This gist shows how to create a GIF screencast using only free OS X tools: QuickTime, ffmpeg, and gifsicle.
To capture the video (filesize: 19MB), using the free "QuickTime Player" application:
Note: these instructions are for pre-Sierra MacOS. Sierra (10.12) and newer users see https://gist.github.com/gravitylow/fb595186ce6068537a6e9da6d8b5b96d by @gravitylow
If you are getting this in gdb on OSX while trying to run a program: