apt-get environment variables when spawning "debian rules" file

Question

What are the environment variables made available to debian/rules (often make) when spawned by apt-get during installation of a package under Ubuntu?

I am specifically after the environment variables that would pertain to Gnome's configuration directories. I'd like avoiding "hardcoding" things like ~/.conf/apps/ ... since I have been told these might change like they tend to...

I've been googling like crazy!

Answer 1

debian/rules gets invoked at package build time (either the source or binary package) It does not get called during apt-get.

In fact, the .deb file (==binary package), does not contain a copy of debian/rules anymore. That file is only in the source package.

Furthermore, packages should normally not try to do things for a particular user, or make use of the configuration of a user. Debian packages are intended for software that is installed system-wide.

Although it's theoretically possible to make a personal package that installs something in /home, such a package is of very limited value.

Answer 2

Are you looking for the XDG_CONFIG_HOME and related? In particular, note that XDG_CONFIG_HOME doesn't have to exist, and a value of ~/.config is assumed in that case.

Python example

import os
from os import path

app_name = "my_app"
home_config = path.join(
  os.environ.get("XDG_CONFIG_HOME") or path.expanduser("~/.config"),
  app_name,
)

print "User-specific config:", home_config

C++ example

#include <cstdlib>
#include <iostream>
#include <stdexcept>
#include <string>

std::string get_home_config(std::string const& app_name) {
  // also look at boost's filesystem library
  using namespace std;
  string home_config;
  char const* xdg_config_home = getenv("XDG_CONFIG_HOME");
  if (xdg_config_home && xdg_config_home[0] != '\0') {
    home_config = xdg_config_home;
  }
  else {
    if (char const* home = getenv("HOME")) {
      home_config = home;
      home_config += "/.config";
    }
    else throw std::runtime_error("HOME not set");
  }
  home_config += "/";
  home_config += app_name;
  return home_config;
}

int main() try {
  std::cout << "User-specific config: " << get_home_config("my_app") << '\n';
  return 0;
}
catch (std::exception& e) {
  std::clog << e.what() << std::endl;
  return 1;
}