Function GetEnvVar

cpp/src/arrow/util/io_util.cc:1762–1791

//

Result<std::string> GetEnvVar(std::string_view name) {
#ifdef _WIN32
  // On Windows, getenv() reads an early copy of the process' environment
  // which doesn't get updated when SetEnvironmentVariable() is called.
  std::string value(100, '\0');

  uint32_t res = GetEnvironmentVariableA(name.data(), value.data(),
                                         static_cast<uint32_t>(value.size()));
  if (res >= value.size()) {
    // Value buffer too small, need to upsize
    // (`res` includes the null-terminating character in this case)
    value.resize(res);
    res = GetEnvironmentVariableA(name.data(), value.data(),
                                  static_cast<uint32_t>(value.size()));
  }
  if (res == 0) {
    return Status::KeyError("environment variable '", name, "' undefined");
  }
  // On success, `res` does not include the null-terminating character
  DCHECK_EQ(value.data()[res], 0);
  value.resize(res);
  return value;
#else
  char* c_str = getenv(name.data());
  if (c_str == nullptr) {
    return Status::KeyError("environment variable '", name, "' undefined");
  }
  return std::string(c_str);
#endif
}

#ifdef _WIN32
Result<NativePathString> GetEnvVarNative(std::string_view name) {