Function GetOSReleaseVariables

Source/cmCMakeHostSystemInformationCommand.cxx:328–441

}

std::map<std::string, std::string> GetOSReleaseVariables(
  cmExecutionStatus& status)
{
  auto& makefile = status.GetMakefile();
  auto const& sysroot = makefile.GetSafeDefinition("CMAKE_SYSROOT");

  std::map<std::string, std::string> data;
  // Based on
  // https://www.freedesktop.org/software/systemd/man/latest/os-release.html
  for (auto name : { "/etc/os-release"_s, "/usr/lib/os-release"_s }) {
    auto const& filename = cmStrCat(sysroot, name);
    if (cmSystemTools::FileExists(filename)) {
      cmsys::ifstream fin(filename.c_str());
      for (std::string line; !std::getline(fin, line).fail();) {
        auto kv = ParseOSReleaseLine(line);
        if (kv.has_value()) {
          data.emplace(kv.value());
        }
      }
      break;
    }
  }
  // Got smth?
  if (!data.empty()) {
    return data;
  }

  // Ugh, it could be some pre-os-release distro.
  // Lets try some fallback getters.
  // See also:
  //  - http://linuxmafia.com/faq/Admin/release-files.html

  // 1. CMake provided
  cmsys::Glob gl;
  std::vector<std::string> scripts;
  auto const findExpr = cmStrCat(cmSystemTools::GetCMakeRoot(),
                                 "/Modules/Internal/OSRelease/*.cmake");
  if (gl.FindFiles(findExpr)) {
    scripts = gl.GetFiles();
  }

  // 2. User provided (append to the CMake provided)
  cmList::append(
    scripts, makefile.GetDefinition("CMAKE_GET_OS_RELEASE_FALLBACK_SCRIPTS"));

  // Filter out files that are not in format `NNN-name.cmake`
  auto checkName = [](std::string const& filepath) -> bool {
    auto const& filename = cmSystemTools::GetFilenameName(filepath);
    // NOTE Minimum filename length expected:
    //   NNN-<at-least-one-char-name>.cmake  --> 11
    return (filename.size() < 11) || !cmsysString_isdigit(filename[0]) ||
      !cmsysString_isdigit(filename[1]) || !cmsysString_isdigit(filename[2]) ||
      filename[3] != '-';
  };
  scripts.erase(std::remove_if(scripts.begin(), scripts.end(), checkName),
                scripts.end());

  // Make sure scripts are running in desired order