Append data to a text file without closing/reopening the text file every FixedUpdate()

I am trying to record the coordinates of the position of an object into a text file and my code is working fine and doing what I want. However, the way it is set up will keep opening and closing the file every time it writes a new line which seems unnecessary and hard drive intensive. My code looks like this:

When the key "1" is pressed, collectdata = true for 410 seconds. Writing to the text file begins and then after that amount of time it stops.

Code (CSharp):

1. void Start ()
2.         {
3.             filePath = Path.Combine(Application.dataPath, folderName);
4.             filePath = Path.Combine(filePath, fileName);
5.             textFile = new FileInfo (filePath);
6.         }
7.      
8.  
9.     void FixedUpdate()
10.         {
11.             GameObject ROOMDATA = GameObject.FindGameObjectWithTag ("ROOMDATA");
12.             if (collectData == true)
13.             {
14.                 writer = textFile.AppendText ();
15.                 float x = ROOMDATA.transform.position.x;
16.                 float z = ROOMDATA.transform.position.z;
17.                 writer.WriteLine (x + "\t" + z);
18.                 Debug.Log ("write to file");
19.             writer.close
20.         }
21.          
22.          }
23.  
24.     void Update ()
25.         {
26.         // Pressing 1 saves roomdata1
27.         if (Input.GetKeyDown ("1")) {
28.             collectData = true;
29.             StartCoroutine (WaitAndStop ());
30.             }
31.  
32.         }
33.     IEnumerator WaitAndStop()
34.     {
35.         yield return new WaitForSeconds(410);
36.         collectData = false;
37.  
38.     }
39. }

 

Why do you need to write it every frame ? If there no special reasons, you should store data to a variable, and write the file when WaitAndStop end.

 

That's exactly what I need to do