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<H1>beam_lib</H1>
</CENTER>

<H3>MODULE</H3>
<DIV CLASS=REFBODY>
beam_lib
</DIV>

<H3>MODULE SUMMARY</H3>
<DIV CLASS=REFBODY>
An Interface To the BEAM File Format
</DIV>

<H3>DESCRIPTION</H3>
<DIV CLASS=REFBODY>

<P><CODE>beam_lib</CODE> provides an interface to files created by
the BEAM compiler (&#34;BEAM files&#34;). The format used, a variant of
&#34;EA IFF 1985&#34; Standard for Interchange Format Files, divides data
into chunks.
<P>Chunk data can be returned as binaries or as compound terms.
Compound terms are returned when chunks are referenced by names
(atoms) rather than identifiers (strings). The names recognized
and the corresponding identifiers are:
<P>
<UL>

<LI>
<CODE>abstract_code (&#34;Abst&#34;)</CODE>
</LI>


<LI>
<CODE>attributes (&#34;Attr&#34;)</CODE>
</LI>


<LI>
<CODE>compile_info (&#34;CInf&#34;)</CODE>
</LI>


<LI>
<CODE>exports (&#34;ExpT&#34;)</CODE>
</LI>


<LI>
<CODE>labeled_exports (&#34;ExpT&#34;)</CODE>
</LI>


<LI>
<CODE>imports (&#34;ImpT&#34;)</CODE>
</LI>


<LI>
<CODE>indexed_imports (&#34;ImpT&#34;)</CODE>
</LI>


<LI>
<CODE>locals (&#34;LocT&#34;)</CODE>
</LI>


<LI>
<CODE>labeled_locals (&#34;LocT&#34;)</CODE>
</LI>


<LI>
<CODE>atoms (&#34;Atom&#34;)</CODE>
</LI>


</UL>

</DIV>
<A NAME="debug_info"><!-- Empty --></A>
<H3>Debug Information/Abstract Code</H3>
<DIV CLASS=REFBODY>

<P>The option <CODE>debug_info</CODE> can be given to the compiler (see
<A HREF="javascript:erlhref('../../../../', 'compiler', 'compile.html#debug_info');">compile(3)</A>)
in order to have debug information in the form of abstract code
(see <A HREF="javascript:erlhref('../../../../', 'erts', 'absform.html');">The Abstract Format</A>
in ERTS User's Guide) stored in the <CODE>abstract_code</CODE> chunk.
Tools such as Debugger and Xref require the debug information to
be included.
<P>
<TABLE CELLPADDING=4>
  <TR>
    <TD VALIGN=TOP><IMG ALT="Warning!" SRC="warning.gif"></TD>
    <TD>

<P>Source code can be reconstructed from the debug information.
        Use encrypted debug information (see below) to prevent this.
    </TD>
  </TR>
</TABLE>

<P>The debug information can also be removed from BEAM files
using <A HREF="#strip/1">strip/1</A>,
<A HREF="#strip_files/1">strip_files/1</A> and/or
<A HREF="#strip_release/1">strip_release/1</A>.
<P><STRONG>Reconstructing source code</STRONG>
<P>Here is an example of how to reconstruct source code from
the debug information in a BEAM file <CODE>Beam</CODE>:
<PRE>
      {ok,{_,[{abstract_code,{_,AC}}]}} = beam_lib:chunks(Beam,[abstract_code]).
      io:fwrite(&#34;~s~n&#34;, [erl_prettypr:format(erl_syntax:form_list(AC))]).
    
</PRE>

<P><STRONG>Encrypted debug information</STRONG>
<P>The debug information can be encrypted in order to keep
the source code secret, but still being able to use tools such as
Xref or Debugger. 
<P>To use encrypted debug information, a key must be provided to
the compiler and <CODE>beam_lib</CODE>. The key is given as a string and
it is recommended that it contains at least 32 characters and
that both upper and lower case letters as well as digits and
special characters are used.
<P>

<P>The default type -- and currently the only type -- of crypto
algorithm is <CODE>des3_cbc</CODE>, three rounds of DES. The key string
will be scrambled using <CODE>erlang:md5/1</CODE> to generate
the actual keys used for <CODE>des3_cbc</CODE>.
<P>
<TABLE CELLPADDING=4>
  <TR>
    <TD VALIGN=TOP><IMG ALT="Note!" SRC="note.gif"></TD>
    <TD>

<P>As far as we know when by the time of writing, it is
        infeasible to break <CODE>des3_cbc</CODE> encryption without any
        knowledge of the key. Therefore, as long as the key is kept
        safe and is unguessable, the encrypted debug information
        <STRONG>should</STRONG> be safe from intruders.    </TD>
  </TR>
</TABLE>

<P>There are two ways to provide the key:
<P>
<OL>

<LI>
        Use the compiler option <CODE>{debug_info,Key}</CODE>, see
         <A HREF="javascript:erlhref('../../../../', 'compiler', 'compile.html#debug_info_key');">compile(3)</A>,
         and the function
         <A HREF="#crypto_key_fun/1">crypto_key_fun/1</A>
         to register a fun which returns the key whenever
         <CODE>beam_lib</CODE> needs to decrypt the debug information.<BR>


        If no such fun is registered, <CODE>beam_lib</CODE> will instead
         search for a <CODE>.erlang.crypt</CODE> file, see below.<BR>


</LI>


<LI>
        Store the key in a text file named <CODE>.erlang.crypt</CODE>.<BR>


        In this case, the compiler option <CODE>encrypt_debug_info</CODE>
         can be used, see
         <A HREF="javascript:erlhref('../../../../', 'compiler', 'compile.html#encrypt_debug_info');">compile(3)</A>.<BR>


</LI>


</OL>

<P><STRONG>.erlang.crypt</STRONG>
<P><CODE>beam_lib</CODE> searches for <CODE>.erlang.crypt</CODE> in the current
directory and then the home directory for the current user. If
the file is found and contains a key, <CODE>beam_lib</CODE> will
implicitly create a crypto key fun and register it.
<P>The <CODE>.erlang.crypt</CODE> file should contain a single list of
tuples:
<PRE>
      {debug_info, Mode, Module, Key}
    
</PRE>

<P><CODE>Mode</CODE> is the type of crypto algorithm; currently, the only
allowed value thus is <CODE>des3_cbc</CODE>. <CODE>Module</CODE> is either an
atom, in which case <CODE>Key</CODE> will only be used for the module
<CODE>Module</CODE>, or <CODE>[]</CODE>, in which case <CODE>Key</CODE> will be
used for all modules. <CODE>Key</CODE> is the non-empty key string.
<P>The <CODE>Key</CODE> in the first tuple where both <CODE>Mode</CODE> and
<CODE>Module</CODE> matches will be used.
<P>Here is an example of an <CODE>.erlang.crypt</CODE> file that returns
the same key for all modules:
<PRE>
[{debug_info, des3_cbc, [], &#34;%&#62;7}|pc/DM6Cga*68$Mw]L#&#38;_Gejr]G^&#34;}].
    
</PRE>

<P>And here is a slightly more complicated example of an
<CODE>.erlang.crypt</CODE> which provides one key for the module
<CODE>t</CODE>, and another key for all other modules:
<PRE>
[{debug_info, des3_cbc, t, &#34;My KEY&#34;},
 {debug_info, des3_cbc, [], &#34;%&#62;7}|pc/DM6Cga*68$Mw]L#&#38;_Gejr]G^&#34;}].
    
</PRE>

<P>
<TABLE CELLPADDING=4>
  <TR>
    <TD VALIGN=TOP><IMG ALT="Note!" SRC="note.gif"></TD>
    <TD>

<P>Do not use any of the keys in these examples. Use your own
        keys.    </TD>
  </TR>
</TABLE>

</DIV>

<H3>DATA TYPES</H3>
<DIV CLASS=REFBODY>

<PRE>
beam() -&#62; Module | Filename | binary()
  Module = atom()
  Filename = string() | atom()
    
</PRE>

<P>Each of the functions described below accept either the module
name, the filename, or a binary containing the beam module.
<PRE>
chunkdata() = {ChunkId, DataB} | {ChunkName, DataT}
  ChunkId = chunkid()
  DataB = binary()
  {ChunkName, DataT} =
        {abstract_code, AbstractCode}
      | {attributes, [{Attribute, [AttributeValue]}]}
      | {compile_info, [{InfoKey, [InfoValue]}]}
      | {exports, [{Function, Arity}]}
      | {labeled_exports, [{Function, Arity, Label}]}
      | {imports, [{Module, Function, Arity}]}
      | {indexed_imports, [{Index, Module, Function, Arity}]}
      | {locals, [{Function, Arity}]}]}
      | {labeled_locals, [{Function, Arity, Label}]}]}
      | {atoms, [{integer(), atom()}]}
  AbstractCode = {AbstVersion, Forms} | no_abstract_code
    AbstVersion = atom()
  Attribute = atom()
  AttributeValue = term()
  Module = Function = atom()
  Arity = int()
  Label = int()
    
</PRE>

<P>It is not checked that the forms conform to the abstract format
indicated by <CODE>AbstVersion</CODE>. <CODE>no_abstract_code</CODE> means
that the <CODE>&#34;Abst&#34;</CODE> chunk is present, but empty.
<P>The list of attributes is sorted on <CODE>Attribute</CODE>, and each
attribute name occurs once in the list. The attribute values
occur in the same order as in the file. The lists of functions
are also sorted.
<PRE>
chunkid() = &#34;Abst&#34; | &#34;Attr&#34; | &#34;CInf&#34;
            | &#34;ExpT&#34; | &#34;ImpT&#34; | &#34;LocT&#34;
            | &#34;Atom&#34;

chunkname() = abstract_code | attributes | compile_info
            | exports | labeled_exports
            | imports | indexed_imports
            | locals | labeled_locals
            | atoms
      
chunkref() = chunkname() | chunkid()
    
</PRE>

</DIV>

<H3>EXPORTS</H3>

<P><A NAME="chunks/2"><STRONG><CODE>chunks(Beam, [ChunkRef]) -&#62; 
        {ok, {Module, [ChunkData]}} | {error, beam_lib, Reason}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Beam = beam()</CODE></STRONG><BR>
<STRONG><CODE>ChunkRef = chunkref()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>ChunkData = chunkdata()</CODE></STRONG><BR>
<STRONG><CODE>Reason = {unknown_chunk, Filename, atom()}</CODE></STRONG><BR>
<STRONG><CODE>| {key_missing_or_invalid, Filename,
         abstract_code}</CODE></STRONG><BR>
<STRONG><CODE>| Reason1 -- see info/1</CODE></STRONG><BR>
<STRONG><CODE>Filename = string()</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Reads chunk data for selected chunks refs. The order of
         the returned list of chunk data is determined by the order
         of the list of chunks references.
</DIV>

<P><A NAME="version/1"><STRONG><CODE>version(Beam) -&#62;
        {ok, {Module, [Version]}} | {error, beam_lib, Reason}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Beam = beam()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Version = term()</CODE></STRONG><BR>
<STRONG><CODE>Reason -- see chunks/2</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Returns the module version(s). A version is defined by
         the module attribute <CODE>-vsn(Vsn)</CODE>. If this attribute is
         not specified, the version defaults to the checksum of
         the module. Note that if the version <CODE>Vsn</CODE> is not a list,
         it is made into one, that is <CODE>{ok,{Module,[Vsn]}}</CODE> is
         returned. If there are several <CODE>-vsn</CODE> module attributes,
         the result is the concatenated list of versions. Examples:
<PRE>
1&#62; <STRONG>beam_lib:version(a).</STRONG> % -vsn(1).
{ok,{a,[1]}}
2&#62; <STRONG>beam_lib:version(b).</STRONG> % -vsn([1]).
{ok,{b,[1]}}
3&#62; <STRONG>beam_lib:version(c).</STRONG> % -vsn([1]). -vsn(2).
{ok,{c,[1,2]}}
4&#62; <STRONG>beam_lib:version(d).</STRONG> % no -vsn attribute
{ok,{d,[275613208176997377698094100858909383631]}}
        
</PRE>

</DIV>

<P><A NAME="info/1"><STRONG><CODE>info(Beam) -&#62; [{Item, Info}] | {error, beam_lib, Reason1}
</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Beam = beam()</CODE></STRONG><BR>
<STRONG><CODE>Item, Info -- see below</CODE></STRONG><BR>
<STRONG><CODE>Reason1 =
         {chunk_too_big, Filename, ChunkId, ChunkSize, FileSize}</CODE></STRONG><BR>
<STRONG><CODE>| {invalid_beam_file, Filename, Pos}</CODE></STRONG><BR>
<STRONG><CODE>| {invalid_chunk, Filename, ChunkId}</CODE></STRONG><BR>
<STRONG><CODE>| {missing_chunk, Filename, ChunkId}</CODE></STRONG><BR>
<STRONG><CODE>| {not_a_beam_file, Filename}</CODE></STRONG><BR>
<STRONG><CODE>| {file_error, Filename, Posix}</CODE></STRONG><BR>
<STRONG><CODE>Filename = string()</CODE></STRONG><BR>
<STRONG><CODE>ChunkId = chunkid()</CODE></STRONG><BR>
<STRONG><CODE>ChunkSize = FileSize = int()</CODE></STRONG><BR>
<STRONG><CODE>Pos = int()</CODE></STRONG><BR>
<STRONG><CODE>Posix = posix() -- see file(3)</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Returns a list containing some information about a BEAM file
         as tuples <CODE>{Item, Info}</CODE>:
<P>
<DL>

<DT>
<CODE>{file, Filename} | {binary, Binary}</CODE>
</DT>

<DD>
         The name (string) of the BEAM file, or the binary from
         which the information was extracted.<BR>

         
</DD>

<DT>
<CODE>{module, Module}</CODE>
</DT>

<DD>
         The name (atom) of the module.<BR>

         
</DD>

<DT>
<CODE>{chunks, [{ChunkId, Pos, Size}]}</CODE>
</DT>

<DD>
         For each chunk, the identifier (string) and the position
         and size of the chunk data, in bytes.<BR>

         
</DD>

</DL>

</DIV>

<P><A NAME="cmp/2"><STRONG><CODE>cmp(Beam1, Beam2) -&#62; ok | {error, beam_lib, Reason}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Beam1 = Beam2 = beam()</CODE></STRONG><BR>
<STRONG><CODE>Reason = {modules_different, Module1, Module2}</CODE></STRONG><BR>
<STRONG><CODE>| {chunks_different, ChunkId}</CODE></STRONG><BR>
<STRONG><CODE>| Reason1 -- see info/1</CODE></STRONG><BR>
<STRONG><CODE>Module1 = Module2 = atom()</CODE></STRONG><BR>
<STRONG><CODE>ChunkId = chunkid()</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Compares the contents of two BEAM files. If the module names
         are the same, and the chunks with the identifiers
         <CODE>&#34;Code&#34;</CODE>, <CODE>&#34;ExpT&#34;</CODE>, <CODE>&#34;ImpT&#34;</CODE>, <CODE>&#34;StrT&#34;</CODE>,
         and <CODE>&#34;Atom&#34;</CODE> have the same contents in both files,
         <CODE>ok</CODE> is returned. Otherwise an error message is returned.
        
</DIV>

<P><A NAME="cmp_dirs/2"><STRONG><CODE>cmp_dirs(Dir1, Dir2) -&#62; 
        {Only1, Only2, Different} | {error, beam_lib, Reason1}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Dir1 = Dir2 = string() | atom()</CODE></STRONG><BR>
<STRONG><CODE>Different = [{Filename1, Filename2}]</CODE></STRONG><BR>
<STRONG><CODE>Only1 = Only2 = [Filename]</CODE></STRONG><BR>
<STRONG><CODE>Filename = Filename1 = Filename2 = string()</CODE></STRONG><BR>
<STRONG><CODE>Reason1 -- see info/1</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>The <CODE>cmp_dirs/2</CODE> function compares the BEAM files in
         two directories. Only files with extension <CODE>&#34;.beam&#34;</CODE> are
         compared. BEAM files that exist in directory <CODE>Dir1</CODE>
         (<CODE>Dir2</CODE>) only are returned in <CODE>Only1</CODE>
         (<CODE>Only2</CODE>). BEAM files that exist on both directories but
         are considered different by <CODE>cmp/2</CODE> are returned as
         pairs {<CODE>Filename1</CODE>, <CODE>Filename2</CODE>} where
         <CODE>Filename1</CODE> (<CODE>Filename2</CODE>) exists in directory
         <CODE>Dir1</CODE> (<CODE>Dir2</CODE>).
</DIV>

<P><A NAME="diff_dirs/2"><STRONG><CODE>diff_dirs(Dir1, Dir2) -&#62; ok | {error, beam_lib, Reason1}
</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Dir1 = Dir2 = string() | atom()</CODE></STRONG><BR>
<STRONG><CODE>Reason1 -- see info/1</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>The <CODE>diff_dirs/2</CODE> function compares the BEAM files in
         two directories the way <CODE>cmp_dirs/2</CODE> does, but names of
         files that exist in only one directory or are different are
         presented on standard output.
</DIV>

<P><A NAME="strip/1"><STRONG><CODE>strip(Beam1) -&#62;
        {ok, {Module, Beam2}} | {error, beam_lib, Reason1}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Beam1 = Beam2 = beam()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Reason1 -- see info/1</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>The <CODE>strip/1</CODE> function removes all chunks from a BEAM
         file except those needed by the loader. In particular,
         the debug information (<CODE>abstract_code</CODE> chunk) is removed.
        
</DIV>

<P><A NAME="strip_files/1"><STRONG><CODE>strip_files(Files) -&#62; 
{ok, [{Module, Beam2}]} | {error, beam_lib, Reason1}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Files = [Beam1]</CODE></STRONG><BR>
<STRONG><CODE>Beam1 = beam()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Beam2 = beam()</CODE></STRONG><BR>
<STRONG><CODE>Reason1 -- see info/1</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>The <CODE>strip_files/1</CODE> function removes all chunks except
         those needed by the loader from BEAM files. In particular,
         the debug information (<CODE>abstract_code</CODE> chunk) is removed.
         The returned list contains one element for each given file
         name, in the same order as in <CODE>Files</CODE>.
</DIV>

<P><A NAME="strip_release/1"><STRONG><CODE>strip_release(Dir) -&#62; 
{ok, [{Module, Filename]}} | {error, beam_lib, Reason1}
</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Dir = string() | atom()</CODE></STRONG><BR>
<STRONG><CODE>Module = atom()</CODE></STRONG><BR>
<STRONG><CODE>Filename = string()</CODE></STRONG><BR>
<STRONG><CODE>Reason1 -- see info/1</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>The <CODE>strip_release/1</CODE> function removes all chunks
         except those needed by the loader from the BEAM files of a
         release. <CODE>Dir</CODE> should be the installation root
         directory. For example, the current OTP release can be
         stripped with the call
         <CODE>beam_lib:strip_release(code:root_dir())</CODE>.
</DIV>

<P><A NAME="format_error/1"><STRONG><CODE>format_error(Reason) -&#62; Chars</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Reason -- see other functions</CODE></STRONG><BR>
<STRONG><CODE>Chars = [char() | Chars]</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Given the error returned by any function in this module, 
         the function <CODE>format_error</CODE> returns a descriptive string
         of the error in English. For file errors, the function 
         <CODE>file:format_error(Posix)</CODE> should be called.
</DIV>

<P><A NAME="crypto_key_fun/1"><STRONG><CODE>crypto_key_fun(CryptoKeyFun) -&#62; ok | {error, Reason}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>CryptoKeyFun = fun() -- see below</CODE></STRONG><BR>
<STRONG><CODE>Reason = badfun | exists | term()</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>The <CODE>crypto_key_fun/1</CODE> function registers a unary fun
         that will be called if <CODE>beam_lib</CODE> needs to read an
         <CODE>abstract_code</CODE> chunk that has been encrypted. The fun
         is held in a process that is started by the function.
<P>If there already is a fun registered when attempting to
         register a fun, <CODE>{error, exists}</CODE> is returned.
<P>The fun must handle the following arguments:
<PRE>
          CryptoKeyFun(init) -&#62; ok | {ok, NewCryptoKeyFun} | {error, Term}
        
</PRE>

<P>Called when the fun is registered, in the process that holds
         the fun. Here the crypto key fun can do any necessary
         initializations. If <CODE>{ok, NewCryptoKeyFun}</CODE> is returned
         then <CODE>NewCryptoKeyFun</CODE> will be registered instead of
         <CODE>CryptoKeyFun</CODE>. If <CODE>{error, Term}</CODE> is returned,
         the registration is aborted and <CODE>crypto_key_fun/1</CODE>
         returns <CODE>{error, Term}</CODE> as well.
<PRE>
          CryptoKeyFun({debug_info, Mode, Module, Filename}) -&#62; Key
        
</PRE>

<P>Called when the key is needed for the module <CODE>Module</CODE>
         in the file named <CODE>Filename</CODE>. <CODE>Mode</CODE> is the type of
         crypto algorithm; currently, the only possible value thus is
         <CODE>des3_cbc</CODE>. The call should fail (raise an exception) if
         there is no key available.
<PRE>
          CryptoKeyFun(clear) -&#62; term()
        
</PRE>

<P>Called before the fun is unregistered. Here any cleaning up
         can be done. The return value is not important, but is passed
         back to the caller of <CODE>clear_crypto_key_fun/0</CODE> as part
         of its return value.
</DIV>

<P><A NAME="clear_crypto_key_fun/0"><STRONG><CODE>clear_crypto_key_fun() -&#62; {ok, Result}</CODE></STRONG></A><BR>

<DIV CLASS=REFBODY><P>Types:
  <DIV CLASS=REFTYPES>
<P>
<STRONG><CODE>Result = undefined | term()</CODE></STRONG><BR>

  </DIV>
</DIV>

<DIV CLASS=REFBODY>

<P>Unregisters the crypto key fun and terminates the process
         holding it, started by <CODE>crypto_key_fun/1</CODE>.
<P>The <CODE>clear_crypto_key_fun/1</CODE> either returns
         <CODE>{ok, undefined}</CODE> if there was no crypto key fun
         registered, or <CODE>{ok, Term}</CODE>, where <CODE>Term</CODE> is
         the return value from <CODE>CryptoKeyFun(clear)</CODE>, see
         <CODE>crypto_key_fun/1</CODE>.
</DIV>

<H3>AUTHORS</H3>
<DIV CLASS=REFBODY>
Hans Bolinder - support@erlang.ericsson.se<BR>

</DIV>
<CENTER>
<HR>
<SMALL>stdlib 1.14.2<BR>
Copyright &copy; 1991-2006
<A HREF="http://www.erlang.se">Ericsson AB</A><BR>
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