Filter Streams Converter only logs in UI

When converting a Confluence export with the Filter Streams Converter the only log available is the one produced on the fly in the UI during the conversion.
They are difficult to retrieve, they have to be copied by hand by selecting the first line and pressing simultaneously left-shift and fast-arrow-down until the end of the log from its window is reached, at each time a space is being converted.
A more automated way is desirable.
The XML logs produced are more complicated to work with, and they vanish each time a new conversion is performed.
What we need to be able to work with logs in a workable manner is conventional logs day by day no matter how many spaces are converted during a day, and stored in /var/log/xwiki as regular text files, such as conversion-day-time.log or so (the xwiki subdirectory exists).
So it would be nice if the logs from the web backend could be piped to such text logs each time a space has been converted to XWiki.