Replace \input{fileX} by the content of fileX automatically

You can use the following tools to do this. All of them are on CTAN but not all of them are part of either TeXLive or MikTeX, so you may need to manually install them. They need either Perl or a C compiler installed. Both should not be a problem with Linux but might be one under Windows or Mac. However IIRC TeXLive installs its own Perl interpreter.

---

latexpand Perl script:

Latexpand is a Perl script that simply replaces \input and \include commands with the content of the file input/included. The script does not deal with \includeonly commands.

Installation:

Simply download it from http://mirrors.ctan.org/support/latexpand/latexpand and run it. You need Perl installed however.

Usage:

    perl latexpand mainfile.tex > newfile.tex

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flatex

A C program to flatten a LaTeX file into a single file, by explicitly including the files included by \include and \input commands. Also, if BibTeX is being used, then includes the bbl file into the resulting file. The result is therefore a stand-alone LaTeX file that can be emailed to a collaborator.

Installation:

Get the single C file and compile it, e.g. with cc flatex.c -o flatex.

Usage:

    flatex mainfile.tex > newfile.tex

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flatten

A program to flatten a LaTeX root file by copying \input and \include files into the root file.

Installation:

Get the ZIP file from CTAN, unpack it and run make followed by make install. You need a C compiler and maybe flex for this. However it seems quite old and you might run in trouble because of it. I failed compiling it!

Usage:

    flatten mainfile.tex newfile.tex

You need an installed Perl. Save it as buildFile.pl and make it executable or run it with perl buildFile.pl

eval '(exit $?0)' && eval 'exec perl -S $0 ${1+"$@"}' && eval 'exec perl -S $0 $argv:q'
  if 0;
#use strict;
# 
# Usage:
# buildFile.pl < main-file.tex > main-file.tot
#     
sub p_inc {
  $DateiName = shift;
    if ( open (my $datei, "$DateiName.tex") ) {
      print "%%%---------- open: ", $DateiName, "\n";
      while (<$datei>) {
        if (/^\s*\\include{\s+(\S+)/i) {
          my $include = $1;
          chomp($include);chop($include);
          print "%%%%%%%%% Springe nach ", $include, "\n";
          p_inc($include);
        } else { print unless /^\s*(#|$)/; }
      }
      print "%%%---------- close: ", $DateiName, "\n";
      close $datei;
    } else { print "%%%<===== Datei existiert nicht\n"; }
}
#
@zeilen = (<>);
for $zeile (@zeilen) {
  next if $zeile =~ /^\s*(%)/;
  if ($zeile =~ /^\s*\\include{\s*(\S+)/i) {
    my $include = $1;
    chomp($include);
    chop($include);
    print "%%%%%%%%%%% Springe nach ", $include, "\n";
    p_inc($include);
  } else { print $zeile; }

I tried all the options mentioned in this post, but the original flatex works best for me. There appears to be a newer version, but I was unable to compile it as I am not familiar with multi-file C sources. If anyone could try it and let me know about the outcome that would be great.

The original flatex has an issue as it only creates a .flt (the flattened document), even when you specify a different .tex as the output. But that's not really an issue. I have created a batch file that sorts that out and allows integration with Subversion as well (see this post on my website http://www.jwe.cc/2012/02/workflow-with-subversion-and-latex/).