Invoking system commands... "A better way?"

**The_Muffin_Man** · 06-09-2004

Hey... I always hear that it's considered bad to use system commands. It seems like you sometimes have to use a dos or unix command! However, I have also noticed that you can't use a string variable to call the system command.

Gives an error:

Code:

#include <stdlib.h>
#include <iostream.h>

int main()
{
char SystemCommand[] = "copy C:\file.txt C:\newfolder\file.txt";
system(SystemCommand);
return 0;
}

Doesn't give an error:

Code:

#include <stdlib.h>
#include <iostream.h>

int main()
{
system("copy C:\file.txt C:\newfolder\file.txt");
return 0;
}

Is there a way to use a string variable to call a system command, like I wanted to in the first code block?

Thanks,
The_Muffin_Man

**prog-bman** · 06-09-2004

Hmmmm compiles for me with this change

Code:

#include <stdlib.h>
#include <iostream>
using namespace std;

int main()
{
char SystemCommand[] = "copy C:\file.txt C:\newfolder\file.txt";
system(SystemCommand);
return 0;
}

**The_Muffin_Man** · 06-09-2004

I'm sorry... but that's wierd. Why would using the ANSI standard header files with declare the namespace std make a drastic difference? Maybe my compiler's header files are messed up. Thanks for helping. Did it work with using the <iostream.h> instead of the <iostream>?

**prog-bman** · 06-09-2004

Nope i got a backwards warning are ya using dev c++?

**The_Muffin_Man** · 06-09-2004

Yes for windows I am. I also use gcc for linux, but I haven't tried it for linux.

**prog-bman** · 06-09-2004

oh and btw you might want to make your char into a const char* cause thats what system uses

Code:

//Taken From Header
int system(const char*);

And one more thing for more standards compliant

Code:

#include <cstdlib>
#include <iostream>
using namespace std;

**The_Muffin_Man** · 06-09-2004

Thanks a million! By the way, is there anything wrong if I wanted to include a non-standard header file like windows.h with ANSI standard header files. Somebody told me that this is bad practice.
for example:
#include <cstdlib>
#include <iostream>
#include <windows.h> <----- Bob says, " uh oh! That's a bad thing!"

Is this okay?

**prog-bman** · 06-09-2004

Windows is its own deal if ya want to use it that is the way to.
but c++ knows nothing of windows so your not standards compliant cause that code won't work on non-windows system(duh)

**Thantos** · 06-09-2004

try:

Code:

char SystemCommand[] = "copy C:\\file.txt C:\\newfolder\\file.txt"

And a tip, don't just say it gives an error. Tell us what the error is.

**The_Muffin_Man** · 06-09-2004

oh yeah, I'm sorry about that backslash thing... I'm just so used to linux where I would say:

Code:

char SystemCommand[] = "cp /home/file.txt /home/newfolder/file.txt";

So sorry. That wasn't intended. I was just in a rush. But thanks for your guys suggestions. You people were very helpful.

**Sang-drax** · 06-10-2004

The following is standard C++:

Code:

  #include <cstdlib>
#include <iostream>
using namespace std;

int main()
{
char SystemCommand[] = "copy C:\\file.txt C:\\newfolder\\file.txt";
system(SystemCommand);
return 0;
}

If this doesn't work, your compiler doesn't follow the standard.

What was the error message of the first example? Judging from the two examples, your compiler seems strange.

prog-bman: A (char[]) can be converted to a (const char[]) without any cast.

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