JSON_HAS_FILESYSTEM / JSON_HAS_EXPERIMENTAL_FILESYSTEM

#define JSON_HAS_FILESYSTEM /* value */
#define JSON_HAS_EXPERIMENTAL_FILESYSTEM /* value */

When compiling with C++17, the library provides conversions from and to std::filesystem::path. As compiler support for filesystem is limited, the library tries to detect whether <filesystem>/std::filesystem (JSON_HAS_FILESYSTEM) or <experimental/filesystem>/std::experimental::filesystem (JSON_HAS_EXPERIMENTAL_FILESYSTEM) should be used. To override the built-in check, define JSON_HAS_FILESYSTEM or JSON_HAS_EXPERIMENTAL_FILESYSTEM to 1.

Default definition

The default value is detected based on the preprocessor macros #!cpp __cpp_lib_filesystem, #!cpp __cpp_lib_experimental_filesystem, #!cpp __has_include(<filesystem>), or #!cpp __has_include(<experimental/filesystem>).

Notes

• Note that older compilers or older versions of libstd++ also require the library stdc++fs to be linked to for filesystem support.
• Both macros are undefined outside the library.

Examples

??? example

The code below forces the library to use the header `<experimental/filesystem>`.

```cpp
#define JSON_HAS_EXPERIMENTAL_FILESYSTEM 1
#include <nlohmann/json.hpp>

...
```

Version history

• Added in version 3.10.5.