Convert excel spreadsheet to csv on linux (xlsx to csv)

Get gnumeric

apt-get install gnumeric

Then use ssconvert to do the conversion

ssconvert oldfile.xlsx newfile.csv

On a headless server (such as a droplet) it may issue a lot of warnings. Pipe output and warning to null via:

ssconvert oldfile.xlsx newfile.csv > /dev/null 2>&1

Well this is a nifty trick!

Source