Re: Running commands as "$@"

[alex xmb ratchev]

On Thu, Feb 2, 2023, 5:19 PM Cristian Zoicas <zoicas@medialab.sissa.it>
wrote:

>
>
> Davide Brini wrote:
> > On Thu, 2 Feb 2023 12:11:32 +0100, Cristian Zoicas
> > <zoicas@medialab.sissa.it> wrote:
> >
> >> Now, if a call the script with the commands
> >>
> >>       $ sh runner.sh A=B
> >>
> >> we get the following errors:
> >>
> >>       runner.sh: 10: runner.sh: A=B: not found
> >>
> >> Why the shell does not treat the first string in "$@" ('A=B'
> >> in these cases) as the first possibile token of command (which
> >> is an assignemnt)?
> >
> > It works for me ("sh" points to bash).
> >
> >> In addition, the problem is NOT solved by using 'eval "$@"'.
> >> Apparently it works. For example the command
> >>
> >>        $ sh runner.sh A=BCD
> >>
> >>    works, but
> >>
> >>        $ sh runner.sh A="B    CD"
> >>
> >> gives an error. In this case the error (I think) comes
> >> from the way the expansion of "$@" is performed: eval has to evaluate
> the
> >> string "A=B   CD", so it treats A=B as an assignemnt and 'CD' as
> >> a command.
> >
> > This happens because the quotes are removed by the calling shell before
> eval
> > has a chance to see them. This works:
> >
> > $ sh runner.sh 'A="B    CD"'
> >
> > or even, to check
> >
> > $ sh runner.sh 'A="B    CD"; echo "$A"'
> > B    CD
> >
> >> I am curios what is going on and if there is any possibility of
> >> running a command (any command, including an assignment) by using
> >> a very simple invocation (someting like eval "$@").
> >
> > The short answer is: yes, but not where quoting is involved unless you
> take
> > special measures to ensure that the relevant quotes are seen by eval.
> >
> Correct, but I want to avoid taking these special measures. It is (and it
> was) clear for
> me why the script does not work with eval.
>
> There was a mistake in my original question and I am extremely sorry for
> that.
>
> I wanted to ask the question for this script
>
> # ---- begin script runner.sh ----
> "$@"
> # ---- end script runner.sh ----
>

this runs external cmds only
for bash , eval

>
> and not for the one with "eval"
>
> Here is what I want to obtain:
>
>      A command is a (parsed) sequence of strings and also "$@" is a
> sequence
>      of strings.
>
>      So expected that "$@" would allow me to run anything that was a valid
> command.
>
>      In fact the script above lets me to run "ls -l" but fails to run "A=B"
>
> Hope that clarifies my issue.
>
>
>
>