How can I get the system drive letter?

Question

How would I find the driver letter of the main hard disk on a Windows Operating system?

That is, the drive with Program Files, System32, and so on.

Veratrine

Don't assume programs will be in "\Program Files", or system files in "\Windows\System32" - there are API calls to retrieve exact paths for these and more... – Michael

Can you give me an example of one of those API calls so I can research them? I am wanting to look for certain files associated with programs – Veratrine

msdn.microsoft.com/en-us/library/ms724373.aspx ... msdn.microsoft.com/en-us/library/bb762181.aspx – Michael

Answer 1

There's an environment variable called SystemDrive which is set to the system drive (surprisingly enough). The getenv() call is how you can get to it.

char *sysDrive = getenv ("SystemDrive");
if (sysDrive == NULL) {
    // vote me down.
} else {
    // vote me up and use it.
}

This page lists a whole slew of environment variables available if you can't rely on specific directories existing on the system drive.

Alternatively, use the Windows API call, SHGetSpecialFolderPath(), and pass in the correct CSIDL. Then you shouldn't have to rely on the environment variables.

Although take note on those pages that this has been superceded by other functions in Vista (it should still work since this function becomes a wrapper around the new one).

Brunner

Answer 2

The API Call GetWindowsDirectory could be of assistance. You can further parse this information using API's to parse the drive letter information.

Tolly

What APIs would I use to "further parse" the GetWindowsDirectory() results? – Gearalt

Just get the first letter of the windows directory path. – Modulation

Answer 3

SYSTEMDRIVE

PROGRAMFILES

SYSTEMROOT

WINDIR

Don't assume Program Files is on the same drive as Windows. It usually is. Usually.

Rhines

You should mention that those in caps are names for Windows environment variables. – Gearalt

Answer 4

Get the system drive letter by using the function _dupenv_s .

getenv "Function is not thread safe [concurrency-mt-unsafe]" and "This function or variable may be unsafe. Consider using _dupenv_s instead." - VS2019 Compiler Warning (level 3) C4996.

#include <iostream>

int main()
{
    char* system_drive{ nullptr };
    size_t count{ 0 };

    // _dupenv_s is a Microsoft function, designed as a more secure form of getenv:
    _dupenv_s(&system_drive, &count, "SystemDrive");

    std::cout << "system drive: " << system_drive << std::endl;

    // Note: It is the calling program's responsibility to free the memory by calling free:
    free(system_drive);
}

Output:

system drive: C:

Theressathereto

Answer 5

See Getting System Information on MSDN. It explains how to get system information in depth for the most part. very informative.

Deluna

YOu need to format the answer with code tags and line breaks. – Pavonine