As a reminder to myself, because I will do this once in a blue moon and won’t remember. If I need to manipulate an animated gif image on linux, Gifsicle is a useful tool.

On Ubuntu, install with

sudo apt install gifsicle

The two operations that I used

Cut frames from the end of the gif:

1. Get info

gifsicle --info gif_file

Which will display the image number #0 - #n

2. Specify the start and end frames. Below shows start at the first image and run to the nth image (100 in this case). Output the file to new_gif_file

gifsicle gif_file "#0-100" > new_gif_file

Resize:

1. Resize the image to width 800px and maintain aspect ratio (_ will calculate the appropriate height to use to maintain aspect ratio), -o is the output filename

gifsicle gif_file --resize 800x_ -o new_gif_file

Further details on the Gifsicle website and useful information at the askubuntu forums which is where I found out about this tool.