convert excel to csv command line linux

$ ssconvert Book1.xlsx newfile.csv
Using exporter Gnumeric_stf:stf_csv

$ cat newfile.csv 
Foo,Bar,Baz
1,2,3
123.6,7.89,
2012/05/14,,
The,last,Line
libreoffice --headless --convert-to csv $filename --outdir $outdir