Re: configure script question ?

[Andreas Schwab]

"June Fang" <address@hidden> 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, address@hidden
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