5.4 module_info/0 and module_info/1 functions

The compiler automatically inserts the two special, exported functions into each module:

  • Module:module_info/0
  • Module:module_info/1These functions can be called to retrieve information about the module.

module_info/0

The module_info/0 function in each module, returns a list of {Key,Value} tuples with information about the module. Currently, the list contain tuples with the following Keys: module, attributes, compile, exports, md5 and native. The order and number of tuples may change without prior notice.

module_info/1

The call module_info(Key), where Key is an atom, returns a single piece of information about the module.

The following values are allowed for Key:

  • module

  • Returns an atom representing the module name.

  • attributes

  • Returns a list of {AttributeName,ValueList} tuples, where AttributeName is the name of an attribute, and ValueList is a list of values. Notice that a given attribute can occur more than once in the list with different values if the attribute occurs more than once in the module.

The list of attributes becomes empty if the module is stripped with the beam_lib(3) module (in STDLIB).

  • compile

  • Returns a list of tuples with information about how the module was compiled. This list is empty if the module has been stripped with the beam_lib(3) module (in STDLIB).

  • md5

  • Returns a binary representing the MD5 checksum of the module. If the module has native code loaded, this will be the MD5 of the native code, not the BEAM bytecode.

  • exports

  • Returns a list of {Name,Arity} tuples with all exported functions in the module.

  • functions

  • Returns a list of {Name,Arity} tuples with all functions in the module.

  • nifs

  • Returns a list of {Name,Arity} tuples with all NIF functions in the module.

  • native

  • Return true if the module has native compiled code. Return false otherwise. In a system compiled without HiPE support, the result is always false