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tail & tail -F

From tail -F
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tail -F and piping to other commands (configuring buffering of other commands)

If you want to pipe output of tail -F to commands like grep or jq then look into configuring them so they buffer per line rather than holding on to larger buffers, look at the following notes:

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From Use [tail -F] (capital F) instead of [tail -f] when tailing log files.
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#llm.claude-sonnet-4

Key Differences

  • tail -f follows the file descriptor - stops working if file is deleted/rotated
  • tail -F follows the file path - automatically reconnects when file is recreated

Why This Matters for Logs

Log rotation tools (logrotate, etc.) commonly:

  1. Move app.log to app.log.1
  2. Create a new empty app.log
  3. Signal the app to start writing to the new file

With tail -f: You'd be stuck watching the old rotated file With tail -F: Automatically switches to the new file

Bottom Line

# This stops working after log rotation
tail -f /var/log/app.log

# This keeps working through log rotations  
tail -F /var/log/app.log

Always use tail -F for production log monitoring.

Children
  1. tail -F