Even if I use Calc more often than Gnumeric (and actually I tried to spend as less time as possible on spreadsheet programs), the latter provides a tool I’m fond of, ssconvert:

ssconvert - a command line spreadsheet format converter

It offers a very efficient way to convert .xlsx into .csv, for instance:

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mkdir csvFiles
ssconvert -S spreadsheet.xlsx csvFiles/%s.csv

I the command lines above, I first create the folder ‘csvFiles’ with mkdir and then I use ssconvert with option -S that stands for --export-file-per-sheet:

Export a file for each sheet if the exporter only supports one sheet at a time. The output filename is treated as a template in which sheet number is substituted for %n and/or sheet name is substituted for %s. If there are not substitutions, a default of “.%s” is added. (see man ssconvert)

So, basically, assuming there are two sheets ‘sheet1’ and ‘sheet2’ in my file spreadsheet.xlsx, then I’ll get sheet1.csv and sheet2.csv in my folder ‘csvFiles’ 🎆.

I find ssconvert extremely helpful in my workflow as several colleagues of mine work with spreadsheet programs as a database management software 😐: I use ssconvert as the first step of my analysis pipeline so that I never modify the original database and use a format easy to manipulate with the programming languages I use 😏.