Re: How to test if a variable is declared?

[Andreas Kusalananda Kähäri]

On Fri, Mar 13, 2020 at 06:15:16AM -0500, Peng Yu wrote:
> This involves printing something to the screen. Is there something along
> the line of [[ that doesn’t print to screen? Thanks.

if declare -p foo 2>/dev/null; then
   # foo is declared
else
   # foo is not declared
fi



> 
> On Thu, Mar 12, 2020 at 10:07 PM David <address@hidden> wrote:
> 
> > On Fri, 13 Mar 2020 at 13:59, Peng Yu <address@hidden> wrote:
> >
> > > What is the best way
> > > to test whether a viable is declared?
> >
> > Here's one way:
> >
> > $ echo "$BASH_VERSION"
> > 4.4.12(1)-release
> > $ unset v
> > $ declare -p v ; echo $?
> > bash: declare: v: not found
> > 1
> > $ declare v
> > $ declare -p v ; echo $?
> > declare -- v
> > 0
> > $
> >
> > --
> Regards,
> Peng

-- 
Andreas (Kusalananda) Kähäri
SciLifeLab, NBIS, ICM
Uppsala University, Sweden

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