diff options
Diffstat (limited to 'lib/kernel/src/os.erl')
| -rw-r--r-- | lib/kernel/src/os.erl | 103 |
1 files changed, 81 insertions, 22 deletions
diff --git a/lib/kernel/src/os.erl b/lib/kernel/src/os.erl index f0ad26b1f2..92ac401b72 100644 --- a/lib/kernel/src/os.erl +++ b/lib/kernel/src/os.erl @@ -1,7 +1,7 @@ %% %% %CopyrightBegin% %% -%% Copyright Ericsson AB 1997-2016. All Rights Reserved. +%% Copyright Ericsson AB 1997-2017. All Rights Reserved. %% %% Licensed under the Apache License, Version 2.0 (the "License"); %% you may not use this file except in compliance with the License. @@ -21,7 +21,7 @@ %% Provides a common operating system interface. --export([type/0, version/0, cmd/1, find_executable/1, find_executable/2]). +-export([type/0, version/0, cmd/1, cmd/2, find_executable/1, find_executable/2]). -include("file.hrl"). @@ -32,6 +32,11 @@ putenv/2, system_time/0, system_time/1, timestamp/0, unsetenv/1]). +-type os_command() :: atom() | io_lib:chars(). +-type os_command_opts() :: #{ max_size => non_neg_integer() | infinity }. + +-export_type([os_command/0, os_command_opts/0]). + -spec getenv() -> [string()]. getenv() -> erlang:nif_error(undef). @@ -223,14 +228,22 @@ extensions() -> %% Executes the given command in the default shell for the operating system. -spec cmd(Command) -> string() when - Command :: atom() | io_lib:chars(). + Command :: os_command(). cmd(Cmd) -> + cmd(Cmd, #{ }). + +-spec cmd(Command, Options) -> string() when + Command :: os_command(), + Options :: os_command_opts(). +cmd(Cmd, Opts) -> validate(Cmd), - {SpawnCmd, SpawnOpts, SpawnInput} = mk_cmd(os:type(), Cmd), + {SpawnCmd, SpawnOpts, SpawnInput, Eot} = mk_cmd(os:type(), Cmd), Port = open_port({spawn, SpawnCmd}, [binary, stderr_to_stdout, - stream, in, eof, hide | SpawnOpts]), + stream, in, hide | SpawnOpts]), + MonRef = erlang:monitor(port, Port), true = port_command(Port, SpawnInput), - Bytes = get_data(Port, []), + Bytes = get_data(Port, MonRef, Eot, [], 0, maps:get(max_size, Opts, infinity)), + demonitor(MonRef, [flush]), String = unicode:characters_to_list(Bytes), if %% Convert to unicode list if possible otherwise return bytes is_list(String) -> String; @@ -243,7 +256,7 @@ mk_cmd({win32,Wtype}, Cmd) -> {false,_} -> lists:concat(["cmd /c", Cmd]); {Cspec,_} -> lists:concat([Cspec," /c",Cmd]) end, - {Command, [], []}; + {Command, [], [], <<>>}; mk_cmd(OsType,Cmd) when is_atom(Cmd) -> mk_cmd(OsType, atom_to_list(Cmd)); mk_cmd(_,Cmd) -> @@ -252,7 +265,20 @@ mk_cmd(_,Cmd) -> {"/bin/sh -s unix:cmd", [out], %% We insert a new line after the command, in case the command %% contains a comment character. - ["(", unicode:characters_to_binary(Cmd), "\n); exit\n"]}. + %% + %% The </dev/null closes stdin, which means that programs + %% that use a closed stdin as an termination indicator works. + %% An example of such a program is 'more'. + %% + %% The "echo ^D" is used to indicate that the program has executed + %% and we should return any output we have gotten. We cannot use + %% termination of the child or closing of stdin/stdout as then + %% starting background jobs from os:cmd will block os:cmd. + %% + %% I tried changing this to be "better", but got bombarded with + %% backwards incompatibility bug reports, so leave this as it is. + ["(", unicode:characters_to_binary(Cmd), "\n) </dev/null; echo \"\^D\"\n"], + <<$\^D>>}. validate(Atom) when is_atom(Atom) -> ok; @@ -267,21 +293,54 @@ validate1([List|Rest]) when is_list(List) -> validate1([]) -> ok. -get_data(Port, Sofar) -> +get_data(Port, MonRef, Eot, Sofar, Size, Max) -> receive {Port, {data, Bytes}} -> - get_data(Port, [Sofar,Bytes]); - {Port, eof} -> - Port ! {self(), close}, - receive - {Port, closed} -> - true - end, - receive - {'EXIT', Port, _} -> - ok - after 1 -> % force context switch - ok - end, + case eot(Bytes, Eot, Size, Max) of + more -> + get_data(Port, MonRef, Eot, [Sofar, Bytes], + Size + byte_size(Bytes), Max); + Last -> + catch port_close(Port), + flush_until_down(Port, MonRef), + iolist_to_binary([Sofar, Last]) + end; + {'DOWN', MonRef, _, _, _} -> + flush_exit(Port), iolist_to_binary(Sofar) end. + +eot(Bs, <<>>, Size, Max) when Size + byte_size(Bs) < Max -> + more; +eot(Bs, <<>>, Size, Max) -> + binary:part(Bs, {0, Max - Size}); +eot(Bs, Eot, Size, Max) -> + case binary:match(Bs, Eot) of + {Pos, _} when Size + Pos < Max -> + binary:part(Bs,{0, Pos}); + _ -> + eot(Bs, <<>>, Size, Max) + end. + +%% When port_close returns we know that all the +%% messages sent have been sent and that the +%% DOWN message is after them all. +flush_until_down(Port, MonRef) -> + receive + {Port, {data, _Bytes}} -> + flush_until_down(Port, MonRef); + {'DOWN', MonRef, _, _, _} -> + flush_exit(Port) + end. + +%% The exit signal is always delivered before +%% the down signal, so we can be sure that if there +%% was an exit message sent, it will be in the +%% mailbox now. +flush_exit(Port) -> + receive + {'EXIT', Port, _} -> + ok + after 0 -> + ok + end. |