Rotate a file that's open and being written at all times

Bruno Polaco asked:

I have an linux application that continually writes logging information into a log file, eg. /var/log/application.log. As the application does not rotate the file automatically, this log file can reach a size of gigabytes in some weeks, so I want to be able to rotate this file properly

My main concern here is that to rotate a file that is opened by the application at all times, I will probably need to:

  1. Move the file to its rotated form /var/log/application.log -> /var/log/application.log.2013-01-28

  2. Create an empty /var/log/application.log. Obs: At this point the application process is still writing to /var/log/application.log.2013-01-28

  3. Change the file descriptor of the application process to point back again to /var/log/application.log

So, am I right? If so, how can i do this? (mainly the changing the file descriptor part)

If i am not, what is the correct way and how to do it?

My answer:

Most such applications respond to a signal, such as SIGHUP, and will close and reopen their log files on receipt of the signal. Check your application’s documentation for the correct signal to send.

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