oarsinsync is correct. The standard on most UNIX-like OSes is that long options, e.g. --long, have two dashes, and short options, e.g. -l, have one. It allows

oarsinsync is correct. The standard on most UNIX-like OSes is that long options, e.g. --long, have two dashes, and short options, e.g. -l, have one. It allows you to combine multiple options into one. For example, the following two commands are equivalent: $ ls -laF $ ls -l -a -F