Comment out sections of text in bib file

Question

What's the correct way to comment out sections of explanatory text (included for humans to read) in a .bib file? I would like biber/biblatex to simply ignore this text.

When I put in text like

#######################################################################
## PREPRINTS

I get warnings like

WARN - BibTeX subsystem: /tmp/8XsEEmjVOo/bib-latest.bib_14175.utf8, line 7, warning: 139 characters of junk seen at toplevel

Answer 1

Anything that is not inside a recognized entry is a comment. So just type along! Any .bib interpreter that complains about it is buggy, as it is not following the rules laid down in btxdoc. However, you can use an entry like @COMMENT, which will hopefully not trigger any complains.

Answer 2

At least with biber, you should be able to use the same commenting method as with LaTeX, that is using % for the commented line.

After a few test comments can be outside entries, within entries (commenting a whole line) or commenting the end of a line.

%%%%%%%%%%%
% PREPRINT
@article{myarticle,
    author = {Onymous, A. N.}, %The author
    % the title of the article
    title = {A Nice title},
}

Should work as expected. However this may not be the case with bibtex.

Answer 3

I had difficulties commenting out entries in a .bib file (as opposed to adding free-standing comments). Posts to date on this thread did not address this particular problem.

I'm using Overleaf). What I observed:

• bibtex looks for entries (@blah) before it checks if the line starts with a % (or so I figured).
• but only that line gets processed; if you commented out the entire entry the rest of it (title=, etc) is ignored and you end up with errors ('missing field') attributable to @blah

Sheesh.

This doesn't work:

%@article{foo2019,
% ...
% }

This works (replace the @):

%%article{foo2019,
% ...
% }

I poked around in Overleaf and found this explanation (note that mine, above, is a bit different):

% is actually not a comment character in .bib files! So, inserting a % in .bib files not only fails to comment out the line, it also causes some BibTEX errors. To get BibTEX to ignore a particular field we just need to rename the field to something that BibTEX doesn’t recognise. For example, if you want to keep a date field around but prefer that it’s ignored (perhaps because you want BibTEX to use the year field instead) write Tdate = {...} or the more human-readable IGNOREdate = {...}.

To get BibTEX to ignore an entire entry you can remove the @ before the entry type. A valid reference entry always starts with a @ followed by the entry type; without the @ character BibTEX skips the lines until it encounters another @.

bibtex is very focused on @; biber apparently respects %s (but you'd have to use biblatex). See pointers provided by moewe (in the comments) for other discussion.