--- a/UnixOperatingSystem.st	Tue Sep 27 14:56:57 2016 +0200
+++ b/UnixOperatingSystem.st	Tue Sep 27 15:03:13 2016 +0200
@@ -3785,13 +3785,14 @@
     |info path|
 
     "shortcut - use the /proc filesystem (if present).
-     Here we get an absolute path to the running executable."
+     Here we get an absolute path to the running executable.
+     Notice: we cannot depend on /proc to be present (actually only is on linux)"
     info := '/proc/self/exe' asFilename linkInfo.
     info notNil ifTrue:[
-	path := info path.
-	path notEmptyOrNil ifTrue:[
-	    ^ path
-	].
+        path := info path.
+        path notEmptyOrNil ifTrue:[
+            ^ path
+        ].
      ].
 
     "Fall back - do it the hard way"
@@ -3804,27 +3805,24 @@
 !
 
 pathOfCommand:aCommand
-    "find where aCommand's executable file is;
-     return its full pathName if there is such a command, 
-     otherwise return nil.
-     This does not check if there really is an existing/executable command/program 
-     at the path's file - only which path would be chosen.
-     To answer that question, use #canExecuteCommand:."
+    "find where aCommand's executable file would be searched for if executed by a shell.
+     Return nil if aCommand is either absolute, or relative and not executable,
+     or not executable is found along the PATH."
 
     |path f fExt commandFilename|
 
     commandFilename := aCommand asFilename.
     commandFilename isAbsolute ifTrue:[
         "/ something like "/foo/...", tried path is it
-        ^ commandFilename pathName
+        ^ commandFilename pathName isExecutable
     ].
     commandFilename isExplicitRelative ifTrue:[
         "/ something like "../foo/...", tried path resolved relative to the current directory
-         ^ commandFilename pathName
+         ^ commandFilename pathName isExecutable
     ].
     (aCommand includes:$/) ifTrue:[
         "/ something like "smalltalk/stx", tried path is relative to the current directory
-        ^ ('./',aCommand) asFilename pathName
+        ^ ('./',aCommand) asFilename pathName isExecutable
     ].
 
     "/ command is a single word, not relative and not absolute.