---
name: "bson_append_document_begin"
section: "3"
platform: "linux"
package: "libbson-doc"
version: "1.30.4-1+deb13u3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/bson_append_document_begin"
---

# bson\_append\_document\_begin(3)

## SYNOPSIS

```
#define BSON_APPEND_DOCUMENT_BEGIN(b, key, child) \
   bson_append_document_begin (b, key, (int) strlen (key), child)
bool
bson_append_document_begin (bson_t *bson,
                            const char *key,
                            int key_length,
                            bson_t *child);
```

## PARAMETERS

- •

  **bson**: A *bson\_t*.

- •

  **key**: An ASCII C string containing the name of the field.

- •

  **key\_length**: The length of **key** in bytes, or -1 to determine the length with **strlen()**.

- •

  **child**: An uninitialized *bson\_t* to be initialized as the sub-document.

## DESCRIPTION

The *bson\_append\_document\_begin()* function shall begin appending a sub-document to **bson**. Use **child** to add fields to the sub-document. When completed, call *bson\_append\_document\_end()* to complete the element.

**child** *MUST* be an uninitialized *bson\_t* to avoid leaking memory.

## RETURNS

Returns **true** if the operation was applied successfully. The function will fail if **bson** must grow larger than INT32\_MAX.

## AUTHOR

MongoDB, Inc

## COPYRIGHT

2009-present, MongoDB, Inc.