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