
The default behavior for a command may usually be modified by adding --option to the command. For example, the ls command has an -s option. The ls -s will include file sizes in the listing. There is also a -h option to display file sizes in a “human readable” format.
Options can be grouped in clusters, so
ls -sh
is the same command as
ls -s -h
Most options have a long version prefixed with two dashes instead of one, so
ls --size --human-readable
is the same command as
ls -sh