From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailsrv.cs.umass.edu (mailsrv.cs.umass.edu [128.119.240.136]) by sourceware.org (Postfix) with ESMTPS id 6E9E93857C5E for ; Sat, 5 Sep 2020 22:25:31 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 6E9E93857C5E Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=cs.umass.edu Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=moss@cs.umass.edu Received: from [192.168.0.30] (c-24-62-203-86.hsd1.ma.comcast.net [24.62.203.86]) by mailsrv.cs.umass.edu (Postfix) with ESMTPSA id D4784401F19D; Sat, 5 Sep 2020 18:25:30 -0400 (EDT) Reply-To: moss@cs.umass.edu Subject: Re: Is this a bug in bash? To: Bob McGowan , The Cygwin Mailing List References: <50fad2a4-22c3-8de8-3a0a-394c0b95048b@gmail.com> <824c5748-594e-cf7c-4bba-4b70f9f593b1@cs.umass.edu> <08b7a77e-6d88-9729-39c1-dc3583cf06ad@gmail.com> From: Eliot Moss Message-ID: <4f114ddb-1e74-8ba3-11e0-1e186a8468a3@cs.umass.edu> Date: Sat, 5 Sep 2020 18:25:31 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: <08b7a77e-6d88-9729-39c1-dc3583cf06ad@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-2.7 required=5.0 tests=BAYES_00, BODY_8BITS, KAM_DMARC_STATUS, NICE_REPLY_A, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: cygwin@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 05 Sep 2020 22:25:32 -0000 On 9/5/2020 3:18 PM, Bob McGowan wrote: > On 9/5/2020 8:44 AM, Eliot Moss wrote: >> On 9/5/2020 11:29 AM, Greg Borbonus via Cygwin wrote: >> > Out of curiosity, why are there 2 different sets of quotes? >> > >> > Thanks, >> > Greg Borbonus >> > >> > On Fri, Sep 4, 2020, 10:23 PM Bob McGowan via Cygwin >> > wrote: >> > >> >> I am trying to set things up so the Bash profile detects if bash is >> >> running from the Windows "XWin Server" startup link or not. The startup >> >> link has the following as the command: >> >> >> >> C:\cygwin64\bin\run.exe --quote /usr/bin/bash.exe -l -c "cd; exec >> >> /usr/bin/startxwin" >> >> >> >> So I thought I'd try adding the env command to set an environment variable: >> >> >> >> C:\cygwin64\bin\run.exe --quote /usr/bin/env startxwin=yes >> >> /usr/bin/bash.exe -l -c "cd; exec /usr/bin/startxwin" >> >> >> >> This works (if there's a better way, I'd be happy to learn of it) but in >> >> the process of testing I had a problem when echo'ing the variable. >> >> >> >> For purposes of describing the bug, I simplified the command as follows: >> >> >> >>       env startup=yes bash -l -c 'echo "cmd:  $startup"' >> >> >> >> I also added an "echo profile: $startup" to the .bash_profile file. >> >> >> >> When I run the above in a Cygwin shell, the output is: >> >> >> >> $ env startup=yes bash -l -c "echo cmd: $startup" >> >> profile: yes >> >> $ >> >> >> >> When I run it in a Linux shell, the output is: >> >> >> >> $ env startup=yes bash -l -c 'echo "cmd:  $startup"' >> >> profile: yes >> >> cmd:  yes >> >> $ >> >> >> >> As you can see, the Cygwin side fails to generate any output from the -c >> >> echo command but on the Linux system there is output. >> >> >> >> Normally I'd call this a bug but since this is running under Windows it >> >> may be some weirdness of the implementation required to create the Linux >> >> like environment. >> >> >> >> The Bash version in Cygwin is  4.4.12(3)-release and for my Debian Linux >> >> system, it is 5.0.3(1)-release.  So it could also be that it existed in >> >> Linux 4.x series and has been fixed in the 5.x series. >> >> The inner quotes are necessary because there are two spaces beween cmd: and >> $startup, and the : may be risky unquoted in bash (actually it is ok, but I >> try to be careful about anything not a letter or digit, etc.). The outer ones >> are single quotes, which protect $startup from being expanded before it gets >> to the new bash.  " " (double) quotes do not prevent $ expansion. (You want >> the new bash to do the expansion.)  However, I think this would also work: >> >>     env startup=yes bash -l -c echo 'cmd:  $startup' >> >> Regards - Eliot Moss > > Actually this won't work, because the -c option to bash only takes one argument, so in this case > bash would execute the 'echo', you'd get a blank line, and the rest would be ignored. > > You need to put the first single quote before the echo command: > >     env startup=yes bash -l -c 'echo cmd:  $startup' > > I put in the second set of quote entirely because of the double space after the colon.  I just like > to be grammatically correct ;) but as you say, they are not relevant to the actual execution of the > command. > > And for the command stored in the Windows shortcut, there are no colons or variables, so only one > set of quotes need to be used. And I believe Windows only cares about double quotes so they are used > here: > >     C:\cygwin64\bin\run.exe --quote /usr/bin/env startxwin=yes /usr/bin/bash.exe -l -c "cd; exec > /usr/bin/startxwin" > > Apologies for any confusion this may have caused. Quote right that the -c command needs to be quoted with all of its arguments! EM