Re: Why do we need "eval"? (Expect question)

In article <vc0ffk$ml8n$2@dont-email.me>, Rich  <rich@example.invalid> wrote:

Harald Oehlmann <wortkarg3@yahoo.com> wrote:

spawn -noecho printf {\t%s\n} {*}$argv
eventually, this works to:
spawn -noecho printf \t%s\n {*}$argv

>
Do note that the second one causes \t and \n to be interpreted by Tcl's
parser, so printf gets passed a literal tab and literal newline in its
parameter list.  The first passes the \ and t characters on to printf,
and then printf does the interpretation.
>
Both likely work fine for printf, but may not work fine for all
possible external commands.
>

I think you misunderstand Harald's post (i.e., his notation).

The point is that if you pass {{\t%s\n}} to "eval", both sets of braces get
removed and what "printf" sees is (literally)

    backslash tee percent ess backslash en

If you only pass a single level of braces, and eval it, then yes, as you
said, printf will see

    tab percent ess newline

--
"Insisting on perfect safety is for people who don't have the balls to live
in the real world."

    - Mary Shafer, NASA Ames Dryden -