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 <cygwin@cygwin.com>
> 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
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