When printing info from the files not using “-l” argument, a much longer length comes out than if use the “-l” option. Is it possible to print out the entire database with the full-length field?
Not that I’m aware of.
Do you know why is if the file is printed it comes out a longer number than if the database is printed?
Good question! The long answer is that the beets database tracks the metadata about your files at the time they were imported. If the files change after that point, then the beets database won’t know. The simplest explanation is that the files themselves have been changed or replaced.
The beet update command updates the database according to the current state of the files.
It also occurs to me that you could use find to make info give you data for all files. For example, something like find . -iname '*.mp3' -exec beet info {} + might work (but I haven’t tried it).