Add the ERL_SYS_SHELL env variable to point to system shell for os:cmd()

lib/kernel/doc/kernel_app.md

@@ -512,6 +512,10 @@ For more information about configuration parameters, see file
   [Escripts and non-interactive I/O in Unicode Usage in Erlang](`e:stdlib:unicode_usage.md#escripts-and-non-interactive-i-o`)
   for more details.
 
+- **`os_cmd_shell = string()`{: #os_cmd_shell }** - Specifies which shell to
+  use when invoking system commands via `os:cmd/2`. By default the shell is detected
+  automatically.
+
 ## Deprecated Configuration Parameters
 
 In Erlang/OTP 21.0, a new API for logging was added. The old `error_logger`

lib/kernel/src/kernel.erl

@@ -33,6 +33,7 @@
 start(_, []) ->
     %% Setup the logger and configure the kernel logger environment
     ok = logger:internal_init_logger(),
+    ok = os:internal_init_cmd_shell(),
     case supervisor:start_link({local, kernel_sup}, kernel, []) of
 	{ok, Pid} ->
             ok = erl_signal_handler:start(),

lib/kernel/src/os.erl

@@ -37,6 +37,8 @@ a program to run on most platforms.
 
 -export([type/0, version/0, cmd/1, cmd/2, find_executable/1, find_executable/2]).
 
+-export([internal_init_cmd_shell/0]).
+
 -include("file.hrl").
 
 -export_type([env_var_name/0, env_var_value/0, env_var_name_value/0]).
@@ -518,6 +520,10 @@ cmd(Cmd) ->
 Executes `Command` in a command shell of the target OS, captures the standard
 output and standard error of the command, and returns this result as a string.
 
+The command shell can be set using the
+[kernel configuration parameter](kernel_app.md#os_cmd_shell), by default the
+shell is detected upon system startup.
+
 _Examples:_
 
 ```erlang
@@ -581,35 +587,14 @@ get_option(Opt, Options, Default) ->
         _ -> throw(badopt)
     end.
 
-mk_cmd({win32,Wtype}, Cmd) ->
-    Command = case {os:getenv("COMSPEC"),Wtype} of
-                  {false,windows} -> lists:concat(["command.com /c", Cmd]);
-                  {false,_} -> lists:concat(["cmd /c", Cmd]);
-                  {Cspec,_} -> lists:concat([Cspec," /c",Cmd])
-              end,
+mk_cmd({win32,_}, Cmd) ->
+    {ok, Shell} = application:get_env(kernel, os_cmd_shell),
+    Command = lists:concat([Shell, " /c", Cmd]),
     {Command, [], [], <<>>};
 mk_cmd(_,Cmd) ->
     %% Have to send command in like this in order to make sh commands like
     %% cd and ulimit available.
-    %%
-    %% We use an absolute path here because we do not want the path to be
-    %% searched in case a stale NFS handle is somewhere in the path before
-    %% the sh command.
-    %%
-    %% Check if the default shell is located in /bin/sh as expected usually
-    %% or in /system/bin/sh as implemented on Android. The raw option is
-    %% used to bypass the file server and speed up the file access.
-    Shell = case file:read_file_info("/bin/sh",[raw]) of
-                {ok,#file_info{type=regular}} ->
-                    "/bin/sh";
-                _ ->
-                    case file:read_file_info("/system/bin/sh",[raw]) of
-                        {ok,#file_info{type=regular}} ->
-                            "/system/bin/sh";
-                        _ ->
-                            "/bin/sh"
-                    end
-            end,
+    {ok, Shell} = application:get_env(kernel, os_cmd_shell),
     {Shell ++ " -s unix:cmd", [out],
      %% We insert a new line after the command, in case the command
      %% contains a comment character.
@@ -628,6 +613,41 @@ mk_cmd(_,Cmd) ->
      ["(", unicode:characters_to_binary(Cmd), "\n) </dev/null; echo \"\^D\"\n"],
      <<$\^D>>}.
 
+-doc false.
+internal_init_cmd_shell() ->
+    case application:get_env(kernel, os_cmd_shell) of
+        undefined ->
+            application:set_env(kernel, os_cmd_shell,
+            internal_init_cmd_shell(os:type()));
+        _ ->
+            ok
+    end.
+internal_init_cmd_shell({win32,Wtype}) ->
+    case {os:getenv("COMSPEC"),Wtype} of
+        {false,windows} -> "command.com";
+        {false,_} -> "cmd";
+        {Cspec,_} -> Cspec
+    end;
+internal_init_cmd_shell(_) ->
+    %% We use an absolute path here because we do not want the path to be
+    %% searched in case a stale NFS handle is somewhere in the path before
+    %% the sh command.
+    %%
+    %% Check if the default shell is located in /bin/sh as expected usually
+    %% or in /system/bin/sh as implemented on Android. The raw option is
+    %% used to bypass the file server.
+    case file:read_file_info("/bin/sh",[raw]) of
+        {ok,#file_info{type=regular}} ->
+            "/bin/sh";
+        _ ->
+            case file:read_file_info("/system/bin/sh",[raw]) of
+                {ok,#file_info{type=regular}} ->
+                    "/system/bin/sh";
+                _ ->
+                    "/bin/sh"
+            end
+    end.
+
 validate(Term) ->
     try validate1(Term)
     catch error:_ -> throw(badarg)

lib/kernel/test/application_SUITE.erl

@@ -2060,6 +2060,7 @@ do_configfd_test_bash() ->
                 Command =
                     lists:flatten(io_lib:format("bash -c \"~s\"",
                                                 [quote_sub_strings(String)])),
+                os:internal_init_cmd_shell(),
                 Res = os:cmd(Command),
                 io:format("Command:~n"),
                 io:format("~s~n", [Command]),
@@ -2255,6 +2256,7 @@ total_memory() ->
 configfd_bash(Conf) when is_list(Conf) ->
     case os:type() of
     	{unix,_} ->
+            os:internal_init_cmd_shell(),
             case os:cmd("bash -c \"echo -n yes_bash_shell_exists\"") of
                 "yes_bash_shell_exists" ->
                     do_configfd_test_bash();

lib/kernel/test/erl_distribution_SUITE.erl

@@ -126,6 +126,7 @@ groups() ->
        xdg_cookie]}].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     start_gen_tcp_dist_test_type_server(),
     Config.
 

lib/kernel/test/file_SUITE.erl

@@ -189,6 +189,7 @@ end_per_group(_GroupName, Config) ->
 
 
 init_per_suite(Config) when is_list(Config) ->
+    os:internal_init_cmd_shell(),
     SaslConfig = case application:start(sasl) of
 		     {error, {already_started, sasl}} ->
 			 [];

lib/kernel/test/file_name_SUITE.erl

@@ -96,6 +96,7 @@ groups() ->
     [].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     Config.
 
 end_per_suite(_Config) ->

lib/kernel/test/gen_tcp_misc_SUITE.erl

@@ -358,6 +358,7 @@ socket_monitor_cases() ->
     ].
 
 init_per_suite(Config0) ->
+    os:internal_init_cmd_shell(),
 
     ?P("init_per_suite -> entry with"
        "~n      Config: ~p"

lib/kernel/test/global_SUITE.erl

@@ -159,6 +159,7 @@ end_per_group(_GroupName, Config) ->
     Config.
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     Config.
 
 end_per_suite(_Config) ->

lib/kernel/test/inet_SUITE.erl

@@ -122,6 +122,7 @@ required(hosts) ->
 
 
 init_per_suite(Config0) ->
+    os:internal_init_cmd_shell(),
 
     ?P("init_per_suite -> entry with"
        "~n      Config: ~p"

lib/kernel/test/init_SUITE.erl

@@ -60,6 +60,7 @@ groups() ->
     [{boot, [], [boot1, boot2]}].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     Config.
 
 end_per_suite(_Config) ->

lib/kernel/test/interactive_shell_SUITE.erl

@@ -144,6 +144,7 @@ groups() ->
     ].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     Term = os:getenv("TERM", "dumb"),
     os:putenv("TERM", "vt100"),
     [{term,Term}|Config].

lib/kernel/test/kernel_config_SUITE.erl

@@ -44,6 +44,7 @@ end_per_group(_GroupName, Config) ->
 
 
 init_per_suite(Config) when is_list(Config) ->
+    os:internal_init_cmd_shell(),
     Config.
 
 end_per_suite(Config) when is_list(Config) ->

lib/kernel/test/kernel_test_lib.erl

@@ -72,11 +72,14 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 init_per_suite([{allow_skip, Allow}|Config]) ->
+    os:internal_init_cmd_shell(),
     init_per_suite(Allow, Config);
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     init_per_suite(true, Config).
 
 init_per_suite(AllowSkip, Config) when is_boolean(AllowSkip) ->
+    os:internal_init_cmd_shell(),
 
     print("kernel environment: "
           "~n   (kernel) app:  ~p"

lib/kernel/test/logger_simple_h_SUITE.erl

@@ -48,6 +48,7 @@ suite() ->
     [{timetrap,{seconds,30}}].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     Hs0 = logger:get_handler_config(),
     Hs = lists:keydelete(cth_log_redirect,1,Hs0),
     [ok = logger:remove_handler(Id) || {Id,_,_} <- Hs],

lib/kernel/test/os_SUITE.erl

@@ -28,7 +28,7 @@
 	 find_executable/1, unix_comment_in_command/1, deep_list_command/1,
          large_output_command/1, background_command/0, background_command/1,
          message_leak/1, close_stdin/0, close_stdin/1, max_size_command/1,
-         perf_counter_api/1, error_info/1]).
+         perf_counter_api/1, error_info/1, os_cmd_shell/1]).
 
 -include_lib("common_test/include/ct.hrl").
 
@@ -43,12 +43,13 @@ all() ->
      find_executable, unix_comment_in_command, deep_list_command,
      large_output_command, background_command, message_leak,
      close_stdin, max_size_command, perf_counter_api,
-     error_info].
+     error_info, os_cmd_shell].
 
 groups() ->
     [].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     Config.
 
 end_per_suite(_Config) ->
@@ -469,6 +470,21 @@ error_info(Config) ->
         ],
     error_info_lib:test_error_info(os, L).
 
+os_cmd_shell(Config) ->
+    DataDir = proplists:get_value(data_dir, Config),
+    SysShell = filename:join(DataDir, "sys_shell"),
+
+    {ok, OldShell} = application:get_env(kernel, os_cmd_shell),
+    try
+        application:set_env(kernel, os_cmd_shell, SysShell),
+
+        %% os:cmd should not try to detect the shell location rather than use
+        %% the value from kernel:os_cmd_shell parameter
+        comp("sys_shell", os:cmd("ls"))
+    after
+        application:set_env(kernel, os_cmd_shell, OldShell),
+    end.
+
 no_limit_for_opened_files() ->
     case os:type() of
         {unix, freebsd} ->

lib/kernel/test/os_SUITE_data/Makefile.src

@@ -3,7 +3,7 @@ LD = @LD@
 CFLAGS = @CFLAGS@ -I@erl_include@ @DEFS@
 CROSSLDFLAGS = @CROSSLDFLAGS@
 
-PROGS = my_echo@exe@ my_fds@exe@
+PROGS = my_echo@exe@ my_fds@exe@ sys_shell@exe@
 
 all: $(PROGS)
 
@@ -18,3 +18,9 @@ my_fds@exe@: my_fds@obj@
 
 my_fds@obj@: my_fds.c
 	$(CC) -c -o my_fds@obj@ $(CFLAGS) my_fds.c
+
+sys_shell@exe@: sys_shell@obj@
+	$(LD) $(CROSSLDFLAGS) -o sys_shell sys_shell@obj@ @LIBS@
+
+sys_shell@obj@: sys_shell.c
+	$(CC) -c -o sys_shell@obj@ $(CFLAGS) sys_shell.c

lib/kernel/test/os_SUITE_data/sys_shell.c

@@ -0,0 +1,6 @@
+#include <stdio.h>
+int main(void)
+{
+    printf("sys_shell");
+    return 0;
+}

lib/kernel/test/prim_file_SUITE.erl

@@ -100,6 +100,7 @@ end_per_group(_GroupName, Config) ->
 
 
 init_per_suite(Config) when is_list(Config) ->
+    os:internal_init_cmd_shell(),
     case os:type() of
 	{win32, _} ->
 	    Priv = proplists:get_value(priv_dir, Config),

lib/kernel/test/sendfile_SUITE.erl

@@ -60,6 +60,7 @@ all() ->
      t_sendfile_arguments].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     case {os:type(),os:version()} of
 	{{unix,sunos}, {5,8,_}} ->
 	    {skip, "Solaris 8 not supported for now"};

lib/kernel/test/seq_trace_SUITE.erl

@@ -61,6 +61,7 @@ groups() ->
     [].
 
 init_per_suite(Config) ->
+    os:internal_init_cmd_shell(),
     Config.
 
 end_per_suite(_Config) ->

lib/kernel/test/socket_SUITE.erl

@@ -398,6 +398,7 @@ otp18240_cases() ->
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 init_per_suite(Config0) ->
+    os:internal_init_cmd_shell(),
     ?P("init_per_suite -> entry with"
        "~n      Config: ~p"
        "~n      Nodes:  ~p", [Config0, erlang:nodes()]),

lib/kernel/test/socket_api_SUITE.erl

@@ -667,6 +667,7 @@ api_op_with_timeout_cases() ->
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 init_per_suite(Config0) ->
+    os:internal_init_cmd_shell(),
     ?P("init_per_suite -> entry with"
        "~n      Config: ~p"
        "~n      Nodes:  ~p", [Config0, erlang:nodes()]),

lib/kernel/test/socket_traffic_SUITE.erl

@@ -307,6 +307,7 @@ traffic_pp_sendmsg_recvmsg_cases() ->
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 init_per_suite(Config0) ->
+    os:internal_init_cmd_shell(),
     ?P("init_per_suite -> entry with"
        "~n      Config: ~p"
        "~n      Nodes:  ~p", [Config0, erlang:nodes()]),