C++: Setenv(). Undefined identifier in Visual Studio

Question

Look my code seems to be correct, according to all the documentation I can find online. My IDE is MS Visual Studio Xpress 4 Windows Desktop 2012, and it\'s compiler is throw

Answer 1

You can either use _putenv() which takes a string parameter as the string classSize=7;

ostringstream classSize;
classSize << "classSize=" << howManyInClass;
_putenv(classSize.str().c_str());

...or (preferably) the security enhanced _putenv_s() that takes the key and the value as separate (const char*) parameters;

ostringstream classSize;
classSize << howManyInClass;
_putenv_s("classSize", classSize.str().c_str());