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Irregularities when using -v, -z, -n
From: |
eduardo-chibas |
Subject: |
Irregularities when using -v, -z, -n |
Date: |
Thu, 29 Jul 2021 15:11:58 +0200 |
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
> >
> >
>
>
- Irregularities when using -v, -z, -n, eduardo-chibas, 2021/07/29
- Re: Irregularities when using -v, -z, -n, Leonid Isaev (ifax), 2021/07/29
- Irregularities when using -v, -z, -n, eduardo-chibas, 2021/07/29
- Irregularities when using -v, -z, -n,
eduardo-chibas <=
- Re: Irregularities when using -v, -z, -n, Alex fxmbsw7 Ratchev, 2021/07/29
- Re: Irregularities when using -v, -z, -n, Alex fxmbsw7 Ratchev, 2021/07/29
- Re: Irregularities when using -v, -z, -n, Leonid Isaev (ifax), 2021/07/29
- Irregularities when using -v, -z, -n, eduardo-chibas, 2021/07/29
- Re: Irregularities when using -v, -z, -n, Leonid Isaev (ifax), 2021/07/29
- Irregularities when using -v, -z, -n, eduardo-chibas, 2021/07/29
- Irregularities when using -v, -z, -n, eduardo-chibas, 2021/07/29
- Re: Irregularities when using -v, -z, -n, Leonid Isaev (ifax), 2021/07/29
- Re: Irregularities when using -v, -z, -n, Greg Wooledge, 2021/07/29
- Irregularities when using -v, -z, -n, eduardo-chibas, 2021/07/29