system mkdir

system mkdir

[Fitzy]

 Hello,
  I have a program which I wrote using Visual Studio 2010, everything
works fine there.
Now I'm trying to get it all running properly under Cygwin.  It is
compiling successfully, but the following does not work:
system("mkdir temp");
I use this to create a temporary directory to which temporary files
are written.  It is then deleted when the program is finished.
 Under VS this command works, under Cygwin it does nothing.  I've
tried various alternatives
"sudo mkdir temp" etc...
 But can't find anything that will programatically create a directory
under Cygwin.

 Does anyone know how to do this?

Thank you!

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Re: system mkdir

[Christopher Faylor]

On Mon, Nov 28, 2011 at 01:31:26PM -0700, Fitzy wrote:
>?Hello,
>? I have a program which I wrote using Visual Studio 2010, everything
>works fine there.
>Now I'm trying to get it all running properly under Cygwin. ?It is
>compiling successfully, but the following does not work:
>system("mkdir temp");
>I use this to create a temporary directory to which temporary files
>are written. ?It is then deleted when the program is finished.
>?Under VS this command works, under Cygwin it does nothing. ?I've
>tried various alternatives
>"sudo mkdir temp" etc...
>?But can't find anything that will programatically create a directory
>under Cygwin.
>
>?Does anyone know how to do this?

Yes.  Use the mkdir() function.  That is, in fact, very similar to how it
should be done in Visual Studio too.

cgf

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Re: system mkdir

[Eric Blake]

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On 11/28/2011 01:33 PM, Christopher Faylor wrote:
>> ?But can't find anything that will programatically create a directory
>> under Cygwin.
>>
>> ?Does anyone know how to do this?
> 
> Yes.  Use the mkdir() function.  That is, in fact, very similar to how it
> should be done in Visual Studio too.

For a temporary directory, mkdtemp() might be better than mkdir(); but
either way, you still have to use rmdir() to clean up after you are done.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: system mkdir

[Peter Brown]

Eric Blake <eblake <at> redhat.com> writes:

> 
> On 11/28/2011 01:33 PM, Christopher Faylor wrote:
> >> ?But can't find anything that will programatically create a directory
> >> under Cygwin.
> >>
> >> ?Does anyone know how to do this?
> > 
> > Yes.  Use the mkdir() function.  That is, in fact, very similar to how it
> > should be done in Visual Studio too.
> 
> For a temporary directory, mkdtemp() might be better than mkdir(); but
> either way, you still have to use rmdir() to clean up after you are done.
> 

This seems to work for me.

int MySystem(char *s)
{
  int answer;
  char syscmd[2048];
  sprintf(syscmd,"cmd /c bash -c 'umask 0077;%s'",s);
  answer = system( syscmd );
  return answer;
}




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Re: system mkdir

[Eric Blake]

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On 12/01/2011 04:32 PM, Peter Brown wrote:
>>> Yes.  Use the mkdir() function.  That is, in fact, very similar to how it
>>> should be done in Visual Studio too.

I still say using mkdir() is the right solution - use a simple function,
rather than a call to system().

> This seems to work for me.
> 
> int MySystem(char *s)
> {
>   int answer;
>   char syscmd[2048];
>   sprintf(syscmd,"cmd /c bash -c 'umask 0077;%s'",s);
>   answer = system( syscmd );
>   return answer;

Ouch. A thousand times NOOOOO. DON'T DO THAT.  You just made a HUGE
security hole.  All I have to do is call:

MySystem("rm -rf /");

and I've nuked your system.  Or, I could call MySystem(<string longer
than 2048 bytes>) and stack overflow you.  Or any other number of flaws.

And even if those weren't issues, you ruined my quoting.  I should be
able to do system("echo 'a  b'") and get "a  b" on stdout, but the way
you butchered quoting, my single quotes terminate the argument to cmd,
and completely hose things.

You DON'T want to use system() unless absolutely necessary, and then
only with proper quoting.  And you don't want to use sprintf on
arbitrary input; stick to snprintf, or to asprintf.  And seriously -
calling cmd /c just to call bash just to call commands that will be
interpreted by bash, when you could have just used commands interpreted
by bash to begin with?  If system() isn't calling cygwin's /bin/sh, then
you aren't using cygwin properly.  Don't make it worse by wrapping
system() to go through another two layers of quoting nightmares.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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