I have a book collection which I would to have an index of. Fortunately, most recent books have a barcode on their cover which indicates their ISBN, an identifier which is unique for the book and can be used (at least in theory) to retrieve details about the book (title, author, cover image sometimes...). Thus, to keep a list of what is in my bookshelves, I just have to scan the barcode of each book and save the list somewhere.
To do this, I need a tool which takes a video stream as input and outputs the list of recognized EAN-13 codes, one per line. I do not need a fancy app with a slick captive user interface which would try to be smart and store a database in some mysterious place while making it harder for me to script things. Do one thing, and do it well.
If someone else intends to do this, here are two possible ways, and ideas to use the ISBNs.
Barcode Scanner on Android
This is actually a pretty natural thing to do with an Android phone, except you have to find the right barcode scanning app. (Most turn out to be riddled with ads, or ridiculous limitations, or don't have the required feature.)
The ZXing library has an Android port called Barcode Scanner which was able to read almost all tested barcodes with the webcam of my HTC Desire. Activate the Bulk scan mode option in Settings, scan items, go to History, select Send history (beware, Clear history is right next to it and has no confirmation step), and send an email to yourself with the csv attachment. It is free as in freedom (Apache License 2.0).
The zbarcam command (packaged for Debian) is exactly what I needed, but my computer's webcam was too crappy to scan barcodes. This might work for you if you have a better webcam. For the record, before learning about Barcode Scanner, I tried to use my HTC Desire as a webcam over USB using AndroidUsbCamera. Sadly, it does not work on recent kernels because it requires V4L1 support which was dropped in kernel 2.6.38.
What to do with the ISBNs
I thought that an ISBN lookup program would be packaged for Debian, but apparently not. The simplest API to use seems to be that of Open Library (a nice project, by the way, which provides dumps which are apparently in the public domain): example for ISBN 9780517223628. 56 out of my 115 scanned books were found.
For better options, a good starting point seems to be this StackOverflow thread. It seems that the Google Books API is the best one, but interfacing with Google APIs seems to require API keys, registration, etc., so I didn't bother yet.