Need to remove borders from multiple images

Need to remove borders from multiple images

I have a few hundred family images and they were all sent to us with borders that I would like to remove. Thankfully the borders are all the same size of 20 pixels and they are all .jpg so this will probably make things easier but im looking for a way to "batch process" all of them quickly so I dont need to open photoshop for each image and do it individually. Command line is preferred, the only big problem is they are mostly different sizes.