How do I know which Metadata Source Plugin was called from fetch-ebook-metadata?

[eryMpexI]

Hello everybody,
I'm running fetch-ebook-metadata from Shell:

fetch-ebook-metadata --isbn="${ISBN}" --opf 2>/dev/null

Occasionally, the script fails with this error:

-:26.1: Extra content at the end of the document
Failed to get cached URL from google for URL: https://www.amazon.com/Norton-Read

I don't know which metadata plugin throws this error.

The forum says:

You can obtain the plugin error details by starting Calibre in debug mode

But I'm not starting the whole Calibre app, just fetch-ebook-metadata.

What's the best approach to troubleshoot this?

Ideally, I would configure the Shell script to restrict the run to one plugin each time using --allowed-plugin, see what result I get, and only use a different source if the request fails, but it's not something I can code right now.
So, I wonder how to know this

[kovidgoyal]

Use the --verbose option and examine the log

[eryMpexI]

Originally Posted by kovidgoyal

Use the --verbose option and examine the log

Thanks.
Follow up question:

Is there a way to silence errors and get only the metadata?
The utility outputs failures like so, until it finds a valid source:

Failed to get cached URL from google for URL: https://www.amazon.com/Peyote-Mescaline-Drugs-Straight-Facts/dp/0791085457 with error: HTTP Error 429: Too Many Requests
Failed to get cached URL from google for URL: https://www.amazon.com/Essential-Homer-Hackett-Classics/dp/0872205401 with error: HTTP Error 429: Too Many Requests
Failed to get cached URL from google for URL: https://www.amazon.com/Norton-Anthology-American-Literature-8th/dp/0393918858 with error: HTTP Error 429: Too Many Requests
Title : Peyote and Mescaline
Author(s) : M. Foster Olive
....

Is there a way to tell the utility to not print stderr?

Thank you

[kovidgoyal]

redirect stderr to /dev/null

[eryMpexI]

Originally Posted by kovidgoyal

redirect stderr to /dev/null

I have.
It doesn't work, you can see in my original message:

2>/dev/null

So, this stream is written to stdout, not sterr:

Failed to get cached URL from google for URL:

That's why I asked

[kovidgoyal]

| grep -v '^Failed'

[eryMpexI]

Originally Posted by kovidgoyal

| grep -v '^Failed'

Thanks, I ended up doing something similar (in Shell), using awk to match only the XML:

fetch-ebook-metadata --isbn="${ISBN}" --opf | awk '/<?xml/,/package>/'