Relative paths for \input and building from different directories

Question

The minimal example

If I have a directory containing my main LaTeX source file and it uses \input to incorporate some data in another file, I can use a relative pathname. E.g., with these files:

~/tmp/relative-paths-mwe/mwe.tex

\documentclass{article}
\begin{document}
\input{./src/ex.tex}
\end{document}

~/tmp/relative-paths-mwe/src/ex.tex

some input

Now, from the command line, if I'm in ~/tmp/relative-paths-mwe, I can build as expected:

~/tmp/relative-paths-mwe$ pdflatex mwe.tex 
This is pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013)
...
Output written on mwe.pdf (1 page, 12192 bytes).
Transcript written on mwe.log.

However, if I'm in the parent directory, ~/tmp/, I can't build because the relative paths (as I understand it, and based on the symptoms) are resolved with respect to the current working directory rather than the file where the \input appears:

~/tmp$ pdflatex relative-paths-mwe/mwe.tex 
...! LaTeX Error: File `./src/ex.tex' not found.

Type X to quit or <RETURN> to proceed,
or enter new name. (Default extension: tex)

Enter file name: 

Is there a way to specify the paths in such a way that I can refer to other content using relative paths, but still be able to call pdflatex from arbitrary directories?

The non-minimal example

I think that the above is a complete minimal working example for which if I get an answer, I can solve my actual problem. In case there's a difference that someone can predict in advance, or anyone is wondering why I'm trying to do something unusual, a bit of explanation is in order. I've got a source repository for a project, and it has a subdirectory for a LaTeX document, and a subdirectory for an Apache Maven project. The document had been using the listings environment to include source code from the Maven project using relative paths along the lines of

../mavenproject/src/more-path/code.extension

There's a LaTeX Maven Mojo that's supposed to be able to compile LaTeX documents, so I decided to try moving the document directory to mavenproject/src/latex/mydoc. Now, I can build the document manually from mavenproject/src/latex/mydoc if I change the relative paths to

../../more-path/code.extension

but I can't build with those paths using the LaTeX Mojo, because it's run from the mavenproject directory, which is several directories up from the document root. I can obviously adjust to handle that, but then I can't build from mydoc anymore. I'm hoping that there's a way to specify the pathnames relative to the including document, or to specify the a document root, and write paths relative to that. I hope that a solution to the minimal example above will transfer over to my actual situation.

Answer 1

Rather than

\input{./src/ex.tex}

It'd usually better to do

\input{ex.tex}

then use (from anywhere)

TEXINPUTS=$HOME/tmp/relative-paths-mwe//:$TEXINPUTS: pdflatex mwe

It isn't really that relative paths are resolved against the current working directory but rather they are resolved against the directories in TEXINPUTS (whether specified as an environment variable or a kpathsea configuration in texmf.cnf file. By ending the path with // you allow subdirectories to be searched so the ex.tex will be found in the src subdirectory, as well as the mwe.tex from the commandline. the trailing : in TEXINPUTS ensures that the standard places are also searched for the usual classes and packages.

Answer 2

Alternative:

\documentclass{article}
\usepackage[abspath]{currfile}  % ← need this package
\begin{document}
\input{\currfileabsdir/src/ex.tex}  % use `\currfileabsdir`
\end{document}

How it work should be very obvious. As noted in the currfile package documentation you need -recorder flag, and you might want to experiment with \InputIfFileExists etc. if you use MikTeX (for details why refer to the documentation of that package...)