http://www.purinchu.net/wp/2005/06/11/advanced-parameter-substitution-with-bash/ The answer to life, the universe, and everything Fri, 10 Feb 2012 03:15:56 +0000 hourly 1 http://wordpress.org/?v=3.3.1 http://www.purinchu.net/wp/2005/06/11/advanced-parameter-substitution-with-bash/comment-page-1/#comment-6574 felipe1982 Wed, 13 Apr 2011 03:14:16 +0000 http://www.purinchu.net/wp/2005/06/11/advanced-parameter-substitution-with-bash/#comment-6574 > First off, let me demonstrate with a sample: > > KDEDOCS=${KDEDOCS:-default} > > The :- says that if KDEDOCS is unset (or is set to a null value), > then to use default as the result. The original variable is left > unchanged. Unfortunately, in this example, KDEDOCS is not left unchanged. unset KDEDOCS echo $KDEDOCS # there is no output KDEDOCS=${KDEDOCS:-default} echo $KDEDOCS # output is 'default' default unset KDEDOCS > First off, let me demonstrate with a sample:
>
> KDEDOCS=${KDEDOCS:-default}
>
> The :- says that if KDEDOCS is unset (or is set to a null value),
> then to use default as the result. The original variable is left
> unchanged.
Unfortunately, in this example, KDEDOCS is not left unchanged.
unset KDEDOCS
echo $KDEDOCS
# there is no output
KDEDOCS=${KDEDOCS:-default}
echo $KDEDOCS
# output is ‘default’
default
unset KDEDOCS

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