Where is the Abrowser's bookmarks file?

I believe the file is ~/.mozilla/abrowser/YOUR-PROFILE/bookmarks.html

I suggest you test it by making a new profile (close all abrowser windows and then abrowser -p) then again close all abrowser windows and copy that file from old to the new profile and then go see if that did it.

EDIT: Looks like this source suggests the file you want might be places.sqlite... http://kb.mozillazine.org/Profile_folder_-_Firefox#Files

It seems that it's not easy to use command line to backup bookmarks.

Thank you anyway!

I think bookmarks.html doesn't keep important for my uses data like
tags. It also uses an HTML syntax specific for this use.

~/.mozilla/firefox/PROFILE/places.sqlite keeps bookmarks and history
with all their data. ("PROFILE" is a random-looking name, usually with
.default.) https://developer.mozilla.org/en-US/docs/The_Places_database
documents what it has, it's easy to get some data using SQLite if you
know SQL.

I have a big recfile (https://gnu.org/software/recutils/) with my
bookmarks exported from various browsers (via an ugly script
http://hg.mtjm.eu/forget-scripts/file/tip/forget-import-places.py),
stored in a Mercurial repository. I don't keep the bookmarks in the
browser after an export: it's slower and less convenient than browsing
(without rec-mode yet) the bookmarks recfile in Emacs.