[prog] bash: string comparisons in conditionals
riccarda.cassini at gmx.de
Thu Apr 22 13:49:33 EST 2004
Conor Daly wrote:
> On Thu, Apr 22, 2004 at 01:05:37AM +0200 or thereabouts, Riccarda Cassini
> > I seem to be getting the same correct results for all kinds of input
> > with all of the following variations:
> > [ ! "$a" ]
> > [ -z "$a" ]
> > [ "$a" = "" ]
> > [ x"$a" = x ]
> > [ "x$a" = x ]
> > [ "x$a" = "x" ]
> BTW, a little something to add to your arsenal:
> How does the shell distinguish between the variable 'ax' and the variable
> 'a' followed by the letter 'x'?
I guess if I'd work out all functionally equivalent permutations, I'd
end up with at least 16 valid tests for 'string being empty', not
counting symmetrical '='-versions, '==', and letters other than 'x'
(but allowing single quotes around the x)...
Who said that perl is the TMTOWTDI language? ;-)
> The braces delimit a variable name to allow non-whitespace characters to
good to know - works the same way in perl, btw.
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