Extract all citations from .tex file

Question

Is there a fool-proof way to extract all bibtex citation-keys that are cited in a .tex file?

I do not mean regular-expression magic on the .tex-file because this is bound to cause problems when switching between natbib, apacite etc. which all use different citation commands. Also, citations made using \nocite{*} will not be included ...

I though about looking into the .bbl file which does contain all references included in the final document but the format of the .bbl file differs vastly between packages as well such that the key-extraction is difficult.

Answer 1

The citations are contained in the .aux file.

\usepackage{atveryend}
\makeatletter
\let\origcitation\citation
\AtEndDocument{\def\mycites{\@gobble}%
  \def\citation#1{\g@addto@macro\mycites{,#1}\origcitation{#1}}}
\AtVeryEndDocument{\typeout{***^^JCited keys: \mycites^^J***}}
\makeatother

This will show on screen and in the .log file, at the end of the LaTeX run, a message such as

***
Cited keys: xxx,yyy,*
***

It would be possible to avoid the appearance of *, but I don't think it's worthy the trouble. Only actually cited keys will appear (BibTeX uses \citation{*} as a signal for including the whole database).

One can output the citations to an auxiliary file, instead:

\makeatletter
\let\origcitation\citation
\AtEndDocument{\def\mycites{}%
  \def\citation#1{\g@addto@macro\mycites{#1^^J}\origcitation{#1}}}
\AtVeryEndDocument{\newwrite\citeout\immediate\openout\citeout=\jobname.cit
  \immediate\write\citeout{\mycites}\immediate\closeout\citeout}
\makeatother

Then, if the file is test.tex, the citation keys will be saved in the file test.cit one per line.

Answer 2

With bibtool you can do as follows:

bibtool -- preserve.key.case=on -x file.aux -o bibliography.bib

This extracts your cited bibliography. Now if you just grep the file for lines with @ in them, you get fairly close to a list of keys. The option preserve.key.case=on ensures that the case of the keys is not altered (in response to the comment below).

Answer 3

Various TeX-aware programming editors have macros to achieve this. For instance, there's a package called bibmacros for use with winedt which (inter alia) does the job you describe. It works on the .aux file created by latex and BibTeX, and creates a new bib file called jobname-minimal.bib, where jobbame is the name of the aux file (without the "aux" extension, of course). Other editors must have similar macros, either built-in or accessible as extra packages.