM -0600, Eric Blake wrote: > > Unrelated side topic: in your recent addition of eval.sh, you > > wondered if we should promote it to a full-blown plugin rather than > > just an example script. But reading 'man nbdkit-sh-plugin', there > > is no mention of turning an executable script into a full-blown > > plugin via a shebang, the way that python documents it. [I guess > > 'man nbdkit' sort of mentions it under Shebang scripts] > > I believe it's not possible to do it for sh plugins. > > For (eg) python plugins it works like this: > > #!/usr/sbin/nbdkit python > -> runs nbdkit python <script name> > -> <script name> is interpreted as magic script= parameter > -> the python plugin works by loading the script using > PyRun_SimpleFileEx which interprets the contents of the > script as python code > > However for shell it doesn't work: > > #!/usr/sbin/nbdkit sh > -> runs nbdkit sh <script name> > -> <script name> is interpreted as magic script= parameter > -> the sh plugin works by actually executing the script > -> executing the script repeats the steps over from the top, > causing an infinite loop > > If you can think of a way to make this work it would be a useful > feature IMO. Even if we can find a way, it sounds too complicated, and I don't see the use case.