Re: Irregularities when using -v, -z, -n

[Alex fxmbsw7 Ratchev]

use aliases or eval, and proper var assignments

On Thu, Jul 29, 2021, 15:12 <eduardo-chibas@caramail.com> wrote:

> How can I print if some condition is true or false?
>
> Have tried but failed using
>
>   local aa
>
>   echo "local aa"
>   p=[[ -v aa ]] ; q=[[ ! -v aa ]]
>   echo "[[ -v aa ]] $p [[ ! -v aa ]] $q"
>   [[ -v aa ]] && echo "[[ -v aa ]]: Variable exists."
>   [[ ! -v aa ]] && echo "[[ ! -v aa ]]: Variable unknown."
>
>
>
> > Sent: Friday, July 30, 2021 at 1:04 AM
> > From: eduardo-chibas@caramail.com
> > To: leonid.isaev@ifax.com
> > Cc: help-bash@gnu.org
> > Subject: Irregularities when using -v, -z, -n
> >
> > How does manual never give examples of how to use things !
> >
> > 6.4 Bash Conditional Expressions
> >
> > Everyone is expected to figure things out by themselves.
> >
> >
> >
> > > Sent: Friday, July 30, 2021 at 12:34 AM
> > > From: "Leonid Isaev (ifax)" <leonid.isaev@ifax.com>
> > > To: help-bash@gnu.org
> > > Subject: Re: Irregularities when using -v, -z, -n
> > >
> > > On Thu, Jul 29, 2021 at 10:27:08AM +0200, eduardo-chibas@caramail.com
> wrote:
> > > > I am getting confused with the following code
> > >
> > > Well, perhaps you could read "help test"? If you did, you'd see:
> > > -----8<-----
> > > ...
> > >    String operators:
> > >       -z STRING      True if string is empty.
> > >       -n STRING      True if string is not empty.
> > > ...
> > >       -v VAR         True if the shell variable VAR is set.
> > >       -R VAR         True if the shell variable VAR is set and is a
> name
> > >                      reference.
> > > ...
> > > ----->8-----
> > >
> > > Therefore,
> > >
> > > >   [[ -v aa ]] && echo "[[ -v aa ]]: Variable exists."
> > >
> > > tests if a variable is set, but
> > >
> > > >   [[ -z aa ]] && echo "[[ -z aa ]]: Variable exists, size is zero."
> > >
> > > tests that a string "aa" is zero length. You need to replace aa ->
> "$aa" here.
> > > Also, [[ -z ... ]] returns 0 also for unset variables.
> > >
> > > --
> > > Leonid Isaev
> > >
> > >
> >
> >
>
>