path: root/lib/erl_interface/doc/src/erl_global.xml

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  <header>
    <copyright>
      <year>1998</year><year>2016</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      Licensed under the Apache License, Version 2.0 (the "License");
      you may not use this file except in compliance with the License.
      You may obtain a copy of the License at

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    </legalnotice>

    <title>erl_global</title>
    <prepared>Gordon Beaton</prepared>
    <responsible>Gordon Beaton</responsible>
    <docno></docno>
    <approved>Gordon Beaton</approved>
    <checked>Gordon Beaton</checked>
    <date>1998-07-03</date>
    <rev>A</rev>
    <file>erl_global.xml</file>
  </header>
  <lib>erl_global</lib>
  <libsummary>Access globally registered names.</libsummary>
  <description>
    <p>This module provides support for registering, looking
      up, and unregistering names in the <c>global</c> module.
      For more information, see
      <seealso marker="kernel:global"><c>kernel:global</c></seealso>.</p>

    <p>Notice that the functions below perform an RPC using an open file
      descriptor provided by the caller. This file descriptor must
      not be used for other traffic during the global operation, as the
      function can then receive unexpected data and fail.</p>
  </description>

  <funcs>
    <func>
      <name since=""><ret>char **</ret><nametext>erl_global_names(fd,count)</nametext></name>
      <fsummary>Obtain list of global names.</fsummary>
      <type>
        <v>int fd;</v>
        <v>int *count;</v>
      </type>
      <desc>
        <p>Retrieves a list of all known global names.</p>
        <list type="bulleted">
          <item><c>fd</c> is an open descriptor to an Erlang
            connection.</item>
          <item><c>count</c> is the address of an integer, or
            <c>NULL</c>. If <c>count</c> is not <c>NULL</c>, it is
            set by the function to the number of names found.</item>
        </list>
        <p>On success, the function returns an array of strings, each
          containing a single registered name, and sets
          <c>count</c> to
          the number of names found. The array is terminated
          by a single <c>NULL</c> pointer. On failure, the function returns
          <c>NULL</c> and <c>count</c> is not modified.</p>
        <note>
          <p>It is the caller's responsibility to free the array
            afterwards. It has been allocated by the function with a
            single call to <c>malloc()</c>, so a single
            <c>free()</c> is all that is necessary.</p>
        </note>
      </desc>
    </func>

    <func>
      <name since=""><ret>int</ret><nametext>erl_global_register(fd,name,pid)</nametext></name>
      <fsummary>Register a name in global.</fsummary>
      <type>
        <v>int fd;</v>
        <v>const char *name;</v>
        <v>ETERM *pid;</v>
      </type>
      <desc>
        <p>Registers a name in <c>global</c>.</p>
        <list type="bulleted">
          <item><c>fd</c> is an open descriptor to an Erlang
            connection.</item>
          <item><c>name</c> is the name to register in
            <c>global</c>.</item>
          <item><c>pid</c> is the pid that is to be associated with
            <c>name</c>. This value is returned by <c>global</c>
            when processes request the location of <c>name</c>.
          </item>
        </list>
        <p>Returns <c>0</c> on success, otherwise <c>-1</c>.</p>
      </desc>
    </func>

    <func>
      <name since=""><ret>int</ret><nametext>erl_global_unregister(fd,name)</nametext></name>
      <fsummary>Unregister a name from global.</fsummary>
      <type>
        <v>int fd;</v>
        <v>const char *name;</v>
      </type>
      <desc>
        <p>Unregisters a name from <c>global</c>.</p>
        <list type="bulleted">
          <item><c>fd</c> is an open descriptor to an Erlang
            connection.</item>
          <item><c>name</c> is the name to unregister from
            <c>global</c>.</item>
        </list>
        <p>Returns <c>0</c> on success, otherwise <c>-1</c>.</p>
      </desc>
    </func>

    <func>
      <name since=""><ret>ETERM *</ret><nametext>erl_global_whereis(fd,name,node)</nametext></name>
      <fsummary>Look up a name in global.</fsummary>
      <type>
        <v>int fd;</v>
        <v>const char *name;</v>
        <v>char *node;</v>
      </type>
      <desc>
        <p>Looks up a name in <c>global</c>.</p>
        <list type="bulleted">
          <item><c>fd</c> is an open descriptor to an Erlang
            connection.</item>
          <item><c>name</c> is the name that is to be looked up in
            <c>global</c>.</item>
        </list>
        <p>If <c>node</c> is not <c>NULL</c>, it is a pointer to a
          buffer where the function can fill in the name of the node where
          <c>name</c> is found. <c>node</c> can be
          passed directly to <c>erl_connect()</c> if necessary.</p>
        <p>On success, the function returns an Erlang pid containing the address
          of the specified name, and the node is initialized to
          the node name where <c>name</c> is found. On failure,
          <c>NULL</c> is returned and <c>node</c> is not
          modified.</p>
      </desc>
    </func>
  </funcs>
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