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Niels Lohmann 29cd970b94 Consolidate documentation (#3071) 
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operator<<(basic_json)

std::ostream& operator<<(std::ostream& o, const basic_json& j);

Serialize the given JSON value j to the output stream o. The JSON value will be serialized using the dump member function.

  • The indentation of the output can be controlled with the member variable width of the output stream o. For instance, using the manipulator std::setw(4) on o sets the indentation level to 4 and the serialization result is the same as calling dump(4).
  • The indentation character can be controlled with the member variable fill of the output stream o. For instance, the manipulator std::setfill('\\t') sets indentation to use a tab character rather than the default space character.

Parameters

o (in, out)
stream to serialize to
j (in)
JSON value to serialize

Return value

the stream o

Exceptions

Throws type_error.316 if a string stored inside the JSON value is not UTF-8 encoded. Note that unlike the dump member functions, no error_handler can be set.

Complexity

Linear.

Examples

??? example

The example below shows the serialization with different parameters to `width` to adjust the indentation level.
    
```cpp
--8<-- "examples/operator_serialize.cpp"
```

Output:

```json
--8<-- "examples/operator_serialize.output"
```

Version history

  • Added in version 1.0.0
  • Support for indentation character added in version 3.0.0.

!!! warning "Deprecation"

This function replaces function `#!cpp std::ostream& operator>>(const basic_json& j, std::ostream& o)` which has
been deprecated in version 3.0.0. It will be removed in version 4.0.0. Please replace calls like `#!cpp j >> o;`
with `#!cpp o << j;`.