find config from env

README.md

@@ -158,6 +158,13 @@ Document 文檔: https://byvoid.github.io/OpenCC/
 * `jp2t.json` New Japanese Kanji (Shinjitai) to Traditional Chinese Characters (Kyūjitai) 日文新字體到繁體（OpenCC 標準，舊字體）
 * `tw2t.json` Traditional Chinese (Taiwan standard) to Traditional Chinese 臺灣正體到繁體（OpenCC 標準）
 
+#### 指定配置文件
+
+通过环境变量`OPENCC_DATA_DIR`加载指定路径下的配置文件
+```sh
+OPENCC_DATA_DIR=/path/to/your/config/dir opencc --help
+```
+
 ## Build 編譯
 
 ### Build with CMake

src/Config.cpp

@@ -202,6 +202,15 @@ class ConfigInternal {
       }
     }
 
+    const char* envPath = std::getenv("OPENCC_DATA_DIR");
+    if (envPath != nullptr) {
+      auto path = std::string(envPath) + '/' + fileName;
+      ifs.open(UTF8Util::GetPlatformString(path).c_str());
+      if (ifs.is_open()) {
+        return path;
+      }
+    }
+
     throw FileNotFound(fileName);
   }
 };