command cd doesn't work on some builds of zsh

command cd doesn't work on some builds of zsh

[Ajeet D'Souza]

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Hi, I found inconsistent behaviour of the command builtin in some builds on
zsh.

On Fedora 39:
*$ zsh --version*
zsh 5.9 (x86_64-redhat-linux-gnu)
*$ zsh -c 'command cd'*

On Debian 10:
*$ zsh --version*
zsh 5.9 (x86_64-unknown-linux-gnu)
*$ zsh -c 'command cd'*
zsh:1: command not found: cd

According to the manual, command cd should work:

> Run command with args suppressing the normal shell function lookup. *Only
> builtin commands* or commands found in the PATH are executed.


Any idea why different builds on zsh produce different outcomes here?

Thanks,
Ajeet

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Re: command cd doesn't work on some builds of zsh

[Andreas Kähäri]

On Tue, Feb 13, 2024 at 03:24:22PM +0530, Ajeet D'Souza wrote:
> Hi, I found inconsistent behaviour of the command builtin in some builds on
> zsh.
> 
> On Fedora 39:
> *$ zsh --version*
> zsh 5.9 (x86_64-redhat-linux-gnu)
> *$ zsh -c 'command cd'*
> 
> On Debian 10:
> *$ zsh --version*
> zsh 5.9 (x86_64-unknown-linux-gnu)
> *$ zsh -c 'command cd'*
> zsh:1: command not found: cd
> 
> According to the manual, command cd should work:
> 
> > Run command with args suppressing the normal shell function lookup. *Only
> > builtin commands* or commands found in the PATH are executed.
> 
> 
> Any idea why different builds on zsh produce different outcomes here?

Is there in fact an external cd command on the Fedora system?  Is the
POSIX_BUILTINS zsh shell option set by default on the Fedora system?

-- 
Andreas (Kusalananda) Kähäri
Uppsala, Sweden

.

Re: command cd doesn't work on some builds of zsh

[Ajeet D'Souza]

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You're right, Fedora does have a cd binary which is why this works:

*$ which cd*
/usr/bin/cd

However, this still seems like inconsistent behaviour:

*$ /usr/bin/cd "foo"*
# this will not change directories, because a binary cannot change the CWD
of its parent process
*$ command cd "foo"*
# this throws an error on systems without a cd binary, but it actually
calls the shell builtin and changes the CWD

Also, since the manpage mentions that command is supposed to invoke shell
builtins, why does this command fail without POSIX_BUILTINS being set? Is cd
not considered a builtin otherwise?

On Tue, Feb 13, 2024 at 3:35 PM Andreas Kähäri <andreas.kahari@abc.se>
wrote:

> On Tue, Feb 13, 2024 at 03:24:22PM +0530, Ajeet D'Souza wrote:
> > Hi, I found inconsistent behaviour of the command builtin in some builds
> on
> > zsh.
> >
> > On Fedora 39:
> > *$ zsh --version*
> > zsh 5.9 (x86_64-redhat-linux-gnu)
> > *$ zsh -c 'command cd'*
> >
> > On Debian 10:
> > *$ zsh --version*
> > zsh 5.9 (x86_64-unknown-linux-gnu)
> > *$ zsh -c 'command cd'*
> > zsh:1: command not found: cd
> >
> > According to the manual, command cd should work:
> >
> > > Run command with args suppressing the normal shell function lookup.
> *Only
> > > builtin commands* or commands found in the PATH are executed.
> >
> >
> > Any idea why different builds on zsh produce different outcomes here?
>
> Is there in fact an external cd command on the Fedora system?  Is the
> POSIX_BUILTINS zsh shell option set by default on the Fedora system?
>
> --
> Andreas (Kusalananda) Kähäri
> Uppsala, Sweden
>
> .
>

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Re: command cd doesn't work on some builds of zsh

[Peter Stephenson]

On 13/02/2024 11:48 GMT Ajeet D'Souza <98ajeet@gmail.com> wrote:
> Also, since the manpage mentions that command is supposed to invoke
> shell builtins, why does this command fail
> without POSIX_BUILTINS being set? Is cd not considered a builtin
> otherwise?

No, builtins are *only* invoked by "command" when POSIX_BUILTIN is set.
(As I said, native zsh uses "builtin", not "command", for restricting to
builtins.)  The manual page is clear about this:


command [ -pvV ] simple command

The simple command argument is taken as an external command instead of
a function or builtin and is executed. If the POSIX_BUILTINS option  is
set,  builtins  will also be executed but certain special properties of
them are suppressed. The -p flag causes a default path to  be  searched
instead  of  that  in  $path.  With  the -v flag, command is similar to
whence and with -V, it is equivalent to whence -v.


In your case the zsh "builtin" command is more useful, because as you
note you quite definitely don't want to execute the external command
"cd".

pws

Re: command cd doesn't work on some builds of zsh

[Peter Stephenson]

> On 13/02/2024 09:54 GMT Ajeet D'Souza <98ajeet@gmail.com> wrote:
> 
> 
> Hi, I found inconsistent behaviour of the command builtin in some builds on zsh.
> 
> On Fedora 39:
> $ zsh --version
> zsh 5.9 (x86_64-redhat-linux-gnu)
> $ zsh -c 'command cd'
> 
> On Debian 10:
> $ zsh --version
> zsh 5.9 (x86_64-unknown-linux-gnu)
> $ zsh -c 'command cd'
> zsh:1: command not found: cd
> 
> According to the manual, command cd should work:
> > Run command with args suppressing the normal shell function lookup. Only builtin commands or commands found in the PATH are executed.
> 
> Any idea why different builds on zsh produce different outcomes here?

It's likely to be a difference in the setting of the POSIX_BUILTINS
option between the two cases.  By default, with it off, "command"
doesn't apply to builtins --- you'd need to use "builtin cd" in
vanilla zsh to ensure it was running the builtin command.
With POSIX_BUILTINS set it'll find cd.

pws

Re: command cd doesn't work on some builds of zsh

[Lawrence Velázquez]

On Tue, Feb 13, 2024, at 4:54 AM, Ajeet D'Souza wrote:
> According to the manual, command cd should work:
>> Run command with args suppressing the normal shell function lookup. *Only builtin commands* or commands found in the PATH are executed.

This is from the bash man page.

-- 
vq