On 8/12/19, Greg Wooledge <wool...@eeg.ccf.org> wrote:
> On Mon, Aug 12, 2019 at 01:56:46PM -0400, Lee wrote:
>> What's the difference between ${d} and "${d}"? Or is that a bashism
>> also? (all my scripts use /bin/sh so I'm pretty clueless wrt bash)
>
> This applies to both sh and bash.
>
> An unquoted substitution, like $d or ${d}, undergoes several steps. The
> first step is actually copying the contents of the variable. After that
> comes word splitting (dividing the content into words/fields using IFS),
> and then pathname expansion ("globbing").
>
> I have a helper script called "args" which I use to illustrate this stuff.
>
> wooledg:~$ cat bin/args
> #!/bin/sh
> printf "%d args:" "$#"
> printf " <%s>" "$@"
> echo
>
> Using that, we can demonstrate:
>
> wooledg:~$ d="a variable"
> wooledg:~$ args "$d"
> 1 args: <a variable>
> wooledg:~$ args $d
> 2 args: <a> <variable>
>
> The curly braces don't matter in this case, because there's nothing after
> the $d for it to matter.
>
> wooledg:~$ args ${d}
> 2 args: <a> <variable>
>
> The curly braces are only needed because of the _stuff after the d.
> Without them, d_stuff is treated as a variable name.
>
> wooledg:~$ args "$d_stuff"
> 1 args: <>
> wooledg:~$ args "${d}_stuff"
> 1 args: <a variable_stuff>
>
> The quotes are still needed. Without them, we still get word splitting
> and pathname expansion.
>
> wooledg:~$ args ${d}_stuff
> 2 args: <a> <variable_stuff>
>
>
> For more details, see <https://mywiki.wooledge.org/Quotes>.
Wow! It's going to take me a while to understand the implications of
all that, so I'll just stop here with a
Thank you so much for the detailed explanation!
Lee
