Are you using Heroku and want to run a program not included in the Heroku environment? I’m going to show you how.

For Speaker Deck we wanted to be able to extract the text from uploaded pdf’s so that we can index them and make them searchable, but the program we’d been using to do this on our dev machines, pdftotext (part of the XPDF library), wasn’t available on our Heroku instances.

On a whim I typed “heroku run bash” and sure enough I was dropped into a bash shell with our Heroku Cedar Stack instance.

heroku run bash

Then I went into our apps tmp directory and tried a wget with the xpdf url, but it failed so I tried curl with the -o option to output to file and it worked. Then I unzipped the file and started building it!

curl -o xpdf.tar.gz
tar zxvf xpdf.tar.gz
cd xpdf-3.02

When it was done building I found the executable we needed, pdftotext, sitting in the xpdf build directory. I scp’d it to my machine, created a bin directory in our apps folder, and stuck the executable there. Then with a quick git commit and git push to Heroku we were in business!

If I had an environment locally that was identical to the Heroku instance I could have built it locally, but to ensure it was built to run on the Heroku instance it just made sense to build it there in the first place.

The bin directory was added to the apps path automatically so I was able to execute the pdftotext program from inside our Rails app without a hitch.

Update: Josh Peek commented on the Hacker News post that he bundled the xpdf source in a gem which compiles itself at runtime… Probably a better longterm solution as it works if the underlying environment changes enough to break a prebuilt binary.