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Diffstat (limited to 'system/doc/reference_manual/ports.xml')
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1 files changed, 75 insertions, 39 deletions
diff --git a/system/doc/reference_manual/ports.xml b/system/doc/reference_manual/ports.xml index 621af10624..e5dc99641b 100644 --- a/system/doc/reference_manual/ports.xml +++ b/system/doc/reference_manual/ports.xml @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>2004</year><year>2013</year> + <year>2004</year><year>2015</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -28,9 +28,12 @@ <rev></rev> <file>ports.xml</file> </header> - <p>Examples of how to use ports and port drivers can be found in - <em>Interoperability Tutorial</em>. The BIFs mentioned are as usual - documented in <c>erlang(3)</c>.</p> + <p>Examples of how to use ports and port drivers are provided in + <seealso marker="doc/tutorial:introduction#interoperability tutorial"> + Interoperability Tutorial</seealso>. + For information about the BIFs mentioned, see the + <seealso marker="erts:erlang">erlang(3)</seealso> manual + page in ERTS.</p> <section> <title>Ports</title> @@ -39,29 +42,34 @@ provide a byte-oriented interface to an external program. When a port has been created, Erlang can communicate with it by sending and receiving lists of bytes, including binaries.</p> - <p>The Erlang process which creates a port is said to be + <p>The Erlang process creating a port is said to be the <em>port owner</em>, or the <em>connected process</em> of - the port. All communication to and from the port should go via - the port owner. If the port owner terminates, so will the port + the port. All communication to and from the port must go through + the port owner. If the port owner terminates, so does the port (and the external program, if it is written correctly).</p> <p>The external program resides in another OS process. By default, - it should read from standard input (file descriptor 0) and write + it reads from standard input (file descriptor 0) and writes to standard output (file descriptor 1). The external program - should terminate when the port is closed.</p> + is to terminate when the port is closed.</p> </section> <section> <title>Port Drivers</title> - <p>It is also possible to write a driver in C according to certain + <p>It is possible to write a driver in C according to certain principles and dynamically link it to the Erlang runtime system. The linked-in driver looks like a port from the Erlang programmer's point of view and is called a <em>port driver</em>.</p> <warning> - <p>An erroneous port driver will cause the entire Erlang runtime + <p>An erroneous port driver causes the entire Erlang runtime system to leak memory, hang or crash.</p> </warning> - <p>Port drivers are documented in <c>erl_driver(4)</c>, - <c>driver_entry(1)</c> and <c>erl_ddll(3)</c>.</p> + <p>For information about port drivers, see the + <seealso marker="erts:erl_driver">erl_driver(4)</seealso> + manual page in ERTS, + <seealso marker="erts:driver_entry">driver_entry(1)</seealso> + manual page in ERTS, and + <seealso marker="kernel:erl_ddll">erl_ddll(3)</seealso> + manual page in Kernel.</p> </section> <section> @@ -70,53 +78,74 @@ <table> <row> <cell align="left" valign="middle"><c>open_port(PortName, PortSettings</c></cell> - <cell align="left" valign="middle">Returns a port identifier <c>Port</c>as the result of opening a new Erlang port. Messages can be sent to and received from a port identifier, just like a pid. Port identifiers can also be linked to or registered under a name using <c>link/1</c>and <c>register/2</c>.</cell> + <cell align="left" valign="middle">Returns a port identifier + <c>Port</c> as the result of opening a new Erlang port. + Messages can be sent to, and received from, a port identifier, + just like a pid. Port identifiers can also be linked to + using <c>link/1</c>, or registered under a name using + <c>register/2</c>.</cell> </row> - <tcaption>Port Creation BIF.</tcaption> + <tcaption>Port Creation BIF</tcaption> </table> <p><c>PortName</c> is usually a tuple <c>{spawn,Command}</c>, where the string <c>Command</c> is the name of the external program. - The external program runs outside the Erlang workspace unless a - port driver with the name <c>Command</c> is found. If found, that - driver is started.</p> + The external program runs outside the Erlang workspace, unless a + port driver with the name <c>Command</c> is found. If <c>Command</c> + is found, that driver is started.</p> <p><c>PortSettings</c> is a list of settings (options) for the port. - The list typically contains at least a tuple <c>{packet,N}</c> + The list typically contains at least a tuple <c>{packet,N}</c>, which specifies that data sent between the port and the external program are preceded by an N-byte length indicator. Valid values - for N are 1, 2 or 4. If binaries should be used instead of lists + for N are 1, 2, or 4. If binaries are to be used instead of lists of bytes, the option <c>binary</c> must be included.</p> <p>The port owner <c>Pid</c> can communicate with the port <c>Port</c> by sending and receiving messages. (In fact, any process can send the messages to the port, but the port owner must be identified in the message).</p> - <p>As of OTP-R16 messages sent to ports are delivered truly + <p>As of Erlang/OTP R16, messages sent to ports are delivered truly asynchronously. The underlying implementation previously delivered messages to ports synchronously. Message passing has - however always been documented as an asynchronous operation, so - this should not be an issue for an Erlang program communicating - with ports, unless false assumptions about ports has been made.</p> - <p>Below, <c>Data</c> must be an I/O list. An I/O list is a binary - or a (possibly deep) list of binaries or integers in the range - 0..255.</p> + however always been documented as an asynchronous operation. Hence, + this is not to be an issue for an Erlang program communicating + with ports, unless false assumptions about ports have been made.</p> + <p>In the following tables of examples, <c>Data</c> must be an I/O list. + An I/O list is a binary or a (possibly deep) list of binaries + or integers in the range 0..255:</p> <table> <row> + <cell align="left" valign="middle"><em>Message</em></cell> + <cell align="left" valign="middle"><em>Description</em></cell> + </row> + <row> <cell align="left" valign="middle"><c>{Pid,{command,Data}}</c></cell> - <cell align="left" valign="middle">Sends <c>Data</c>to the port.</cell> + <cell align="left" valign="middle">Sends <c>Data</c> to the port.</cell> </row> <row> <cell align="left" valign="middle"><c>{Pid,close}</c></cell> - <cell align="left" valign="middle">Closes the port. Unless the port is already closed, the port replies with <c>{Port,closed}</c>when all buffers have been flushed and the port really closes.</cell> + <cell align="left" valign="middle">Closes the port. Unless the + port is already closed, the port replies with + <c>{Port,closed}</c> when all buffers have been flushed + and the port really closes.</cell> </row> <row> <cell align="left" valign="middle"><c>{Pid,{connect,NewPid}}</c></cell> - <cell align="left" valign="middle">Sets the port owner of <c>Port</c>to <c>NewPid</c>. Unless the port is already closed, the port replies with<c>{Port,connected}</c>to the old port owner. Note that the old port owner is still linked to the port, but the new port owner is not.</cell> + <cell align="left" valign="middle">Sets the port owner of + <c>Port</c>to <c>NewPid</c>. Unless the port is already closed, + the port replies with<c>{Port,connected}</c> to the old + port owner. Note that the old port owner is still linked + to the port, but the new port owner is not.</cell> </row> - <tcaption>Messages Sent To a Port.</tcaption> + <tcaption>Messages Sent To a Port</tcaption> </table> + <p></p> <table> <row> + <cell align="left" valign="middle"><em>Message</em></cell> + <cell align="left" valign="middle"><em>Description</em></cell> + </row> + <row> <cell align="left" valign="middle"><c>{Port,{data,Data}}</c></cell> - <cell align="left" valign="middle"><c>Data</c>is received from the external program.</cell> + <cell align="left" valign="middle"><c>Data</c> is received from the external program.</cell> </row> <row> <cell align="left" valign="middle"><c>{Port,closed}</c></cell> @@ -124,20 +153,24 @@ </row> <row> <cell align="left" valign="middle"><c>{Port,connected}</c></cell> - <cell align="left" valign="middle">Reply to <c>Port ! {Pid,{connect,NewPid}}</c></cell> + <cell align="left" valign="middle">Reply to <c>Port ! {Pid,{connect,NewPid}}</c>.</cell> </row> <row> <cell align="left" valign="middle"><c>{'EXIT',Port,Reason}</c></cell> <cell align="left" valign="middle">If the port has terminated for some reason.</cell> </row> - <tcaption>Messages Received From a Port.</tcaption> + <tcaption>Messages Received From a Port</tcaption> </table> <p>Instead of sending and receiving messages, there are also a - number of BIFs that can be used.</p> + number of BIFs that can be used:</p> <table> <row> + <cell align="left" valign="middle"><em>Port BIF</em></cell> + <cell align="left" valign="middle"><em>Description</em></cell> + </row> + <row> <cell align="left" valign="middle"><c>port_command(Port,Data)</c></cell> - <cell align="left" valign="middle">Sends <c>Data</c>to the port.</cell> + <cell align="left" valign="middle">Sends <c>Data</c> to the port.</cell> </row> <row> <cell align="left" valign="middle"><c>port_close(Port)</c></cell> @@ -145,7 +178,10 @@ </row> <row> <cell align="left" valign="middle"><c>port_connect(Port,NewPid)</c></cell> - <cell align="left" valign="middle">Sets the port owner of <c>Port</c>to <c>NewPid</c>. The old port owner <c>Pid</c>stays linked to the port and have to call <c>unlink(Port)</c>if this is not desired.</cell> + <cell align="left" valign="middle">Sets the port owner of + <c>Port</c>to <c>NewPid</c>. The old port owner <c>Pid</c> + stays linked to the port and must call <c>unlink(Port)</c> + if this is not desired.</cell> </row> <row> <cell align="left" valign="middle"><c>erlang:port_info(Port,Item)</c></cell> @@ -155,9 +191,9 @@ <cell align="left" valign="middle"><c>erlang:ports()</c></cell> <cell align="left" valign="middle">Returns a list of all ports on the current node.</cell> </row> - <tcaption>Port BIFs.</tcaption> + <tcaption>Port BIFs</tcaption> </table> - <p>There are some additional BIFs that only apply to port drivers: + <p>Some additional BIFs that apply to port drivers: <c>port_control/3</c> and <c>erlang:port_call/3</c>.</p> </section> </chapter> |