How to open a folder in %appdata% with C++?

As yo开发者_如何学编程u all know, the appdata folder is this

 C:\Users\*Username*\AppData\Roaming

on windows 7

Since my application will be deployed on all kinds of Windows OSes i need to be able to get the folder 100% percent of the time. The question is how do you do it in C++? Since i don't know the the exact Windows OS it could be XP,Vista or 7 and most importantly i don't know what the Username is.

For maximum compatibility with all versions of Windows, you can use the SHGetFolderPath function.
It requires that you specify the CSIDL value for the folder whose path you want to retrieve. For the application data folder, that would be CSIDL_APPDATA.

On Windows Vista and later, you should use the SHGetKnownFolderPath function instead, which requires that you specify the folder's KNOWNFOLDERID value. Again, for the application data folder, the appropriate value is FOLDERID_RoamingAppData.

To use either of these functions from your C++ application, you'll need to include shlobj.h.

You can try the following:

char* appdata = getenv("APPDATA");

This code reads the environment variable APPDATA (you can also see it when you type SET in a command window). It is set by Windows when your system starts.

It will return the path of the user's appdata as an absolute path, including Username and taking into account whichever OS version they're using.

Perhaps fellow Googlers might find it interesting to have a look at std::filesystem. For instance, let's assume the default temp directory location and AppData directory structure in Windows 10:

#include <filesystem>

auto path = std::filesystem::temp_directory_path()
    .parent_path()
    .parent_path();

path /= "Roaming";

if (!std::filesystem::exists(path))
    std::filesystem::create_directories(path);

In the case of OP, I am assuming this doesn't solve the problem. I do want to raise a word of caution against doing the above in a situation that requires a 100% robust implementation, as system configurations can easily change and break the above.

But perhaps new visitors to the question might find std::filesystem useful. Chances are, you're going to want to manipulate the items in the directory if you're looking for it, and for this, std::filesystem can be your friend.

If someone is looking for a simple implementation, here's mine:

#include <windows.h>
#include <shlobj.h>

#include <filesystem>
#include <iostream>

int main(void)
{
    std::filesystem::path path;
    PWSTR path_tmp;

    /* Attempt to get user's AppData folder
     *
     * Microsoft Docs:
     * https://learn.microsoft.com/en-us/windows/win32/api/shlobj_core/nf-shlobj_core-shgetknownfolderpath
     * https://learn.microsoft.com/en-us/windows/win32/shell/knownfolderid
     */
    auto get_folder_path_ret = SHGetKnownFolderPath(FOLDERID_RoamingAppData, 0, nullptr, &path_tmp);

    /* Error check */
    if (get_folder_path_ret != S_OK) {
        CoTaskMemFree(path_tmp);
        return 1;
    }

    /* Convert the Windows path type to a C++ path */
    path = path_tmp;

    /* Free memory :) */
    CoTaskMemFree(path_tmp);

    std::cout << path << std::endl;

    return 0;
}

Use this Code to reads the environment variable "APPDATA"
Include stdio.h file in beginning

char *pValue;
size_t len;
errno_t err = _dupenv_s(&pValue, &len, "APPDATA");

Here is a simple implementation for old C++ versions :

#include <shlobj.h>
// ...
wchar_t* localAppDataFolder;
if (SHGetKnownFolderPath(FOLDERID_LocalAppData, KF_FLAG_CREATE, NULL, &localAppDataFolder) != S_OK) {
    std::cerr << "problem getting appdata folder" << std::endl;
}
else std::wcout << L"folder found: " << localAppDataFolder << std::endl;