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Re: [PATCH] Fix parameter passing containing quote/equal to Windows batch command
- From: VÃclav Zeman <vhaisman at gmail dot com>
- To: cygwin-patches at cygwin dot com
- Date: Tue, 21 Jan 2014 13:31:25 +0100
- Subject: Re: [PATCH] Fix parameter passing containing quote/equal to Windows batch command
- Authentication-results: sourceware.org; auth=none
- References: <CABDpyCh3VMDmd4Rb64Fz-cb2HzUwtZ0cY9T3xWUC8_O-eqKO6Q at mail dot gmail dot com> <52DDBFBE dot 2010800 at gmail dot com>
On 21 January 2014 01:30, Max Polk wrote:
> On 1/20/2014 1:02 AM, Daniel Dai wrote:
>>
>> We notice one issue when running a Windows batch command inside
>> cygwin. Here is one example.
>>
>> Simple batch file:
>> a.bat:
>> echo %1
>>
>> Run it under cygwin:
>> ./a.bat a=b
>> a
>>
>> ./a.bat "a=b"
>> a
>>
>> If we pass additional \"
>> ./a.bat "\"a=b\""
>> "\"a
>>
>> There seems no way to pass a=b into bat.
>
>
> This is how batch files work, and likely not a problem with Cygwin:
> http://support.microsoft.com/kb/35938
> Excerpt: "it is not possible to include an equal sign as an argument to a
> batch file"
>
> Be careful to note that cmd.exe and .bat files naturally split a=b into two
> arguments and strip out the equals sign:
>
> (Run from cmd.exe)
> C:\>Argecho.bat a=b
> FIRST a
> SECOND b
> THIRD
>
> I did notice that adding double quotes (in cmd.exe) will make will it arrive
> as one argument, and note that the double quotes are still there:
>
> (Run from cmd.exe)
> C:\>Argecho.bat "a=b"
> FIRST "a=b"
> SECOND
> THIRD
>
> There is a problem getting Cygwin the above test case, however.
>
> The test script was:
> C:\>type Argecho.bat
> @echo off
> echo FIRST %1
> echo SECOND %2
> echo THIRD %3
>
> When run from Cygwin bash, and you force the double quotes by surrounding
> double quotes "a=b" with single quotes '"a=b"', you seem to get too *many*
> quotes in the batch file:
>
> (Run from bash, the batch file behaves correctly as if run from cmd.exe)
> $ Argecho.bat a=b
> FIRST a
> SECOND b
> THIRD
>
> (Run from bash, same as above since bash removes the double quotes prior to
> passing to program):
> $ Argecho.bat "a=b"
> FIRST a
> SECOND b
> THIRD
>
> (Run from bash, this is what is surprising double surrounded with single)
> $ Argecho.bat '"a=b"'
> FIRST "\"a
> SECOND b\""
> THIRD
>
> It seems that only the final test case above doesn't behave as expected.
Beware! The way CMD.exe handles command line and parameters is
different/incompatible from the way C (MSVCRT) application handles
them. Do not confuse the two. You cannot prove/show anything about how
C application handles arguments by using CMD.exe as a show case.
--
VZ