Path: csiph.com!xmission!news.snarked.org!news.linkpendium.com!news.linkpendium.com!panix!usenet.stanford.edu!not-for-mail
From: Chris Elvidge <celvidge001@gmail.com>
Newsgroups: gnu.bash.bug
Subject: Re: Return from function depending on number of parameters
Date: Sat, 4 Jul 2020 12:54:03 +0100
Lines: 61
Approved: bug-bash@gnu.org
Message-ID: <mailman.934.1593863651.2574.bug-bash@gnu.org>
References: <b1c19d38-64c0-f1ae-d08a-1ada435a0022@gmail.com> <4766f763-84b7-f018-f925-7c6390ed7523@archlinux.org> <73b2d4c9-badf-e059-3a77-57d2f9ef197b@gmail.com>
NNTP-Posting-Host: lists.gnu.org
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
To: Eli Schwartz <eschwartz@archlinux.org>, bug-bash@gnu.org
Envelope-to: bug-bash@gnu.org
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1
In-Reply-To: <4766f763-84b7-f018-f925-7c6390ed7523@archlinux.org>
Content-Language: en-GB
Received-SPF: pass client-ip=2a00:1450:4864:20::32b; envelope-from=celvidge001@gmail.com; helo=mail-wm1-x32b.google.com
X-Spam_score_int: -17
X-Spam_score: -1.8
X-Spam_bar: -
X-Spam_report: (-1.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN
X-Spam_action: no action
X-BeenThere: bug-bash@gnu.org
X-Mailman-Version: 2.1.23
Precedence: list
List-Id: Bug reports for the GNU Bourne Again SHell <bug-bash.gnu.org>
List-Unsubscribe: <https://lists.gnu.org/mailman/options/bug-bash>, <mailto:bug-bash-request@gnu.org?subject=unsubscribe>
List-Archive: <https://lists.gnu.org/archive/html/bug-bash>
List-Post: <mailto:bug-bash@gnu.org>
List-Help: <mailto:bug-bash-request@gnu.org?subject=help>
List-Subscribe: <https://lists.gnu.org/mailman/listinfo/bug-bash>, <mailto:bug-bash-request@gnu.org?subject=subscribe>
X-Mailman-Original-Message-ID: <73b2d4c9-badf-e059-3a77-57d2f9ef197b@gmail.com>
X-Mailman-Original-References: <b1c19d38-64c0-f1ae-d08a-1ada435a0022@gmail.com> <4766f763-84b7-f018-f925-7c6390ed7523@archlinux.org>
Xref: csiph.com gnu.bash.bug:16533

On 03/07/2020 11:16 pm, Eli Schwartz wrote:
> On 7/3/20 2:00 PM, Chris Elvidge wrote:
>> I've used 'return $((!$#))' and 'return $[!$#]' to return an error if no
>> parameters given to function.
>>
>> Tested in a bash script 'exit $((!$#)) / $[!$#]' - both work.
>>
>> 'echo  $((!$#)) / $[!$#]' - both echo 1 when no params, 0 when any
>> number of params.
>>
>> I'm told ( https://wiki.bash-hackers.org/scripting/obsolete ) that
>> $[...] is obsolete and that $((...)) should be used instead. OK so far.
>>
>> However 'N=0; echo $((!$N))' gives an error at the bash prompt. 'echo
>> $[!$N]' echo's 1 as expected.
> 
> "gives an error" is a useless bug report. It works for me.
> 
> $ N=0; echo $((!$N))
> 1
> 
> My initial reaction to reading this thread is head scratching!
> 
> As the other reply mentioned, there's actually a good explanation for
> why we get different results -- I disabled an annoying feature.
> 
> $ set -o histexpand
> 
> Now here's a useful bug report. "When I run this, I get the following
> incorrect results or error message":
> 
> $ N=0; echo $((!$N))
> N=0; echo $((histexpandN))
> 0
> $ N=0; echo $((!$N))
> N=0; echo $(()N))
> -bash: syntax error near unexpected token `)'
> $ N=0
> $ echo $((!$N))
> echo $((N=0N))
> -bash: N=0N: value too great for base (error token is "0N")
> 
> ...
> 
>  From there, people can give useful advice for solving the problem. (My
> preferred advice is "disable histexpand".)
> 

Thanks for the pointers to a better bug report.
And thanks for the info on histexpand. I obviously should read the 
manual more carefully - I'd never come across it - as it's set by 
default, not in any profile or bashrc file.
Did you mean set +o histexpand to disable the feature?


-- 

Chris Elvidge