Skip rendered frames
SkipRenderedFrames This script renders the current scene, from start frame to end frame, skipping images that already exist in the rendering path. (Works with the extensions specified here below. If you render to files with some other extension, you must add it manually to the list.
The most useful use (yes...) of this script is when you leave a rendering task unattended, typically a week-end giant-animation-rendering. You make a command-line rendering using the script (in a shellscript, a .bat file, whatever) You configure your OS to start the job again in case of problem, power shortage, etc... (At or Cron in linux, Scheduled Tasks in Windows), and the rendering job will resume, skipping everything that got rendered already.