Re: the fine art of error chek'n

[Alan D. Salewski]

On 2020-05-07 15:39:05, address@hidden spake thus:
> i have written simple programs use'n bash for many years
> i most always use something like
> 
> false
> if (($? != 0)); then echo failed; fi
> 
> other than readability what is the difference in the above and
> 
> false || echo failed

The arithmetic expression is less portable to other Bourne-family shells. For
example, here is what dash does with it:

    $ false || echo failed
    failed

    $ false
    $ if (($? != 0)); then echo failed; fi
    /bin/dash: 10: 1: not found

A portable way to do the same check would be:

    $ false
    $ if test $? -ne 0; then echo failed; fi
    failed

The shell portability chapter of the GNU Autoconf manual has a section that
discusses the different ways parentheses are treated by different shells:

    11.10 "Parentheses in Shell Scripts"
    
https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/autoconf.html#Parentheses

Take care,
-Al

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