Re: [bash 4] 'test -v 1' is never true

[Alejandro Colomar]

Hi Branden!

On 11/25/22 22:40, G. Branden Robinson wrote:
> Hi Alex,
>
> At 2022-11-25T22:02:46+0100, Alejandro Colomar wrote:
> > I wrote a script, and am trying it on many systems.  On RHEL8, which
> > has bash 4, it didn't work.  I could reduce the problem to the
> > following command, which never returns true:
> >
> >      test -v 1;
> >
> > In Debian Sid, where I develop, and where I have bash 5, that works
> > fine, and is true if the function or script in which it is has any
> > arguments.  On zsh(1) it also works fine.
> >
> > Is this a known bug in bash?
> > The exact version where I can reproduce it is 4.4.20(1)-release
> > (x86_64-redhat-linux-gnu).
>
> I don't think it is a bug.  It is unspecified behavior according to
> POSIX.
>
> "-v" is not an operator according to POSIX,

Yeah, I know.  I tried dash(1), which at least gives some warning:

    $ cat bug.sh
    #!/bin/bash

    echo $1;

    test -v 1 \
    && echo 'arguments';

    $ dash bug.sh

    bug.sh: 5: test: -v: unexpected operator


> and I don't recall seeing it
> in any shell.  It is therefore interpreted as a string argument.

But `-v` is a specified option of bash(1) (and also, at least, zsh(1)):

    $ help test | grep '\-v'
          -v VAR         True if the shell variable VAR is set.


I find it very useful, since I use `set -Eeufo pipefail` in my scripts, to 
simplify error handling.  When I want to use a variable that might be undefined, 
I first check if it exists.

>    The algorithm for determining the precedence of the operators and the
>    return value that shall be generated is based on the number of
>    arguments presented to test. (However, when using the "[...]" form,
>    the right-bracket final argument shall not be counted in this
>    algorithm.)
>
>    In the following list, $1, $2, $3, and $4 represent the arguments
>    presented to test:
>
>    0 arguments:
>        Exit false (1).
>    1 argument:
>        Exit true (0) if $1 is not null; otherwise, exit false.
>    2 arguments:
>
>            If $1 is '!', exit true if $2 is null, false if $2 is not
>            null.
>
>            If $1 is a unary primary, exit true if the unary test is true,
>            false if the unary test is false.
>
>            Otherwise, produce unspecified results.
>
> https://pubs.opengroup.org/onlinepubs/009695299/utilities/test.html
>
> Regards,
> Branden

Cheers,

Alex

--
<http://www.alejandro-colomar.es/>

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