mex: is_wsl()

Author: scivision

+stdlib/is_rosetta.m

@@ -1,4 +1,4 @@
-%% IS_ROSETTA on Apple Silicon via Rosetta (Matlab optional MEX)
+%% IS_ROSETTA on Apple Silicon via Rosetta (optional MEX)
 % true if Matlab on Apple Silicon CPU is built for Intel x86_64
 
 function r = is_rosetta()

+stdlib/is_symlink.m

@@ -1,4 +1,4 @@
-%% IS_SYMLINK is path a symbolic link (Matlab optional MEX)
+%% IS_SYMLINK is path a symbolic link (optional MEX)
 
 function ok = is_symlink(p)
 arguments

+stdlib/is_wsl.m

@@ -1,25 +1,27 @@
-%% IS_WSL detect if running under WSL
+%% IS_WSL detect if running under WSL (optional MEX)
 % Detects if Matlab or GNU Octave is installed and running from within
 % Windows Subsystem for Linux
 
 function w = is_wsl()
 
-persistent wsl;
+w = 0;
 
-if isempty(wsl)
-  wsl = false;
-  if isunix && ~ismac
-    fid = fopen('/proc/version');
-    if fid >= 1
-      v = fscanf(fid,'%s');
-      fclose(fid);
-      wsl = ~isempty(strfind(v, 'microsoft-standard')); %#ok<*STREMP>
+if isunix && ~ismac
+  fid = fopen('/proc/version');
+  if fid >= 1
+    v = fscanf(fid, '%s');
+    if fclose(fid) ~= 0
+      w = -1;
+    elseif endsWith(v, "microsoft-standard-WSL2")
+      w = 2;
+    elseif endsWith(v, "-Microsoft")
+      w = 1;
     end
   end
 end
 
-w = wsl; % has to be a separate line/variable for matlab
+w = int32(w);
 
 end
 
-%!assert(islogical(is_wsl()))
+%!assert(class(is_wsl()), "int32")

+stdlib/windows_shortname.m

@@ -1,4 +1,4 @@
-%% WINDOWS_SHORTNAME Retrieves the Windows short name (Matlab optional MEX)
+%% WINDOWS_SHORTNAME Retrieves the Windows short name (optional MEX)
 % (8.3 character) filename
 %
 %  Example of using a COM server (Scripting.FileSystemObject) in Windows

buildfile.m

@@ -88,13 +88,15 @@ function publishTask(context)
 end
 
 mac = "src/macos.cpp";
+linux = "src/linux_fs.cpp";
 
 sym = "src/symlink_fs.cpp";
 
 
 srcs = {
 ["src/is_admin.cpp", "src/admin_fs.cpp"] ...
 "src/is_char_device.cpp", ...
+["src/is_wsl.cpp", "src/linux_fs.cpp"], ...
 "src/set_permissions.cpp", ...
 ["src/is_rosetta.cpp", mac], ...
 ["src/windows_shortname.cpp", win], ...

octave_build.m

@@ -9,6 +9,7 @@
 
 %% specific source
 srcs = {
+fullfile(d, "is_wsl.cpp"), ...
 fullfile(d, "is_rosetta.cpp"), ...
 fullfile(d, "is_admin.cpp"), ...
 };

src/is_symlink.cpp

@@ -5,7 +5,6 @@
 #include "mexAdapter.hpp"
 
 #include <string>
-// note: <string_view> causes compile failures with MSVC at least
 
 #include <vector>
 #include <memory>

src/is_wsl.cpp

@@ -0,0 +1,27 @@
+#include "mex.hpp"
+#include "mexAdapter.hpp"
+
+#include <vector>
+#include <memory>
+
+#include "linux_fs.h"
+
+
+class MexFunction : public matlab::mex::Function {
+public:
+  void operator()(matlab::mex::ArgumentList outputs, matlab::mex::ArgumentList inputs) {
+// boilerplate engine & ArrayFactory setup
+    std::shared_ptr<matlab::engine::MATLABEngine> matlabEng = getEngine();
+    matlab::data::ArrayFactory factory;
+
+    if (inputs.size() != 0) {
+      matlabEng->feval(u"error", 0,
+        std::vector<matlab::data::Array>({ factory.createScalar("Mex: No input required") }));
+    }
+
+// actual function algorithm / computation
+    int wsl = fs_is_wsl();
+
+    outputs[0] = factory.createScalar<int>(wsl);
+  }
+};

src/linux_fs.cpp

@@ -0,0 +1,32 @@
+#include <string_view>
+
+#if __has_include(<sys/utsname.h>)
+#define HAVE_UTSNAME
+#include <sys/utsname.h>
+#endif
+
+#include "linux_fs.h"
+
+
+int fs_is_wsl()
+{
+
+#ifdef HAVE_UTSNAME
+  struct utsname buf;
+  if (uname(&buf) != 0)
+    return -1;
+
+  std::string_view s(buf.sysname);
+  std::string_view r(buf.release);
+
+  if(s != "Linux")
+    return 0;
+#ifdef __cpp_lib_starts_ends_with // C++20
+  if (r.ends_with("microsoft-standard-WSL2"))
+    return 2;
+  if (r.ends_with("-Microsoft"))
+    return 1;
+#endif
+#endif
+  return 0;
+}

src/linux_fs.h

@@ -0,0 +1 @@
+int fs_is_wsl();