Using a system command with parameter from program in C++

Question

So I'm doing a project for school and was trying to use the windows function "mkdir", but the directory name would be a string given by the program. Here's the (not very useful) code:

string c,a;
cin>>c;
if(c.compare("mkdir")==0)
    cin>>a;
    system("mkdir"); //here I want to make the directory
}

They're [simpler ways](https://msdn.microsoft.com/fr-fr/library/windows/desktop/aa363855(v=vs.85).aspx) to create directories... — YSC, Nov 30 '17 at 14:02
On which operating system? I am surprised you are given this homework on Windows (however, coding a shell on Linux is a very common homework). — Basile Starynkevitch, Nov 30 '17 at 14:52

score 3 · Answer 1 · answered Nov 30 '17 at 14:13

3

As others have mentioned, it would be better to create the directory without using the system call. If you would like to use that method regardless, you need to build a command string which includes your arguments prior to passing it to system.

char command[100];
sprintf(command, "mkdir %s", a);
system(command);

answered Nov 30 '17 at 14:13

user2530302

31
1

I recommend using `snprintf(command, sizeof(command), "mkdir %s", a);` – Basile Starynkevitch Nov 30 '17 at 14:43

Basile Starynkevitch · Accepted Answer · 2017-11-30T14:45:34.370

Directories don't exist for the C++11 (or C++14) standard. Later C++ standard (e.g. C++17 ...) might offer the std::filesystem library.

You could use operating system specific primitives. On Linux and POSIX, consider the mkdir(2) system call (and CreateDirectory function on Windows).

You could find framework libraries (e.g. POCO, Qt, Boost, ....) wrapping these, so with these libraries you won't care about OS specific functions.

but the directory name would be a string given by the program.

Then you could consider building a command as a runtime C string for system(3). E.g. with snprintf(3) (or with some std::string operation). Beware of code injection (e.g. think of the malicious user providing /tmp/foo; rm -rf $HOME as his directory name on Linux)!

Ashwel · Answer 3 · 2017-11-30T14:30:20.097

1

If you want create folder use WinApi see CreateFolder

edited Nov 30 '17 at 14:30

answered Nov 30 '17 at 14:06

Ashwel

1,194
9
16

score 0 · Answer 4 · answered Nov 30 '17 at 14:26

The simplest solution I can think of:

string c;
cin >> c;
if(c == "mkdir") {
    string a;
    cin >> a;
    system("mkdir " + a);
}

But if this project involves writing some kind of command shell, system is very likely off-limits and you're expected to use the operating system's API directly.

Using a system command with parameter from program in C++

4 Answers4