user2264410 user2264410 - 3 months ago 88
C++ Question

Can anyone give me example code of _dupenv_s?

I'm using

getenv("TEMP")
, but I'm getting a warning telling me to use
_dupenv_s
.

I can't find an example of _dupenv_s on the net.

The docs read:

errno_t _dupenv_s(
char **buffer,
size_t *numberOfElements,
const char *varname
);


But what buffer are they referring to? I only have varname. Wouldn't it be better to avoid using a buffer?

Answer

_dupenv_s is a Microsoft function, designed as a more secure form of getenv.

_dupenv_s allocates the buffer itself; you have to pass it a pointer to a pointer and it sets this to the address of the newly allocated buffer.

For example,

char* buf = nullptr;
size_t sz = 0;
if (_dupenv_s(&buf, &sz, "EnvVarName") == 0 && buf != nullptr)
{
    printf("EnvVarName = %s\n", buf);
    free(buf);
}

Note that you're responsible for freeing the returned buffer.