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Re: Shell case statements

From: Chet Ramey
Subject: Re: Shell case statements
Date: Fri, 20 May 2011 14:19:26 -0400
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv: Gecko/20110414 Thunderbird/3.1.10

On 5/20/11 12:10 PM, Eric Blake wrote:
> On 05/20/2011 09:33 AM, Chet Ramey wrote:
>>> Well, that's rather all over the place, but yes, it does seem like bash
>>> was the buggiest of the lot, compared to other shells.  Interactively, I
>>> tested:
>>> readonly x=1
>>> case 1 in $((x++)) ) echo hi1 ;; *) echo hi2; esac
>>> echo $x.$?
>>> bash 4.1 printed:
>>> bash: x: readonly variable
>>> hi1
>>> 1.0
>>> which means it matched '1' to $((x++)) before reporting the failure
>>> assign to x, and the case statement succeeded.  Changing the first "1"
>>> to any other string printed hi2  (the * case).
>> Thanks for the report.  This was an easy fix.  The variable assignment
>> error was actually handled correctly, the expression evaluation code
>> just didn't pay enough attention to the result.
> How about the even simpler:
> $ bash -c 'readonly x=5; echo $((x=5))'; echo $?

That's not simpler, that's exactly the same case: a variable assignment
error during expression evaluation for arithmetic expansion.

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/

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