---
name: "xmerl"
section: "3erl"
platform: "linux"
package: "erlang-manpages"
version: "1:25.2.3+dfsg-1+deb12u4"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/xmerl"
---

# xmerl(3erl)

Functions for exporting XML data to an external format.

## NAME

xmerl - Functions for exporting XML data to an external format.

## DESCRIPTION

Functions for exporting XML data to an external format.

## EXPORTS

**callbacks(Module) -\> Result**\

Types:

Module = atom()\
 Result = \[atom()\]\

Find the list of inherited callback modules for a given module.

**export(Content, Callback) -\> ExportedFormat**\

Equivalent to export(Data, Callback, \[\]).

**export(Content, Callback, RootAttributes) -\> ExportedFormat**\

Types:

Content = \[Element\]\
 Callback = atom()\
 RootAttributes = \[XmlAttributes\]\

Exports normal, well-formed XML content, using the specified callback-module.

*Element* is any of:

- \*

  *#xmlText{}*

- \*

  *#xmlElement{}*

- \*

  *#xmlPI{}*

- \*

  *#xmlComment{}*

- \*

  *#xmlDecl{}*

(See *xmerl.hrl* for the record definitions.) Text in *#xmlText{}* elements can be deep lists of characters and/or binaries.

*RootAttributes* is a list of *#xmlAttribute{}* attributes for the *#root#* element, which implicitly becomes the parent of the given *Content*. The tag-handler function for *#root#* is thus called with the complete exported data of *Content*. Root attributes can be used to specify e.g. encoding or other metadata of an XML or HTML document.

The *Callback* module should contain hook functions for all tags present in the data structure. A hook function must have the following format:

```
    Tag(Data, Attributes, Parents, E)
```

where *E* is the corresponding *#xmlElement{}*, *Data* is the already-exported contents of *E* and *Attributes* is the list of *#xmlAttribute{}* records of *E*. Finally, *Parents* is the list of parent nodes of *E*, on the form *\[{ParentTag::atom(), ParentPosition::integer()}\]*.

The hook function should return either the data to be exported, or a tuple *{'#xml-alias#', NewTag::atom()}*, or a tuple *{'#xml-redefine#', Content}*, where *Content* is a content list (which can be on simple-form; see *export\_simple/2* for details).

A callback module can inherit definitions from other callback modules, through the required function *'#xml-interitance#() -\> \[ModuleName::atom()\]*.

*See also:* export/2, export\_simple/3.

**export\_content(Es::Content, Callbacks) -\> term()**\

Types:

Content = \[Element\]\
 Callback = \[atom()\]\

Exports normal XML content directly, without further context.

**export\_element(E, CB) -\> term()** \

Exports a normal XML element directly, without further context.

**export\_element(E, CallbackModule, CallbackState) -\> ExportedFormat**\

For on-the-fly exporting during parsing (SAX style) of the XML document.

**export\_simple(Content, Callback) -\> ExportedFormat**\

Equivalent to export\_simple(Content, Callback, \[\]).

**export\_simple(Content, Callback, RootAttrs::RootAttributes) -\> ExportedFormat**\

Types:

Content = \[Element\]\
 Callback = atom()\
 RootAttributes = \[XmlAttributes\]\

Exports "simple-form" XML content, using the specified callback-module.

*Element* is any of:

- \*

  *{Tag, Attributes, Content}*

- \*

  *{Tag, Content}*

- \*

  *Tag*

- \*

  *IOString*

- \*

  *#xmlText{}*

- \*

  *#xmlElement{}*

- \*

  *#xmlPI{}*

- \*

  *#xmlComment{}*

- \*

  *#xmlDecl{}*

where

- \*

  *Tag = atom()*

- \*

  *Attributes = \[{Name, Value}\]*

- \*

  *Name = atom()*

- \*

  *Value = IOString \| atom() \| integer()*

Normal-form XML elements can thus be included in the simple-form representation. Note that content lists must be flat. An *IOString* is a (possibly deep) list of characters and/or binaries.

*RootAttributes* is a list of:

- \*

  *XmlAttributes = #xmlAttribute{}*

See *export/3* for details on the callback module and the root attributes. The XML-data is always converted to normal form before being passed to the callback module.

*See also:* export/3, export\_simple/2.

**export\_simple\_content(Content, Callback) -\> term()** \

Exports simple XML content directly, without further context.

**export\_simple\_element(Content, Callback) -\> term()** \

Exports a simple XML element directly, without further context.

## AUTHORS

*\<\>*