Re: sed syntex in procmailrc question

Bart Schaefer <[email protected]> writes:

> To expand just a little on Harry's correct explanation:
>
> In the literal example you included, the single quotes around
> 's/SUBJET/' are unnecessary.  You only need quotes to protect spaces,
> dollar signs, and globbing characters like *?[].
>
> However, my guess is that your real sed expression, which you have not
> shown us, doesn't have the string SUBJET but instead has a complex
> string that might contain some of those special characters that need
> quoting.
>
> In that case for clarity I might have written such an expression as
>
> sed -e s/'The Real String Goes Here'/"$SUBJ"/g
>
> rather than butting the two sets of quotes up against each other.

Again no expert here but let me move off sed for a moment since I'm
more familiar with awk.  Aren't there cases with awk where spaces are
not the issue but allowing a shell Variable to expand are what
matters?

For example if you have a variable say, in the environment.  And you
want it to expand inside some awk code in .procmailrc.   Wouldn't you
need to do something like awk '/somestring/{print $0"'$MY_ENV_VAR'"}'

Where in effect you are stopping the awk code to allow the expansion
and then taking it up again.

I realize there are other constructs that would serve the same purpose
and avoid quoting quagmires like:

  awk -v var=$MY_ENV_VAR '{print var}'

But I'm just thinking there are usages where single quotes are used
for something besides spaces.