Environment variabile in Macro path

Question

I need to define some path to files with macros. How can I use the $HOME environment variable? I can't find it on the GNU manual, and this doesn't work:

#define LOGMMBOXMAN    "$HOME/mmbox/LOGmmboxman"

Answer 1

No it shouldn't and you probably don't want constant-defined settings like that in any case. If you did that and it worked as you're intending to use it, your home directory would be built in as whatever $HOME is for whoever's doing the building. The executable then depends on that specific home directory existing. If that's OK, just #define your own home. I suspect it isn't though, so you need to deduce it at runtime.

For run-time deduction what you want is this, such that:

const char* home_dir = getenv("HOME");

If there is no $HOME defined, you get NULL returned so be sure to test for this.

You can then build your string based on that. You'll need #include <stdlib.h>.