[lug] What the heck can I use ${VAR:-} for?

[Jeffrey Haemer]

Sean,

[Sound of hand smacking forehead.]
Of course!  Thanks.  Cool new trick internalized.

On Wed, Apr 16, 2008 at 11:31 AM, Sean Reifschneider <jafo at tummy.com> wrote:

> Jeffrey Haemer wrote:
> >    if [ "${BOOTUP:-}" != "verbose" ]; then
> >
> > What's this mean?  Specifically, why's it different from this?
> >
> >    if [ "$BOOTUP" != "verbose" ]; then
>
> There is a mode you can run the shell in, which is off by default, in
> which
> referencing an unset variable is an error.  The default is that accessing
> an unset variable results in an empty string.  So, if this mode is set,
> doing:
>
>   [ "$BOOTUP" != verbose ] && echo true
>
> will result in an error.  Where:
>
>   [ "${BOOTUP:-}" != verbose ] && echo true
>
> will not.
>
> Sean
> --
> Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
> tummy.com, ltd. - Linux Consulting since 1995: Ask me about High
> Availability
>
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-- 
Jeffrey Haemer <jeffrey.haemer at gmail.com>
720-837-8908 [cell]
http://goyishekop.blogspot.com
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