Finding a file in various locations

Question

I have a central BibTeX file that I have in my home folder. Sometimes, I use it as a git submodule in the subfolder central-bibtex. The relative location can vary a bit. Since I want my preamble to do the work for me, I need it to find it in a couple of possible locations. Those include:

• ../../central-bibtex/Central
• central-bibtex/Central
• ../../zentrale_BibTeX/Central

Once I have a better syntax for this, I would like to add even more:

• ../central-bibtex/Central
• ../zentrale_BibTeX/Central
• ../../../zentrale_BibTeX/Central

So far, I have this, which seems to work:

\IfFileExists{../../central-bibtex/Central}
{\newcommand{\bibliographyfile}{../../central-bibtex/Central}}
{
    \IfFileExists{central-bibtex/Central}
    {\newcommand{\bibliographyfile}{central-bibtex/Central}}
    {\newcommand{\bibliographyfile}{../../zentrale_BibTeX/Central}}
}

Is there some easy way to do this? I am thinking in Python:

dirs = ['../../central-bibtex', 'central-bibtex', '../../zentrale_BibTeX']
for dir in dirs:
    if os.path.isfile(dir + '/Central'):
        bibliographyfile = dir + '/Central'

I have tried TikZ and \foreach, but \bibliographyfile is not set to anything with this:

\newcommand\bibliographyfile{None}

\foreach \path in {
    ../../central-bibtex/Central,
    central-bibtex/Central,
    ../../zentrale_BibTeX/Central,
    /home/mu/Dokumente/Studium/zentrale_BibTeX/Central.bib
}
{
    \AtEndDocument{\path}
    \IfFileExists{\path}
    {\renewcommand\bibliographyfile{\path}}
    {}
}

Answer 1

Since the \foreach loop variable does not surive the loop, you need to expand the value that you are trying to save.. Below I use an \xdef to do that:

Notes:

• I removed the underscores from the paths as that may cause some problems, but there should be solutions on this site that should help.

Code:

\documentclass{article}
\usepackage{tikz}
\newcommand\bibliographyfile{}
\foreach \FileNameWithPath in {
    ../central-bibtex/Central.bib,
    central-bibtex/Central.bib,
    ../../zentrale-BibTeX/Central.bib,
    /home/mu/Dokumente/Studium/zentrale-BibTeX/Central.bib
}{%
    %\AtEndDocument{\path}% <-- not sure what this was for
    \IfFileExists{\FileNameWithPath}{%
        %\xdef\bibliographyfile{\FileNameWithPath}%
        % Per egreg's suggestions, replaced the above with:
        \expandafter\gdef\expandafter\bibliographyfile\expandafter{\FileNameWithPath}
    }{}%
}
\begin{document}
Located file: \bibliographyfile
\end{document}