LaTeX definitions for including subfiles (.tex, .bib)

multifile.sty

% multifile.sty
\typeout{A Package for reading subfiles 'multifile' <28 October 2019>}
\ProvidesPackage{multifile}

\usepackage{subfiles}

% a command to run shell commands
% USAGE:
% \app@exe{<command>}
% where:
% - <command> is a shell command to run
%
\makeatletter
\def\app@exe{\immediate\write18}
\makeatother

% a command to include subfiles from a directory.
% USAGE:
% \subfiles{<directory>}
% where:
% - <directory> is a directory with .tex files to include alphabetically
%
\makeatletter
\def\subfiles#1{%
% list the .tex files in the given directory into a temporary build file
  \app@exe{for i in `ls -v #1/*.tex`; do echo "\ subfile{$i}" | tr -d "[:space:]" >> \jobname.subfiles.#1.tmp; done}
% iterate over the filenames in the temporary file and subfile them
  \input{\jobname.subfiles.#1.tmp}
% delete the temporary file
  \AtEndDocument{\app@exe{rm -f \jobname.subfiles.#1.tmp}}
}
\makeatother

% a command to include bibliographies from a directory.
% USAGE:
% \bibliographies{<directory>}
% where:
% - <directory> is a directory with .bib files to include
%
\makeatletter
\def\bibliographies#1{%
% compile all the bibliography files into a single references file
  \app@exe{find #1 -regex ".*bib" | xargs cat | egrep -v "(\%|^$|^\s*$)" > \jobname.references.bib}
% include the compiled bibliography file
  \bibliography{\jobname.references.bib}
}
\makeatother