The S Series will only log commands that create configuration changes..
The two commands you are looking for to enable the most verbose logging of command line actions on the S and K series are (this assumes you already have a syslog destination configured);
set logging application CLI level 8
set logging application Security level 8
The 'Security' application will log when (and which) users log in and out. The 'CLI' application will log what commands are entered that are configuration changes.
Logging ALL cli commands would need to be a feature request.
Best Regards,
Larry