Extend erlang:port_info/1,2 to show the OS pid of a spawned process

When spawning OS (unix) processes with erlang:open_port, store the
resulting unix pid so that it can be queried later on using
erlang:port_info/1,2.

7 files changed, 51 insertions, 2 deletions

diff --git a/erts/doc/src/erlang.xml b/erts/doc/src/erlang.xml
index 30e3b02a0a..3664bdf76d 100644
--- a/erts/doc/src/erlang.xml
+++ b/erts/doc/src/erlang.xml
@@ -3084,6 +3084,10 @@ os_prompt%</pre>
             <p><c><anno>Bytes</anno></c> is the total number of bytes written to
               the port.</p>
           </item>
+          <tag><c>{os_pid, Integer}</c></tag>
+          <item>
+            <p><c>Integer</c> is the OS pid of the spawned process (Unix systems only).</p>
+          </item>
         </taglist>
         <p>Failure: <c>badarg</c> if <c><anno>Port</anno></c> is not a local port.</p>
       </desc>
diff --git a/erts/emulator/beam/atom.names b/erts/emulator/beam/atom.names
index 7be40976f6..2c6e80a3c3 100644
--- a/erts/emulator/beam/atom.names
+++ b/erts/emulator/beam/atom.names
@@ -390,6 +390,7 @@ atom opt
 atom or
 atom ordered_set
 atom orelse
+atom os_pid
 atom os_type
 atom os_version
 atom ose_bg_proc
diff --git a/erts/emulator/beam/erl_bif_info.c b/erts/emulator/beam/erl_bif_info.c
index ebd475f73a..e198be67c7 100644
--- a/erts/emulator/beam/erl_bif_info.c
+++ b/erts/emulator/beam/erl_bif_info.c
@@ -2741,7 +2741,8 @@ port_info_1(BIF_ALIST_1)
 	am_id,
 	am_connected,
 	am_input,
-	am_output
+	am_output,
+	am_os_pid
     };
     Eterm items[ASIZE(keys)];
     Eterm result = NIL;
@@ -2798,6 +2799,7 @@ port_info_1(BIF_ALIST_1)
 **    name        String
 **    input       Number of bytes input from port program
 **    output      Number of bytes output to the port program
+**    os_pid      The child's process ID
 */
 
 BIF_RETTYPE port_info_2(BIF_ALIST_2)
@@ -2898,6 +2900,18 @@ static BIF_RETTYPE port_info(Process* p, Eterm portid, Eterm item)
 	hp = HAlloc(p, hsz);
 	res = erts_bld_uint(&hp, NULL, n);
     }
+    else if (item == am_os_pid) {
+        if (prt->os_pid >= 0) {
+            Uint hsz = 3;
+            Uint n = prt->os_pid;
+            (void) erts_bld_uint(NULL, &hsz, n);
+            hp = HAlloc(p, hsz);
+            res = erts_bld_uint(&hp, NULL, n);
+        } else {
+	    hp = HAlloc(p, 3);
+	    res = am_undefined;
+        }
+    }
     else if (item == am_registered_name) {
 	RegProc *reg;
 	reg = prt->reg;
diff --git a/erts/emulator/beam/global.h b/erts/emulator/beam/global.h
index 6eac0db363..1431e08610 100644
--- a/erts/emulator/beam/global.h
+++ b/erts/emulator/beam/global.h
@@ -174,6 +174,7 @@ struct port {
     char *name;		         /* String used in the open */
     erts_driver_t* drv_ptr;
     UWord drv_data;
+    pid_t os_pid;                /* Child process ID */
     ErtsProcList *suspended;	 /* List of suspended processes. */
     LineBuf *linebuf;            /* Buffer to hold data not ready for
 				    process to get (line oriented I/O)*/
diff --git a/erts/emulator/beam/io.c b/erts/emulator/beam/io.c
index b23b1f628d..3deb386621 100644
--- a/erts/emulator/beam/io.c
+++ b/erts/emulator/beam/io.c
@@ -425,6 +425,7 @@ setup_port(Port* prt, Eterm pid, erts_driver_t *driver,
     sys_strcpy(new_name, name);
     erts_smp_runq_lock(runq);
     erts_smp_port_state_lock(prt);    
+    prt->os_pid = -1;
     prt->status = ERTS_PORT_SFLG_CONNECTED | xstatus;
     prt->snapshot = erts_smp_atomic32_read_nob(&erts_ports_snapshot);    
     old_name = prt->name;
diff --git a/erts/emulator/sys/unix/sys.c b/erts/emulator/sys/unix/sys.c
index f94e0f2296..bf69f3bf90 100644
--- a/erts/emulator/sys/unix/sys.c
+++ b/erts/emulator/sys/unix/sys.c
@@ -1163,6 +1163,8 @@ static int set_driver_data(int port_num,
 	report_exit_list = report_exit;
     }
 
+    erts_port[port_num].os_pid = pid;
+
     if (read_write & DO_READ) {
 	driver_data[ifd].packet_bytes = packet_bytes;
 	driver_data[ifd].port_num = port_num;
diff --git a/erts/emulator/test/port_bif_SUITE.erl b/erts/emulator/test/port_bif_SUITE.erl
index d9c82aba0e..f4ba502be5 100644
--- a/erts/emulator/test/port_bif_SUITE.erl
+++ b/erts/emulator/test/port_bif_SUITE.erl
@@ -24,6 +24,7 @@
 	 init_per_group/2,end_per_group/2, command/1,
 	 command_e_1/1, command_e_2/1, command_e_3/1, command_e_4/1,
 	 port_info1/1, port_info2/1,
+	 port_info_os_pid/1,
 	 connect/1, control/1, echo_to_busy/1]).
 
 -export([do_command_e_1/1, do_command_e_2/1, do_command_e_4/1]).
@@ -41,7 +42,7 @@ all() ->
 groups() -> 
     [{command_e, [],
       [command_e_1, command_e_2, command_e_3, command_e_4]},
-     {port_info, [], [port_info1, port_info2]}].
+     {port_info, [], [port_info1, port_info2, port_info_os_pid]}].
 
 init_per_suite(Config) ->
     Config.
@@ -196,6 +197,7 @@ port_info1(Config) when is_list(Config) ->
     ?line {value,{connected,_}}=lists:keysearch(connected, 1, A),
     ?line {value,{input,0}}=lists:keysearch(input, 1, A),
     ?line {value,{output,0}}=lists:keysearch(output, 1, A),
+    ?line {value,{os_pid,undefined}}=lists:keysearch(os_pid, 1, A),  % linked-in driver doesn't have a OS pid
     ?line true=erlang:port_close(P),
     ok.
 
@@ -215,6 +217,7 @@ port_info2(Config) when is_list(Config) ->
     ?line {connected, Me} = erlang:port_info(P, connected),
     ?line {input, 0}=erlang:port_info(P, input),
     ?line {output,0}=erlang:port_info(P, output),
+    ?line {os_pid, undefined}=erlang:port_info(P, os_pid),  % linked-in driver doesn't have a OS pid
 
     ?line erlang:port_control(P, $i, "abc"),
     ?line receive
@@ -229,6 +232,29 @@ port_info2(Config) when is_list(Config) ->
     ?line true = erlang:port_close(P),
     ok.
 
+%% Tests the port_info/1,2 os_pid option BIF
+port_info_os_pid(Config) when is_list(Config) ->
+    case os:type() of
+	{unix,_} ->
+	    do_port_info_os_pid();
+	_ ->
+	    {skip,"Only on Unix."}
+    end.
+
+do_port_info_os_pid() ->
+    ?line P = open_port({spawn, "echo $$"}, [eof]),
+    ?line A = erlang:port_info(P),
+    ?line {os_pid, InfoOSPid} = erlang:port_info(P, os_pid),
+    ?line EchoPidStr = receive
+	    {P, {data, EchoPidStr0}} -> EchoPidStr0
+	    after 10000 -> ?line test_server:fail(timeout)
+    end,
+    ?line {ok, [EchoPid], []} = io_lib:fread("~u\n", EchoPidStr),
+    ?line {value,{os_pid, InfoOSPid}}=lists:keysearch(os_pid, 1, A),
+    ?line EchoPid = InfoOSPid,
+    ?line true = erlang:port_close(P),
+    ok.
+
 output_test(_, _, Input, Output) when Output > 16#1fffffff ->
     io:format("~p bytes received\n", [Input]);
 output_test(P, Bin, Input0, Output0) ->