Options

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