Re: [bug #65981] "bash test -v" does not work as documented with "export KEY="

[Andreas Kähäri]

On Fri, Jul 12, 2024 at 10:15:02PM -0400, anonymous wrote:
> URL:
>   <https://savannah.gnu.org/bugs/?65981>
> 
>                  Summary: "bash test -v" does not work as documented with
> "export KEY="
>                    Group: The GNU Bourne-Again SHell
>                Submitter: None
>                Submitted: Sat 13 Jul 2024 02:15:01 AM UTC
>                 Category: None
>                 Severity: 3 - Normal
>               Item Group: None
>                   Status: None
>                  Privacy: Public
>              Assigned to: None
>              Open/Closed: Open
>          Discussion Lock: Any
> 
> 
>     _______________________________________________________
> 
> Follow-up Comments:
> 
> 
> -------------------------------------------------------
> Date: Sat 13 Jul 2024 02:15:01 AM UTC By: Anonymous
> The documentation of the
> [https://www.gnu.org/software/bash/manual/bash.html#Bash-Conditional-Expressions
> Bash-Conditional-Expressions] "-v varname" says:
> 
> > -v varname
> >    True if the shell variable varname is set (has been assigned a value).
> 
> I think "export TEST_EQUAL_WITHOUT_VALUE=" does not assign a value to the
> varname, does it?


After the "export", the variable has been *set*. The statement
also assigns an empty string to the variable, so it has a value (testing
the variable's value against an empty string would yield a boolean true
result, showing that there is a value to test with).

The "export" is unimportant, it just promotes the shell variable to an
environment variable, which isn't relevant to this issue.
  
If you want to test whether a variable contains only an empty string,
use "test -z variablename". Note that that does not test whether the
variable is *set* though (unset variables expand to empty strings too,
unless "set -u" is in effect, in which case it provokes an "unbound
variable" diagnostic from the shell).

Andreas


> Test case:
> > docker run -it --rm bash:latest
> > export TEST_EQUAL_WITHOUT_VALUE=
> > if test -v TEST_EQUAL_WITHOUT_VALUE; then echo "true"; else echo "false";
> fi
> 
> The output is "true", but there is no value assigned to it.
> 
> That is fine to me. I suggest to change the documentation and remove the "(has
> been assigned a value)" part.
> 
> 
> Tested with: GNU bash, version 5.2.26(1)-release (x86_64-pc-linux-musl)
> 
> 
> 
> 
> 
> 
> 
>     _______________________________________________________
> 
> Reply to this item at:
> 
>   <https://savannah.gnu.org/bugs/?65981>
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-- 
Andreas (Kusalananda) Kähäri
Uppsala, Sweden

.