I've got a file with some book data in MARC format, of which some lines are ISBNs. I'd like to replace these lines with the Google Books ID of that ISBN, if it exists. Here's the code so far, which just ends up removing the lines:
perl -pe "s#ISBN(.*)#$(wget --output-document=- --quiet --user-agent=Mozilla/5.0 \"http://books.google.com/books?jscmd=viewapi&bibkeys=\1\")#mg" < 5-${file} > 6-${file}
PS: Google are a bit fuzzy on the use of automated tools: The Books Data API recommends tools like curl / wget, but there are no instructions on how to avoid being blocked when using such tools. I'm also pretty sure I saw a clause in a ToS saying users can't send automated queries, but I can't find it again. This is discussed in their forum.