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copied!<p>Printed process ids < A.B.C > are composed of <a href="http://github.com/mfoemmel/erlang-otp/blob/R13B/erts/emulator/beam/erl_term.h#L502" rel="noreferrer">6</a>:</p> <ul> <li>A, the node number (0 is the local node, an arbitrary number for a remote node) </li> <li>B, the first 15 bits of the process number (an index into the process table) <a href="http://github.com/mfoemmel/erlang-otp/blob/R13B/erts/emulator/beam/erl_term.h#L534" rel="noreferrer">7</a></li> <li>C, bits 16-18 of the process number (the same process number as B) <a href="http://github.com/mfoemmel/erlang-otp/blob/R13B/erts/emulator/beam/erl_term.h#L534" rel="noreferrer">7</a></li> </ul> <p>Internally, the process number is 28 bits wide on the 32 bit emulator. The odd definition of B and C comes from R9B and earlier versions of Erlang in which B was a 15bit process ID and C was a wrap counter incremented when the max process ID was reached and lower IDs were reused.</p> <p>In the erlang distribution PIDs are a little larger as they include the node atom as well as the other information. (<a href="http://erlang.org/doc/apps/erts/erl_ext_dist.html#8.8" rel="noreferrer">Distributed PID format</a>)</p> <p>When an internal PID is sent from one node to the other, it's automatically converted to the external/distributed PID form, so what might be <code><0.10.0></code> (<code>inet_db</code>) on one node might end up as <code><2265.10.0></code> when sent to another node. You can just send to these PIDs as normal.</p> <pre><code>% get the PID of the user server on OtherNode RemoteUser = rpc:call(OtherNode, erlang,whereis,[user]), true = is_pid(RemoteUser), % send message to remote PID RemoteUser ! ignore_this, % print "Hello from <nodename>\n" on the remote node's console. io:format(RemoteUser, "Hello from ~p~n", [node()]). </code></pre> <p>For more information see: <a href="http://github.com/mfoemmel/erlang-otp/tree/5b6dd0e84cf0f1dc19ddd05f86cf04b2695d8a9e/erts/emulator/beam/erl_term.h#L498" rel="noreferrer">Internal PID structure</a>, <a href="http://github.com/mfoemmel/erlang-otp/tree/5b6dd0e84cf0f1dc19ddd05f86cf04b2695d8a9e/erts/emulator/beam/erl_node_container_utils.h#L24" rel="noreferrer">Node creation information</a>, <a href="http://erlang.2086793.n4.nabble.com/PID-recycling-td2108252.html#a2108255" rel="noreferrer">Node creation counter interaction with EPMD</a></p>

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