Most options also have a short option name. Short options start with
a single dash, and are followed by a single character, e.g., -t
(which is equivalent to --list). The forms are absolutely
identical in function; they are interchangeable.
The short option names are faster to type than long option names.
Short options which require arguments take their arguments immediately
following the option, usually separated by white space. It is also
possible to stick the argument right after the short option name, using
no intervening space. For example, you might write -f archive.tar or -farchive.tar instead of using
--file=archive.tar. Both --file=archive-name and
-f archive-name denote the option which indicates a
specific archive, here named archive.tar.
Short options which take optional arguments take their arguments
immediately following the option letter, without any intervening
white space characters.
Short options' letters may be clumped together, but you are not
required to do this (as compared to old options; see below). When
short options are clumped as a set, use one (single) dash for them
all, e.g., ‘tar -cvf’. Only the last option in
such a set is allowed to have an argument1.
When the options are separated, the argument for each option which requires
an argument directly follows that option, as is usual for Unix programs.
$ tar -c -v -b 20 -f /dev/rmt0
If you reorder short options' locations, be sure to move any arguments
that belong to them. If you do not move the arguments properly, you may
end up overwriting files.
 Clustering many
options, the last of which has an argument, is a rather opaque way to
write options. Some wonder if GNU getopt should not
even be made helpful enough for considering such usages as invalid.
Published under the terms of the GNU General Public License