Re: Anonymous array indexing

["Bart Schaefer" <schaefer@xxxxxxxxxxxxxxxxxxxxxxx>]

On Dec 12,  6:41pm, Steve Talley wrote:
} 
} Is there a compact version of the following:
} 
}     fred=(one two three)
}     export FRED=$fred[2]
}     unset fred
} 
} so that I can avoid having to use the temporary variable fred.

The general trick is that the nameless parameter ${} always expands to the
empty string, so ${:-value} always expands to "value".  Then build up from
there.

} I am looking for something like
} 
}     export FRED=(one two three)[2]

The value in ${:-value} always starts out as a scalar (a string), so you
have to explicitly convert to an array before you can index it.

If the individual words of the array do not contain spaces, you can combine
word splitting ${=scalar} with ${:-value} to get:

	export FRED=${${=:-one two three}[2]}

If the words will have embedded spaces, you'll have to resort to some other
kind of splitting.  E.g., ${(f)...} splits at newlines, so you can do:

	export FRED=${${(f):-$'one\ntwo has spaces\nthree'}[2]}

This uses $'...' to turn \n into newlines, then splits on them.  However,
the $'...' syntax is not available in 3.0.x.  In all versions you can
instead split on some other character, e.g. on period:

	export FRED=${${(s(.)):-one.two has spaces.three}[2]}

I don't think there is a fully general solution that works when you can't
choose in advance a character on which to split.  However, I'm guessing
that the strings in the array are known in advance, and that it is the
subscript that might vary, so you should be able to work something out.

-- 
Bart Schaefer                                 Brass Lantern Enterprises
http://www.well.com/user/barts              http://www.brasslantern.com

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