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 const Ci = Components.interfaces;

 const Cc = Components.classes;

 const NS_OS_TEMP_DIR = "TmpD";

 const CWD = do_get_cwd();

 function checkOS(os) {

   const nsILocalFile_ = "nsILocalFile" + os;

   return nsILocalFile_ in Components.interfaces &&

          CWD instanceof Components.interfaces[nsILocalFile_];

 }

 const isWin = checkOS("Win");

 const isMac = checkOS("Mac");

 const isUnix = !(isWin || isMac);

 var hiddenUnixFile;

 function createUNIXHiddenFile() {

   var dirSvc = Cc["@mozilla.org/file/directory_service;1"].getService(Ci.nsIProperties);

   var tmpDir = dirSvc.get(NS_OS_TEMP_DIR, Ci.nsIFile);

   hiddenUnixFile = tmpDir.clone();

   hiddenUnixFile.append(".foo");

   // we don't care if this already exists because we don't care

   // about the file's contents (just the name)

   if (!hiddenUnixFile.exists())

     hiddenUnixFile.create(Ci.nsIFile.NORMAL_FILE_TYPE, 0666);

   return hiddenUnixFile.exists();

 }

 function run_test() {

   // Skip this test on Windows

   if (isWin)

     return;

   do_check_true(createUNIXHiddenFile());

   do_check_true(hiddenUnixFile.isHidden());

 }