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\documentclass[12pt,a4paper]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{tgpagella}
\usepackage[margin=1in]{geometry}
\usepackage[svgnames]{xcolor}
\usepackage[colorlinks, linkcolor={blue}, urlcolor={blue}]{hyperref}
\usepackage[breakable]{tcolorbox}
\tcbuselibrary{listings}
\newcommand{\checkcites}{\texttt{checkcites}}
\newcommand{\email}[1]{\small\texttt{#1}}
\newcommand{\version}{Version 2.8 from December 14, 2024.}
\newenvironment{infoblock}[1]
{\par\addvspace{\medskipamount}
\begin{tcolorbox}[colframe=DarkTurquoise,coltitle=black,fonttitle=\bfseries,title=#1]}
{\end{tcolorbox}\addvspace{\medskipamount}}
\newenvironment{terminal}
{\par\addvspace{\medskipamount}
\begin{tcolorbox}[colframe=DarkTurquoise]}
{\end{tcolorbox}\par\addvspace{\medskipamount}}
\title{The \checkcites\footnote{\version}\ \ script}
\author{%
Enrico Gregorio\\\email{Enrico.Gregorio@univr.it}\\[3ex]
Island of \TeX\\\email{https://gitlab.com/islandoftex}%
}
\date{}
\begin{document}
\maketitle
\tableofcontents
\section{Introduction}
\label{sec:intro}
\checkcites\ is a Lua script written for the sole purpose of
detecting unused or undefined references from both \LaTeX\ auxiliary
or bibliography files. We use the term \emph{unused reference} to
refer to the reference present the bibliography file~--~with the
\verb|.bib| extension~--~but not cited in the \verb|.tex| file.
The term \emph{undefined reference} is exactly the opposite, i.e,
the item cited in the \verb|.tex| file, but not present in the
\verb|.bib| file.
The original idea came from a question posted
in the \TeX\ community at Stack Exchange about
\href{http://tex.stackexchange.com/questions/43276}{how to check
which bibliography entries were not used}. We decided to write a
script to check references. We opted for Lua, since it is a very
straightforward language and it has an interpreter available on every
modern \TeX\ distribution.
\begin{infoblock}{Attention!}
From version 2.1 on, \checkcites\ relies on specific libraries
available in the \verb|texlua| ecosystem and thus is not be supported
in vanilla \verb|lua| interpreters. Please make sure to use this
script with an updated \verb|texlua| interpreter in order to ensure
the correct behaviour.
\end{infoblock}
\section{How the script works}
\label{sec:howto}
\checkcites\ uses the generated auxiliary files to start the
analysis. From version 2.0 on, the scripts supports two backends:
\begin{description}
\item[\texttt{bibtex}] Default behavior, the script checks
\verb|.aux| files looking for citations, in the form of
\verb|\citation{a}|. For every \verb|\citation| line found,
\checkcites\ will extract the citations and add them to a
table, even for multiple citations separated by commas, like
\verb|\citation{a,b,c}|. The citation table contains no duplicate
values. At the same time \checkcites\ also looks for bibliography
data, in the form of \verb|\bibdata{a}|. Similarly, for every
\verb|\bibdata| line found, the script will extract the bibliography
data and add them to a table, even if they are separated by commas,
like \verb|\bibdata{d,e,f}|. Again, no duplicate values are allowed.
Stick with this backend if you are using Bib\TeX\ or Bib\LaTeX\ with
the \verb|backend=bibtex| package option.
\item[\texttt{biber}] With this backend, the script checks
\verb|.bcf| files (which are XML-based) looking for citations, in the
form of \verb|bcf:citekey| tags. For every tag found, \checkcites\
will extract the corresponding values and add them to a table. The
citation table contains no duplicate values. At the same time
\checkcites\ also looks for bibliography data, in the form of
\verb|bcf:datasource| tags. Similarly, for every tag found, the
script will extract the bibliography data and add them to a table.
Again, no duplicate values are allowed. Stick with this backend if
you are using Bib\LaTeX\ with the default options or with the
\verb|backend=biber| option explicitly set. It is important to note,
however, that the \verb|glob=true| option is not supported yet.
\end{description}
\begin{infoblock}{Attention!}
If \verb|\citation{*}| (Bib\TeX) or simply \verb|*| (Bib\LaTeX)
is found, \checkcites\ will issue a message telling that
\verb|\nocite{*}| is in the \verb|.tex| document, but the script will
do the check nonetheless.
\end{infoblock}
Now, \checkcites\ will extract all entries from the bibliography
files found in the previous steps, regardless of which backend was
used. For every element in the bibliography data table, the script
will look for entries like \verb|@BOOK|, \verb|@ARTICLE| and so
forth~--~we actually use pattern matching for this~-- and add their
identifiers to a table. No duplicate values are allowed.
\begin{infoblock}{Attention!}
If \checkcites\ cannot find a certain bibliography file, the script
ends. Make sure to put the correct name of the bibliography file in
your \verb|.tex| file.
\end{infoblock}
Let there be $A$ and $B$ the sets of citations and references,
respectively. In order to get all unused references in the
\verb|.bib| files, we compute the set difference:
\[
B - A = \{ x : x \in B, x \notin A \}.
\]
Similarly, in order to get all undefined references in the
\verb|.tex| file, we compute the set difference:
\[
A - B = \{ x : x \in A, x \notin B \}.
\]
If there are either unused or undefined references, \checkcites\ will
print them in a list format. In Section~\ref{sec:usage} there is a
more complete explanation on how to use the script.
\section{Usage}
\label{sec:usage}
\checkcites\ is very easy to use. First of all, let us define two
files that will be used here to explain the script usage. Here is our
sample bibliography file \verb|example.bib|, with five fictional
entries.
\begin{tcblisting}{colframe=DarkTurquoise,coltitle=black,listing only,
title=Bibliography file, fonttitle=\bfseries, breakable,
listing options={columns=fullflexible,basicstyle=\ttfamily}}
@BOOK{foo:2012a,
title = {My Title One},
publisher = {My Publisher One},
year = {2012},
editor = {My Editor One},
author = {Author One}
}
@BOOK{foo:2012b,
title = {My Title Two},
publisher = {My Publisher Two},
year = {2012},
editor = {My Editor Two},
author = {Author Two}
}
@BOOK{foo:2012c,
title = {My Title Three},
publisher = {My Publisher Three},
year = {2012},
editor = {My Editor Three},
author = {Author Three}
}
@BOOK{foo:2012d,
title = {My Title Four},
publisher = {My Publisher Four},
year = {2012},
editor = {My Editor Four},
author = {Author Four}
}
@BOOK{foo:2012e,
title = {My Title Five},
publisher = {My Publisher Five},
year = {2012},
editor = {My Editor Five},
author = {Author Five}
}
\end{tcblisting}
The second file is our main \LaTeX{} document, \verb|document.tex|.
Observe that we will stick with Bib\TeX\ for now and check Bib\LaTeX\
later on.
\begin{tcblisting}{colframe=DarkTurquoise,coltitle=black,listing only,
title=Main document, fonttitle=\bfseries,
listing options={columns=fullflexible,basicstyle=\ttfamily}}
\documentclass{article}
\begin{document}
Hello world \cite{foo:2012a,foo:2012c},
how are you \cite{foo:2012f},
and goodbye \cite{foo:2012d,foo:2012a}.
\bibliographystyle{plain}
\bibliography{example}
\end{document}
\end{tcblisting}
Open a terminal and run \verb|checkcites|:
\begin{terminal}
\begin{verbatim}
$ checkcites
\end{verbatim}
\tcblower\small
\begin{verbatim}
_ _ _ _
___| |_ ___ ___| |_ ___|_| |_ ___ ___
| _| | -_| _| '_| _| | _| -_|_ -|
|___|_|_|___|___|_,_|___|_|_| |___|___|
checkcites.lua -- a reference checker script (v2.8)
Copyright (c) 2012, 2019, Enrico Gregorio, Paulo Cereda
Copyright (c) 2024, Enrico Gregorio, Island of TeX
--------------------------------------------------------------------------
I am sorry, but you have not provided any command line argument, including
files to check and options. Make sure to invoke the script with the actual
arguments. Refer to the user documentation if you are unsure of how this
tool works. The script will end now.
\end{verbatim}
\end{terminal}
If you do not have \checkcites\ installed with your \TeX\
distribution, you can run the standalone script \verb|checkcites.lua|
with either \verb|texlua| or \verb|lua|. We recommend to use
\verb|texlua|, as it is shipped with all the modern \TeX\
distributions:
\begin{terminal}
\begin{verbatim}
$ texlua checkcites.lua
\end{verbatim}
\end{terminal}
When you run \checkcites\ without providing any argument to it, the a
message error will appear. Do not panic! Try again with the
\verb|--help| flag:
\begin{terminal}
\begin{verbatim}
$ checkcites --help
\end{verbatim}
\tcblower\small
\begin{verbatim}
_ _ _ _
___| |_ ___ ___| |_ ___|_| |_ ___ ___
| _| | -_| _| '_| _| | _| -_|_ -|
|___|_|_|___|___|_,_|___|_|_| |___|___|
checkcites.lua -- a reference checker script (v2.8)
Copyright (c) 2012, 2019, Enrico Gregorio, Paulo Cereda
Copyright (c) 2024, Enrico Gregorio, Island of TeX
Usage: checkcites.lua [ [ --all | --unused | --undefined ] [ --backend
<arg> ] <file> [ <file 2> ... <file n> ] | --help | --version ]
-a,--all list all unused and undefined references
-u,--unused list only unused references in your bibliography files
-U,--undefined list only undefined references in your TeX source file
-c,--crossrefs enable cross-reference checks (disabled by default)
-b,--backend <arg> set the backend-based file lookup policy
-j,--json <file> export the generated report as a JSON file
-h,--help print the help message
-v,--version print the script version
Unless specified, the script lists all unused and undefined references by
default. Also, the default backend is set to "bibtex". Please refer to the
user documentation for more details.
\end{verbatim}
\end{terminal}
Since we are using Bib\TeX, we do not need to set up the
backend! Simply provide the auxiliary file~--~the one with the
\verb|.aux| extension~--~which is generated when you compile your
main \verb|.tex| file. For example, if your main document is named
\verb|foo.tex|, you probably have a \verb|foo.aux| file too. Let us
compile our sample document \verb|document.tex|:
\begin{terminal}
\begin{verbatim}
$ pdflatex document.tex
\end{verbatim}
\end{terminal}
After running \verb|pdflatex| on our \verb|.tex| file, there is now a
\verb|document.aux| file in our work directory.
\begin{tcblisting}{colframe=DarkTurquoise,coltitle=black,listing only,
title=Auxiliary file, fonttitle=\bfseries,
listing options={columns=fullflexible,basicstyle=\ttfamily}}
\relax
\citation{foo:2012a}
\citation{foo:2012c}
\citation{foo:2012f}
\citation{foo:2012d}
\citation{foo:2012a}
\bibstyle{plain}
\bibdata{example}
\end{tcblisting}
Now we can run \checkcites\ on the \verb|document.aux| file:
\begin{terminal}
\begin{verbatim}
$ checkcites document.aux
\end{verbatim}
\tcblower\small
\begin{verbatim}
_ _ _ _
___| |_ ___ ___| |_ ___|_| |_ ___ ___
| _| | -_| _| '_| _| | _| -_|_ -|
|___|_|_|___|___|_,_|___|_|_| |___|___|
checkcites.lua -- a reference checker script (v2.8)
Copyright (c) 2012, 2019, Enrico Gregorio, Paulo Cereda
Copyright (c) 2024, Enrico Gregorio, Island of TeX
Great, I found 4 citations in 1 file. I also found 1 bibliography file. Let
me check this file and extract the references. Please wait a moment.
Fantastic, I found 5 references in 1 bibliography file. Please wait a
moment while the reports are generated.
--------------------------------------------------------------------------
Report of unused references in your TeX document (that is, references
present in bibliography files, but not cited in the TeX source file)
--------------------------------------------------------------------------
Unused references in your TeX document: 2
=> foo:2012b
=> foo:2012e
--------------------------------------------------------------------------
Report of undefined references in your TeX document (that is, references
cited in the TeX source file, but not present in the bibliography files)
--------------------------------------------------------------------------
Undefined references in your TeX document: 1
=> foo:2012f
\end{verbatim}
\end{terminal}
As we can see in the script output, \checkcites\ analyzed
both \verb|.aux| and \verb|.bib| files and managed to find two
unused references in the bibliography file~--~\verb|foo:2012b|
and \verb|foo:2012e|~--~and one undefined reference in the
document~--~\verb|foo:2012f|.
\checkcites\ allows a couple of command line flags that will tell it
how to behave. For example, check this command line:
\begin{terminal}
\begin{verbatim}
$ checkcites --unused document.aux
\end{verbatim}
\end{terminal}
The \verb|--unused| flag will make the script only look for unused
references in the \verb|.bib| file. The argument order does not
matter, you can also run:
\begin{terminal}
\begin{verbatim}
$ checkcites document.aux --unused
\end{verbatim}
\end{terminal}
The script will behave the same. Similarly, you can use:
\begin{terminal}
\begin{verbatim}
$ checkcites --undefined document.aux
\end{verbatim}
\end{terminal}
The \verb|--undefined| flag will make the script only look
for undefined references in the \verb|.tex| file. If you want
\checkcites\ to look for both unused and undefined references, run:
\begin{terminal}
\begin{verbatim}
$ checkcites --all document.aux
\end{verbatim}
\end{terminal}
If no special argument is provided, the \verb|--all| flag is set as
default.
Observe that our example relied on the default backend, which
uses Bib\TeX. Let us change our document a bit to make it
Bib\LaTeX-compliant:
\begin{tcblisting}{colframe=DarkTurquoise,coltitle=black,listing only,
title=Main document, fonttitle=\bfseries,
listing options={columns=fullflexible,basicstyle=\ttfamily}}
\documentclass{article}
\usepackage{biblatex}
\addbibresource{example.bib}
\begin{document}
Hello world \cite{foo:2012a,foo:2012c},
how are you \cite{foo:2012f},
and goodbye \cite{foo:2012d,foo:2012a}.
\printbibliography
\end{document}
\end{tcblisting}
As usual, let's compile our sample document \verb|document.tex|:
\begin{terminal}
\begin{verbatim}
$ pdflatex document.tex
\end{verbatim}
\end{terminal}
After running \verb|pdflatex| on our \verb|.tex| file, there is now a
\verb|document.aux| file in our work directory, as expected. However,
since we are using Bib\LaTeX\ as well, there is another file of
interest in our working directory, one that has a \verb|.bcf|
extension! In order to run \checkcites\ on that specific file, we
need to provide the \verb|biber| backend:
\begin{terminal}
\begin{verbatim}
$ checkcites --backend biber document.bcf
\end{verbatim}
\end{terminal}
We can even omit the file extension, the script will automatically
assign one based on the current backend:
\begin{terminal}
\begin{verbatim}
$ checkcites --backend biber document
\end{verbatim}
\end{terminal}
Now, let us run \checkcites\ on the \verb|.bcf| file, providing the
\verb|biber| backend:
\begin{terminal}
\begin{verbatim}
$ checkcites --backend biber document.bcf
\end{verbatim}
\tcblower\small
\begin{verbatim}
_ _ _ _
___| |_ ___ ___| |_ ___|_| |_ ___ ___
| _| | -_| _| '_| _| | _| -_|_ -|
|___|_|_|___|___|_,_|___|_|_| |___|___|
checkcites.lua -- a reference checker script (v2.8)
Copyright (c) 2012, 2019, Enrico Gregorio, Paulo Cereda
Copyright (c) 2024, Enrico Gregorio, Island of TeX
Great, I found 4 citations in 1 file. I also found 1 bibliography file. Let
me check this file and extract the references. Please wait a moment.
Fantastic, I found 5 references in 1 bibliography file. Please wait a
moment while the reports are generated.
--------------------------------------------------------------------------
Report of unused references in your TeX document (that is, references
present in bibliography files, but not cited in the TeX source file)
--------------------------------------------------------------------------
Unused references in your TeX document: 2
=> foo:2012b
=> foo:2012e
--------------------------------------------------------------------------
Report of undefined references in your TeX document (that is, references
cited in the TeX source file, but not present in the bibliography files)
--------------------------------------------------------------------------
Undefined references in your TeX document: 1
=> foo:2012f
\end{verbatim}
\end{terminal}
If you rely on cross-references in your bibliography file,
\checkcites\ might complain about unused entries. We can try the
experimental feature available from version 2.3 on that attempts to
check cross-references through the \verb|--crossrefs| command line
flag:
\begin{terminal}
\begin{verbatim}
$ checkcites --crossrefs document.aux
\end{verbatim}
\end{terminal}
This feature is disabled by default and it is known to work with both
\verb|bibtex| and \verb|biber| backends. Please report if you find an
issue.
From version 2.7 on, \checkcites\ can export the reference report to a
JSON file through the \verb|--json| command line flag:
\begin{terminal}
\begin{verbatim}
$ checkcites document.aux --json report.json
\end{verbatim}
\end{terminal}
The script will generate a file named \verb|report.json| with the
following structure and content:
\begin{tcblisting}{colframe=DarkTurquoise,coltitle=black,listing only,
title=JSON file, fonttitle=\bfseries, breakable,
listing options={columns=fullflexible,basicstyle=\ttfamily}}
{
"settings" : {
"backend" : "bibtex",
"operation" : "list all unused and undefined references",
"crossrefs" : false
},
"project" : {
"forcibly_cite_all" : false,
"bibliographies" : [ "example" ],
"citations" : [ "foo:2012a", "foo:2012c",
"foo:2012f", "foo:2012d" ],
"crossrefs" : []
},
"results" : {
"unused" : {
"active" : true,
"occurrences" : [ "foo:2012b", "foo:2012e" ]
},
"undefined" : {
"active" : true,
"occurrences" : [ "foo:2012f" ]
}
}
}
\end{tcblisting}
Note that the JSON file has three main groups. The first
group contains the execution settings and has the backend used,
a description of the operation being performed, and whether
cross-references checks were enabled. The second group contains
relevant information about the project itself, such as whether all
references will be cited (when \verb|\nocite{*}| is found), and the
list of bibliographies, citations and cross-references found. Finally,
the third group contains the analysis results, with a special
\verb|active| key that indicates whether that particular check has
been performed, and a list of occurrences. That is all, folks!
\section{License}
\label{sec:license}
This script is licensed under the
\href{http://www.latex-project.org/lppl/}{\LaTeX\ Project Public
License}. If you want to support \LaTeX{} development by a
donation, the best way to do this is donating to the
\href{http://www.tug.org/}{TeX Users Group}.
\end{document}