Re: mod arithmetic result 0 gives error exit status

[Chris F.A. Johnson]

On Mon, 10 Oct 2005, Duane Ellis wrote:

> VERSION:
>        GNU bash, version 3.00.15(1)-release (i386-redhat-linux-gnu)
>        {came with Red Hat EL-4}
>
> Description:
>
>        Valid math operations results give an ERROR exit status.
>
> While this is a documented feature [4.2 of the info file]
>
>        If the last EXPRESSION evaluates to 0,
>        `let' returns 1; otherwise 0 is returned.
>
> grr grrr ... it was not expected, and bash treats it as an ERROR
>
>        bash$ let A=1-1
>        bash$ echo $?

     I treat "let" as an error, since it is not portable. Use the
     portable arithmetic syntax and you do not get an error:

A=$(( 1 - 1 ))


> Info file: "6.5 Shell Arithmetic" where available operators are
> listed implies that the only "error" that can occur is division by
> zero.
>
>        "[snip] with no check for overflow, though division
>        by 0 is trapped and flagged as an error."
>
> Implies otherwise.
>
> Thanks.
>
> Duane Ellis
>
>
>
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--
    Chris F.A. Johnson                     <http://cfaj.freeshell.org>
    ==================================================================
    Shell Scripting Recipes: A Problem-Solution Approach, 2005, Apress
    <http://www.torfree.net/~chris/books/cfaj/ssr.html>