use writeFileSync instead of echo to clear the logfile

Author: rounak610

lib/Local.js

@@ -37,7 +37,11 @@ function Local(){
 
     const binaryPath = this.getBinaryPath(null, options['bs-host']);
     that.binaryPath = binaryPath;
-    childProcess.exec('echo "" > ' + that.logfile);
+    try {
+      fs.writeFileSync(that.logfile, '');
+    } catch(e) {
+      console.error('Could not clear log file: ', e.message);
+    }
     that.opcode = 'start';
     if(!this.binaryPath){
       return new LocalError('Couldn\'t find binary file');
@@ -86,7 +90,11 @@ function Local(){
 
     this.getBinaryPath(function(binaryPath){
       that.binaryPath = binaryPath;
-      childProcess.exec('echo "" > ' + that.logfile);
+      try {
+        fs.writeFileSync(that.logfile, '');
+      } catch(e) {
+        console.error('Could not clear log file: ', e.message);
+      }
 
       that.opcode = 'start';
       that.tunnel = childProcess.execFile(that.binaryPath, that.getBinaryArgs(), function(error, stdout, stderr){