Re: sed with Variable Substitution in the command

[alex xmb sw ratchev]

sorry .. where is $11 and error ?

On Thursday, September 26, 2024, Wiley Young <wyeth2485@gmail.com> wrote:

> From: Steve Matzura
>   "... Variable substitution has always been a problem for me because there
> doesn't seem to be a single hard-and-fast rule--sometimes the variable is
> quoted, sometimes it's wrapped in braces...."
>
>
> Regarding braces, it's always permissible to surround a parameter name in
> braces, meaning that adding braces won't cause an error. On the other hand,
> there are numerous situations where omitting braces would cause an error.
>
> Okay         ??
> ====     ====
> "${foo}"
>             "$foo" is okay
> "${bar##_*}"
>             "$bar##_*" is an error
> "${1}"
>             "$1" is okay
> "${11}"
>             "$11" is an error
> "${array[1]}"
>              "$array[1]" is an error
>
> I use the term "error" loosely to mean, unintended effects will occur.
>
> Braces are also used for other things as well: compound commands, function
> definitions, and brace expansion among others. Each of these are something
> else, though.
>
> Just always using braces _is_ extra typing. Some might say that it's less
> _readable._ Still, doing so lets users more errors while remembering fewer
> rules.
>
> Wiley
>