How do I use the unload command to export a table to a IXF file
Ah ok.

If you are referring to the UNLOAD command, that is only available on DB2 for z/OS. DB2 LUW does not have an UNLOAD command....except if you purchase IBM's separate product Optim High Performance Unload. (I am assuming you are wishing to use that?)

Optim High Performance Unload uses the db2hpu command. And though we do not use the tool where I work, it appears that the syntax you are after is the following:

db2hpu -t 'S.T' -d &lt;database-name&gt; -format ixf -m 'filesystem/messages.MSGS' -o 'filesystem/myfile.IXF'