Conditionals in BASH

[Rick Stevens]

Matthew Saltzman wrote:
> The conditionals && and || in bash are short-circuit, so that once a
> term is evaluated that determines the success or failure of the entire
> expression, evaluation of the remaining alternatives is skipped.
> 
> In a test expression (enclosed in [ ... ]), are the conditionals -a and
> -o also short-circuit?  The O'Reilly BASH book seems to suggest that
> they are not, but the description seems to me to be ambiguous.

To my knowledge, all conditionals are evaluated left-to-right.  As
soon as one comparison fails, there is no need to evaluate the remainder
as the true-false condition has been met and the test is aborted with
a "false" result.  The only time the right-most comparison (or top level
comparison if nested) is evaluated is if all other comparisons are
true.

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- Rick Stevens, Systems Engineer                       rps2 at nerd.com -
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