The tail -f command doesn't show the file's contents realtime

[ywsswy]

• Windows build number:
  C:\Users\23889>ver

Microsoft Windows [版本 10.0.18362.778]

C:\Users\23889>wsl --list
Ubuntu-20.04 (default)

• What you're doing and what's happening:
  

There is python script which print every second.

#!/usr/bin/env python3

import time
while True:
    print('hello, {}'.format(time.time()), flush=True)
    time.sleep(1)

i run it and redirect the output to file log.log, then use tail -f log.log to see what's happening.

python3 -u output.py >>log.log
tail -f log.log

• What's wrong / what should be happening instead:
  The tail -f command doesn't show the file's contents realtime.

[onomatopellan]

First of all if you want to use Ubuntu 20.04 in WSL1 you need to do this workaraound.
#5125 (comment)

After that try calling your script from a /home folder and not a /mnt/* one.

[ywsswy]

SUCC!

tail -f valid except /mnt/* folder

[therealkenc]

I was able to repro this on 19628 WSL1 on /mnt/c. It's a solid repro (thanks). In the screencap below tail -f does not update as the shell redirect writes (ie, a motion gif would be no better).

My mount line, because it can matter:

Now the damndest thing is a similar bash loop does cause tail -f to work as expected.

while true; do echo $(date) >> log.log; sleep 1; done

Which is all very odd, because the file notifications ought work alright with drvfs. It would take a pretty deep dive to glean what is going on there. What is writing to stdout shouldn't make a whit of difference.

[microsoft-github-policy-service]

This issue has been automatically closed since it has not had any activity for the past year. If you're still experiencing this issue please re-file this as a new issue or feature request.

Thank you!