thanks you all.
On 3/5/06, Andreas Schwab <schwab@xxxxxxx> wrote:
> "June Fang" <june.fang@xxxxxxxxx> writes:
>
> > i know ${ZSH_VERSION} means variable substituting;
> > and ${ZSH_VERSION:+set} means "If parameter is null or unset, nothing
> > ~~ Note the `:`
> > is substituted, otherwise the expansion of word is substituted."
> > ---- from Bash reference manual
> >
> > but what dose ${ZSH_VERSION+set} without the `:` means ?
>
> See the Bash menual (same section):
>
> When not performing substring expansion, Bash tests for a parameter
> that is unset or null; omitting the colon results in a test only for a
> parameter that is unset. Put another way, if the colon is included,
> the operator tests for both existence and that the value is not null;
> if the colon is omitted, the operator tests only for existence.
>
> Andreas.
>
> --
> Andreas Schwab, SuSE Labs, schwab@xxxxxxx
> SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
> PGP key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
> "And now for something completely different."
>
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