Re: one shell command doesn't return result

Thank you very much !

Eli Zaretskii a écrit :
>> Date: Sun, 15 Jun 2008 16:34:16 +0200
>> From: "[email protected]" <[email protected]>
>>
>> I would like to make a simple calculation in my makefile, but I have a strange problem.
>> On windows, I use the DOS command "set /A 3*100+13/2", it works on a shell and returns "306" but not in my makefile. I have make a simple makefile to test it :
>>
>> --------------------------------------------------
>> # command to make a mathematical operation
>> CMD_MATH:=$(shell set /A 3*100+13/2)
>> # command to list files
>> CMD_FILES:=$(shell dir /b/a-d/-W)
>>
>> all::
>> 	@echo CMD_MATH:$(CMD_MATH)
>> 	@echo CMD_FILES:$(CMD_FILES)
>> --------------------------------------------------
>>
>> It returns me :
>>
>> --------------------------------------------------
>> CMD_MATH:
>> CMD_FILES:Makefile Makefile~
>> --------------------------------------------------
>>
>> One command returns correctly the result but not the command "set /A" which returns nothing.
>> I have GNU Make 3.81
> 
> This is expected behavior.  "set /?" has this small print among its
> text:
> 
>     If SET /A is executed from the command line outside of a command
>     script, then it displays the final value of the expression.
> 
> Note the "outside of a command script" condition: this is the cause of
> your surprise.  When Make uses cmd.exe as the shell, it invokes all
> the commands through temporary batch files (a.k.a. command scripts);
> you can see that if you invoke Make with the --debug=j switch.  And
> when "set /a" is invoked from a batch file, it does not print the
> result.
> 
> The following trick will do what you want:
> 
>   CMD_MATH:=$(shell cmd.exe /c "set /A 3*100+13/2")
> 
>