GNU/Linux Command-Line Conventions

• The arguments that programs expect fall into two categories: options (or flags) and other arguments. Options modify how the program behaves, while other arguments provide inputs (for instance, the names of input files).
• the command ls -s / displays the contents of the root directory.
• The $-$size option is synonymous with -s, so the same command could have been invoked as ls $-$size /.