Quelle  script_file.js

/* eslint-env mozilla/chrome-script */

// eslint-disable-next-line mozilla/reject-importGlobalProperties
Cu.importGlobalProperties(["File"]);

addMessageListener("file.open", function () {
  var testFile = Services.dirsvc
    .QueryInterface(Ci.nsIProperties)
    .get("ProfD", Ci.nsIFile);
  testFile.append("ipc_fileReader_testing");
  testFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);

  var outStream = Cc[
    "@mozilla.org/network/file-output-stream;1"
  ].createInstance(Ci.nsIFileOutputStream);
  outStream.init(
    testFile,
    0x02 | 0x08 | 0x20, // write, create, truncate
    0o666,
    0
  );

  var fileData = "Hello World!";
  outStream.write(fileData, fileData.length);
  outStream.close();

  File.createFromNsIFile(testFile).then(function (file) {
    sendAsyncMessage("file.opened", { file });
  });
});

addMessageListener("emptyfile.open", function () {
  var testFile = Services.dirsvc
    .QueryInterface(Ci.nsIProperties)
    .get("ProfD", Ci.nsIFile);
  testFile.append("ipc_fileReader_testing");
  testFile.createUnique(Ci.nsIFile.NORMAL_FILE_TYPE, 0o600);

  var outStream = Cc[
    "@mozilla.org/network/file-output-stream;1"
  ].createInstance(Ci.nsIFileOutputStream);
  outStream.init(
    testFile,
    0x02 | 0x08 | 0x20, // write, create, truncate
    0o666,
    0
  );

  File.createFromNsIFile(testFile).then(function (file) {
    sendAsyncMessage("emptyfile.opened", { file });
  });
});