set variable to cmd.exe

Question

Greeting earthmen,

Here is my question:

How can I create a program which sets variable to current session of cmd.exe eg

c:\> set myvar
Environment variable myvar not defined
c:\>myexe.exe
c:>set myvar
myvar=myvalue

The only similar topic that I've found is this -

How can I change Windows shell (cmd.exe) environment variables from C++?

But I didn't get a single word from this:

There is a way... Just inject your code into parent process and call SetEnvironmentVariableA inside cmd's process memory. After injecting just free the allocated memory.

While C/C++ is not my "native" language I've felt myself completely lost when I've searched google with "c++ inject code" and etc... Is there an article where I can get more info about this.

BTW now I'm using one a little bit stupid workaround.As the setting a variable to

HKEY_CURRENT_USER\\Environment

and

HKEY_LOCAL_MACHINE\\SYSTEM\\CurrentControlSet\\Control\\Session Manager\\Environment

is comparatively easy I'm just recording similar variable to the registry:

load.temp.vars=set myvar1=myval1&set myvar2=myval2& ....

and then just call %load.temp.vars% and it will be executed as a command:

c:/>%load.temp.vars%
c:/>set myvar1
myvar1=myval1

It works fine bu it's not good enough for me :)

Live long and prosper, \\\\//_

Answer 1

Check out this article: Three Ways to Inject Your Code into Another Process .

Also you probably will need a handle to your parent process (to determine the target process whose environment to change). A way to get it is described here .

Just keep in mind that injection may not work, depending on user account privileges, and also that some especially paranoid antivirus solutions may frown upon it.

Answer 2

There are very easy way to do this without any tricks .

You should write a small program myexe.exe which produce a simple output (console output) like following:

SET myvar=Some value

then you start your program with the following steps:

myexe.exe >%TEMP%\t.cmd
call %TEMP%\t.cmd
del %TEMP%\t.cmd

Now in the current cmd.exe which started myexe.exe exist the environment variable myvar and it has the value Some value . Is it not exactly what you want?

The way is extrem simple and it works on all versions of Windows (and not only Windows). So it is my recommendation for you.