Re: [tlug] Rsync exclusion question

[John Fremlin <john@example.com>]

Josh Glover wrote:
> I think the Best Practise to always use non-interpolating quotes 
> unless you know you need interpolation is the way to go. That way,
> you don't need to understand the interpolation rules of your
> programming language all the way down to the metal.

I don't know how you can include not understanding the language you are 
using in a Best Practice ;-)

Seeing as the interpolation and wildcard expansion rules affect both the
security and correctness of your scripts, spending a few minutes to
understand these simple rules will not only save you time debugging (for
certain) but also possibly prevent minor catastrophes. (Both over- and
under- quoting cause problems.)

I don't understand why the problem was allegedly fixed by changing 
between " and ' quotes; perhaps we haven't heard the full story.

From the Bash manpage
>        Enclosing  characters  in  double quotes preserves the literal value of
>        all characters within the quotes, with the exception of $, ‘,  \,  and,
>        when  history  expansion  is enabled, !.  The characters $ and ‘ retain
>        their special meaning within double quotes.  The backslash retains  its
>        special  meaning only when followed by one of the following characters:
>        $, ‘, ", \, or <newline>.  A double quote may be quoted  within  double
>        quotes by preceding it with a backslash.  If enabled, history expansion
>        will be performed unless an !  appearing in double  quotes  is  escaped
>        using a backslash.  The backslash preceding the !  is not removed.
>
>        The  special  parameters  *  and  @ have special meaning when in double
>        quotes (see PARAMETERS below).


From the BSD sh manpage
>    Single Quotes
>      Enclosing characters in single quotes preserves the literal meaning of
>      all the characters (except single quotes, making it impossible to put
>      single-quotes in a single-quoted string).
>
>    Double Quotes
>      Enclosing characters within double quotes preserves the literal meaning
>      of all characters except dollarsign ($), backquote (‘), and backslash
>      (\).  The backslash inside double quotes is historically weird, and
>      serves to quote only the following characters:
>            $ ‘ " \ <newline>.
>      Otherwise it remains literal.