Firstly install jpegoptim.
You can do this on Debian like systems using apt:
sudo apt-get update && sudo apt-get install jpegoptim
Then go to directory with jpeg files and use this command:
find . -name '*.jpg' -exec jpegoptim -m70 -o -f --strip-all {} \;
It will find all jpg files recursively and optimize with following settings:
- m70 stands for jpeg quality (about 70 – 80 should be fine but lossy)
- o is for overwrite
- f is for force
- strip-all removes all EXIF and other textual data from files