Path: csiph.com!goblin2!goblin1!goblin.stu.neva.ru!usenet.stanford.edu!not-for-mail From: Chris Elvidge Newsgroups: gnu.bash.bug Subject: Re: Return from function depending on number of parameters Date: Sat, 4 Jul 2020 11:44:22 +0100 Lines: 57 Approved: bug-bash@gnu.org Message-ID: References: <4766f763-84b7-f018-f925-7c6390ed7523@archlinux.org> NNTP-Posting-Host: lists.gnu.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: usenet.stanford.edu 1593878709 21161 209.51.188.17 (4 Jul 2020 16:05:09 GMT) X-Complaints-To: action@cs.stanford.edu To: bug-bash@gnu.org Envelope-to: bug-bash@gnu.org X-Injected-Via-Gmane: http://gmane.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=116.202.254.214; envelope-from=gnu-bug-bash-3@m.gmane-mx.org; helo=ciao.gmane.io X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/04 12:00:04 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: 59 X-Spam_score: 5.9 X-Spam_bar: +++++ X-Spam_report: (5.9 / 5.0 requ) BAYES_00=-1.9, DATE_IN_PAST_03_06=1.592, DKIM_ADSP_CUSTOM_MED=0.001, FORGED_GMAIL_RCVD=1, FORGED_MUA_MOZILLA=2.309, FREEMAIL_FORGED_FROMDOMAIN=1, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=1, NML_ADSP_CUSTOM_MED=0.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: reject X-BeenThere: bug-bash@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Bug reports for the GNU Bourne Again SHell List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Mailman-Original-Message-ID: X-Mailman-Original-References: <4766f763-84b7-f018-f925-7c6390ed7523@archlinux.org> Xref: csiph.com gnu.bash.bug:16537 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 is obsolete and that $((...))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 info on histexpand and the advice on bug reporting. Obviously I didn't read the manual - I didn't know about histexpand. Should that be 'set +o histexpand' to turn it off? -- Chris Elvidge England