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PDFDetach

This repository downloads the binaries, e.g. pdfdetach and publish them back as i.e. a ruby-gem — suitable for Ubuntu 16.04, 18.04 and 20.04.

How it works?

On the target system: overloading the LD_LIBRARY_PATH variable allows to execute arbitrary binaries, abusing of that we can ship those and their required .so files within a tarfile.

  • First we setup a docker image with an particular Ubuntu version:
    • install the binary of our interest, then we use docker cp to get a copy
    • retrieve the used .so files the binary uses with ldd, also we get a copy of them
  • Now we have the binaries, they are copied inside our bin directory:
    • they are released using git worktree — it turns out you can use directories as branches, like for gh-pages we're using it for pushing final files only
    • they are ignored by default on the main repository — but a .gitignore is placed inside this new branch with bin/* to sill ignore all binaries and, i.e. !bin/20.04 to actually skip the desired version of binaries
  • The ruby-gem is written as usual but the version.rb gets rewritten on release time to match the target environment, a LIB_TARGET constant is set as i.e. 20.04 (or 18.04, etc.)
    • you don't need to modify this file, the make release task will setup that for you — also you can set MAJOR and PATCH for specific version values, the MINOR will be 20, 18 or 16 according the target runtime, e.g. make release TAG=v16 PATCH=2 MAJOR=1 will be 1.16.2
    • probably you can use something else, not just ruby — try hacking the Makefile to match another stack, just keep in mind the bin folder should remain inside the created directory!

Makefile can be configured to fetch another binaries, see the PKG, DEPS and ARGS variables — see how dependencies are fetched on the install.sh script.

Integration tests

If you're on a system with Docker running:

  • type make to setup all docker images required
  • type make test to run the available tests on each of them

Try make dev to spawn a Bash session: once inside Ubuntu, type make check

Publishing modules

We're using Ruby as the target language, see the pdfdetach/lib/pdfdetach/main.rb file to see how the wrapper works.

The make release task will care about the versioning bits, it will commit on a separated branch each release with their respective binaries also commited.

To release a particular version try make release TAG=v16

Using this module

Include it in your Gemfile, make sure to set the version to the Ubuntu release you'll be using it on.

# For Ubuntu 20.04
gem 'pdfdetach', '0.20.1'

Licensing

This gem is available as open source under the terms of the GNU General Public License

Poppler is licensed under the GNU General Public License v2