Convert .xls and .xlsx files to csv using Apache POI.
This is a simple wrapper around the example implementations of both .xls and .xlsx parsing with a few fixes for handling of odd strings put in. The original source is here:
As it stands, it will take multiple sheets and append them to the same file, making what's technically an invalid file.
Also, the packaging process will include all of the POI schemas, so tends to end up far larger than you'd expect.
It uses scala's SBT build system, which you can install from their download page. Once that's done, run
sbt one-jar
Then copy the file from target/scala-2.9.1/xlsx2csv_2.9.1-0.1.0-one-jar.jar to somewhere in your path.
java -jar xls2csv.jar /path/to/xls-or-xlsx /path/to/csv-output