You can just use the "alternate value" parameter expansion rule:
$ export DEBUG=
$ export DISPLAY=foo.bar.com:0.0
$ echo ${DEBUG:+$DISPLAY}
$ export DEBUG=1
$ echo ${DEBUG:+$DISPLAY}
foo.bar.com:0.0
$
Maarten Broekman
> -----Original Message-----
> From: redhat-list-bounces@xxxxxxxxxx
> [mailto:redhat-list-bounces@xxxxxxxxxx] On Behalf Of ESGLinux
> Sent: Monday, May 04, 2009 7:41 AM
> To: General Red Hat Linux discussion list
> Subject: Re: bash debug tips. semi OT
>
> First tip for my question
>
> reference:
> http://www.softpanorama.org/Scripting/Shellorama/bash_debugging.shtml
>
> ### debecho (debug-echo), by Stefano Falsetto ###
> ### Will echo passed parameters only if DEBUG is set to a value. ###
> debecho () {
> if [ ! -z "$DEBUG" ]; then
> echo "$1" >&2
> # ^^^ to stderr
> fi
> }
>
> DEBUG=on
> Whatever=whatnot
> debecho $Whatever # whatnot
>
> DEBUG=
> Whatever=notwhat
> debecho $Whatever # (Will not echo.)
>
>
> something better??? ;-)
>
> ESG
>
>
> 2009/5/4 ESGLinux <esggrupos@xxxxxxxxx>
>
> > Hello all
> >
> > this is a question about debuging bash scripts. I think
> this is a semi off
> > topic because its not a red hat question ... but I´m sure
> all of us have an
> > answer to this question.
> >
> > I have several scripts with echo commands to check variable values
> >
> > the code I use is like this
> >
> > if [ ! -z $DEBUG ]; then
> > echo "variable: $variable"
> > fi
> >
> > thus If I set DEBUG=on I get a lot messages with the
> variable values.
> >
> > My question is if is there any tip to do this without
> using the if code
> > snipet (something like an inline function...)
> >
> > on the other hand any tip about debugging bash scripts is
> welcome (like
> > setting option flags -n, -v o -x)
> >
> > Greetings
> >
> > ESG
> >
> >
> >
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