Some \glspl{command} may have one or more \glspl*{optional}. Unlike
\glspl{mandatory}, optional arguments must always be enclosed in
square brackets \gls{opt.opensq}~\gls{opt.closesq}.
\xminisec{Example:}
The command \gls{newline.dbbackslashchar} ends a line.
So the following segment of code:
\begin{codeS}
Line one\glsni{newline.dbbackslashchar}Line two.
\end{codeS}%
will produce the following output:
\begin{result}[Line one <newline> Line two]\setlength{\parindent}{1.5em}%
Line one\\Line two.
\end{result}%
However the \glsni{newline.dbbackslashchar} command also
has an optional
argument that allows you to specify how big the gap between the two
lines should be. So the following segment of code:
\begin{codeS}
Line one\glsni{newline.dbbackslashchar}\oarg{1cm}Line two.
\end{codeS}%
will produce the following output:
\begin{result}[Line one <1cm vertical gap> Line two]\setlength{\parindent}{1.5em}%
Line one\\[1cm]Line two.
\end{result}
Incidentally, note the
difference between the previous example, and the following example:
\begin{codeS}
Line one\glsni{newline.dbbackslashchar}\marg{[1cm]} Line two.
\end{codeS}\screenpagebreak
\begin{result}[newlineargs.html]\setlength{\parindent}{1.5em}%
Line one\\{[1cm]} Line two.
\end{result}%
\faq{Start of line goes awry}{newlineargs}In this example the \texttt{[1cm]} has been placed inside a group, so
it is no longer considered to be an optional argument, and since the
command \glsni{newline.dbbackslashchar} does not take a
mandatory argument,
the \texttt{[1cm]} is simply interpreted as ordinary text.

\xminisec{Example:}
The command \glsi{framebox} (which will be covered later in
\sectionref{sec:fbox}) takes a
\gls{mandatory} and two optional arguments.
\glsni{framebox} puts a frame around the contents of its
mandatory argument:
\begin{codeS}
\glsni{framebox}\marg{Some Text}
\end{codeS}%
\begin{resultS}[Image of the words 'Some Text' inside a rectangular
box where there is a narrow gap between the edge of the text and the
frame]
\framebox{Some Text}
\end{resultS}
The first optional argument can be used to make the box a specified
width:
\begin{codeS}
\glsni{framebox}\oarg{4cm}\marg{Some Text}
\end{codeS}%
\begin{resultS}[Image of the words 'Some Text' centred inside a
rectangular box of width 4cm (plus a narrow gap)]
\framebox[4cm]{Some Text}
\end{resultS}
The second optional argument specifies the
justification of the text (\underline{l}eft, \underline{r}ight or
\underline{c}entred) within the box:
\begin{codeS}
\glsni{framebox}\oarg{4cm}\oarg{r}\marg{Some Text}
\end{codeS}%
\begin{resultS}[Image of the words 'Some Text' right justified inside a
rectangular box of width 4cm (plus a narrow gap)]
\framebox[4cm][r]{Some Text}
\end{resultS}
\glspar
In general, if a command has both optional and mandatory arguments,
the optional arguments are usually specified first (although there
are a few exceptions).