Mangling of '\\' by cygwin dll

Mangling of '\\' by cygwin dll

[Volker Quetschke]

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Hi,

I run into a strange problem while using sed from a cmd.exe shell.

The problem is not sed specific and the following lines demonstrate
it with /bin/echo.

 From cmd.exe:
C:\>\cygwin\bin\echo.exe '1 \ 2 \\ 3 \\\ 4 \\\\ 5 \\\\\ 6 \t'
1 \ 2 \ 3 \\ 4 \\ 5 \\\ 6 \t

It looks like each \\ is translated into \. Like escaping for
special characters, but it doesn't happen for single \.

This effect doesn't happen in bash:
$ /bin/echo.exe '1 \ 2 \\ 3 \\\ 4 \\\\ 5 \\\\\ 6 \t'
1 \ 2 \\ 3 \\\ 4 \\\\ 5 \\\\\ 6 \t

Bug or feature? I didn't find anything about this in
<http://cygwin.com/cygwin-ug-net/using-specialnames.html>.

Ah, yes,
$ uname -s -r
CYGWIN_NT-5.1 1.5.10(0.116/4/2)

Volker

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Re: Mangling of '\\' by cygwin dll

[Volker Quetschke]

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Hi
> I run into a strange problem while using sed from a cmd.exe shell.
> 
> The problem is not sed specific and the following lines demonstrate
> it with /bin/echo.

The following mini program also demonstrates that it comes from
the cygwin dll.
-- slashtest.c --
#include <stdio.h>
int main(int argc, char *argv[])
{  printf("Arg1:%s:\n",argv[1]);
   return 0;
}
-- slashtest.c end --

Compile it with "gcc slashtest.c -o slashtest_cyg.exe" and
"gcc -mno-cygwin slashtest.c -o slashtest_w32.exe" and try
the following from a cmd.exe:

C:\cygwin\bin>\cygwin\home\quetschke\slashtest_w32.exe '\\\'
Arg1:'\\\':
_nothing done for a native binary, the quotes stay_

C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe '\\\'
Arg1:\':
_Hmm, one \ escaped and one ' escaped, quotes vanish if not
escaped._

C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe \\\
Arg1:\\\:
_Nothing special for a non-quoted string._

What is the deeper plan for this functionality?

Volker

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Re: Mangling of '\\' by cygwin dll

[Corinna Vinschen]

On Jul 25 15:15, Volker Quetschke wrote:
> Hi
> >I run into a strange problem while using sed from a cmd.exe shell.
> >
> >The problem is not sed specific and the following lines demonstrate
> >it with /bin/echo.
> 
> The following mini program also demonstrates that it comes from
> the cygwin dll.
> -- slashtest.c --
> #include <stdio.h>
> int main(int argc, char *argv[])
> {  printf("Arg1:%s:\n",argv[1]);
>   return 0;
> }
> -- slashtest.c end --
> 
> Compile it with "gcc slashtest.c -o slashtest_cyg.exe" and
> "gcc -mno-cygwin slashtest.c -o slashtest_w32.exe" and try
> the following from a cmd.exe:
> 
> C:\cygwin\bin>\cygwin\home\quetschke\slashtest_w32.exe '\\\'
> Arg1:'\\\':
> _nothing done for a native binary, the quotes stay_
> 
> C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe '\\\'
> Arg1:\':
> _Hmm, one \ escaped and one ' escaped, quotes vanish if not
> escaped._
> 
> C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe \\\
> Arg1:\\\:
> _Nothing special for a non-quoted string._
> 
> What is the deeper plan for this functionality?

Quotes are not treated specially in cmd.  But they are used in Cygwin
to allow applications called from cmd to get values which are otherwise
difficult to transport.  The rules are fairly simple and match your
obvservations.  A backslash is always a special character.  So a real
backslash has to be written as \\, the quoting character itself as
either \' or \", whatever you used for it.  That's it, basically.  So
your example '\\\' is treated as an unfinished quote with two characters,
a backslash and a single quote.


Corinna

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RE: Mangling of '\\' by cygwin dll

[Tawee Laoitichote]

unsubscribe

-----Original Message-----
From: cygwin-owner@cygwin.com [mailto:cygwin-owner@cygwin.com] On Behalf
Of Corinna Vinschen
Sent: Wednesday, July 28, 2004 3:41 PM
To: cygwin@cygwin.com
Subject: Re: Mangling of '\\' by cygwin dll


On Jul 25 15:15, Volker Quetschke wrote:
> Hi
> >I run into a strange problem while using sed from a cmd.exe shell.
> >
> >The problem is not sed specific and the following lines demonstrate 
> >it with /bin/echo.
> 
> The following mini program also demonstrates that it comes from the 
> cygwin dll.
> -- slashtest.c --
> #include <stdio.h>
> int main(int argc, char *argv[])
> {  printf("Arg1:%s:\n",argv[1]);
>   return 0;
> }
> -- slashtest.c end --
> 
> Compile it with "gcc slashtest.c -o slashtest_cyg.exe" and "gcc 
> -mno-cygwin slashtest.c -o slashtest_w32.exe" and try the following 
> from a cmd.exe:
> 
> C:\cygwin\bin>\cygwin\home\quetschke\slashtest_w32.exe '\\\'
> Arg1:'\\\':
> _nothing done for a native binary, the quotes stay_
> 
> C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe '\\\'
> Arg1:\':
> _Hmm, one \ escaped and one ' escaped, quotes vanish if not escaped._
> 
> C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe \\\
> Arg1:\\\:
> _Nothing special for a non-quoted string._
> 
> What is the deeper plan for this functionality?

Quotes are not treated specially in cmd.  But they are used in Cygwin to
allow applications called from cmd to get values which are otherwise
difficult to transport.  The rules are fairly simple and match your
obvservations.  A backslash is always a special character.  So a real
backslash has to be written as \\, the quoting character itself as
either \' or \", whatever you used for it.  That's it, basically.  So
your example '\\\' is treated as an unfinished quote with two
characters, a backslash and a single quote.


Corinna

-- 
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Red Hat, Inc.

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Re: Mangling of '\\' by cygwin dll

[Volker Quetschke]

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Hi Corinna,

>>C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe '\\\'
>>Arg1:\':
>>_Hmm, one \ escaped and one ' escaped, quotes vanish if not
>>escaped._
>>
>>C:\cygwin\bin>\cygwin\home\quetschke\slashtest_cyg.exe \\\
>>Arg1:\\\:
>>_Nothing special for a non-quoted string._
>>
>>What is the deeper plan for this functionality?
> 
> Quotes are not treated specially in cmd.  But they are used in Cygwin
> to allow applications called from cmd to get values which are otherwise
> difficult to transport.  The rules are fairly simple and match your
> obvservations.  A backslash is always a special character.  So a real
> backslash has to be written as \\, the quoting character itself as
> either \' or \", whatever you used for it.  That's it, basically.  So
> your example '\\\' is treated as an unfinished quote with two characters,
> a backslash and a single quote.
Thanks, yes my small sed problem showed me that I also had to escape
the used \s in that file even though the single \ was conserved it
somehow confused sed.

Consequently using \\ fixes this.

Volker


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