How to log local on microbit?

I have next code:
```python
import time
from microbit import *
def writeToLocalStrage():
with open('log.txt') as old_file:
text_from_file_before = old_file.read()

with open('log.txt', 'w') as my_file:
display.show(text_from_file_before)
content = str(temperature())
content = text_from_file_before + content
content = content + ';'
my_file.write(content)


while True:
writeToLocalStrage()
time.sleep(2)
```

if I want to get it with:
ufs get log.txt
I get only 3x
28;28;28;
but never more then this, is the memory full or my script is not good?