zsh precommand modifiers stop accepting argument if quoted

zsh precommand modifiers stop accepting argument if quoted

[Cuong Manh Le]

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Hi,

I see this behavior of `exec` and `command` precommand modifiers:

$ zsh -c '\exec -a foo zsh -c "print -- \$0"'
zsh:1: command not found: -a
$ zsh -c '\command -v ls'
zsh:1: command not found: -v

Sounds like they stopped accepting its options if quoted.

Is this behavior a feature or a bug? it it documented somewhere?

The full context: http://unix.stackexchange.com/q/354586/38906

Thanks.

Cuong Manh Le
https://cuonglm.xyz

Re: zsh precommand modifiers stop accepting argument if quoted

[Bart Schaefer]

On Wed, Mar 29, 2017 at 11:00 PM, Cuong Manh Le
<cuong.manhle.vn@gmail.com> wrote:
>
> $ zsh -c '\exec -a foo zsh -c "print -- \$0"'
> zsh:1: command not found: -a
> $ zsh -c '\command -v ls'
> zsh:1: command not found: -v
>
> Is this behavior a feature or a bug? it it documented somewhere?

There's no promise that precommand modifiers will work at all when
quoted. They're syntactic tokens, so if you quote them they become
different tokens. It just happens that "exec" and "command" are both
implemented as builtins, so the quoted forms can still be looked up
and run that way, but if you have changed the token then the
corresponding syntax rules do not apply.

This is similar to the way that "typeset" as a reserved word differs
from "typeset" as a builtin command.  The typeset dichotomy was
introduced a lot more recently and so is more carefully documented --
there's probably a doc clarification that could be made for the
precommand modifiers.

Re: zsh precommand modifiers stop accepting argument if quoted

[Cuong Manh Le]

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So there no way to prevent an alias named "command" to expand without
breaking the script? In other Bourne-like shell, once can do:

\builtin command -v ls


but it's just broken in zsh. It doesn't work even in sh, ksh emulation, so
making zsh non-compliant there.

>From user perspective, it's definitely a bug.

Cuong Manh Le
https://cuonglm.xyz

On Fri, Mar 31, 2017 at 5:42 AM, Bart Schaefer <schaefer@brasslantern.com>
wrote:

> On Wed, Mar 29, 2017 at 11:00 PM, Cuong Manh Le
> <cuong.manhle.vn@gmail.com> wrote:
> >
> > $ zsh -c '\exec -a foo zsh -c "print -- \$0"'
> > zsh:1: command not found: -a
> > $ zsh -c '\command -v ls'
> > zsh:1: command not found: -v
> >
> > Is this behavior a feature or a bug? it it documented somewhere?
>
> There's no promise that precommand modifiers will work at all when
> quoted. They're syntactic tokens, so if you quote them they become
> different tokens. It just happens that "exec" and "command" are both
> implemented as builtins, so the quoted forms can still be looked up
> and run that way, but if you have changed the token then the
> corresponding syntax rules do not apply.
>
> This is similar to the way that "typeset" as a reserved word differs
> from "typeset" as a builtin command.  The typeset dichotomy was
> introduced a lot more recently and so is more carefully documented --
> there's probably a doc clarification that could be made for the
> precommand modifiers.
>