feat(daemon): add getDaemonProcessId helper

config/daemon/get-daemon-process-id.js

@@ -0,0 +1,17 @@
+// @flow
+import fs from 'fs';
+import path from 'path';
+import { getZcashFolder } from './get-zcash-folder';
+
+const ZCASH_PID_FILE = 'zcashd.pid';
+
+export const getDaemonProcessId = (zcashPath?: string) => {
+  try {
+    const myPath = zcashPath || getZcashFolder();
+    const buffer = fs.readFileSync(path.join(myPath, ZCASH_PID_FILE));
+    const pid = Number(buffer.toString().trim());
+    return pid;
+  } catch (err) {
+    return null;
+  }
+};