How to empty a personal log file?

For Developers
1

Hi,
i'm running a program and it should keep running 24/7, and ofc i'm saving its outputs in a log file
"programName > logfile"
the thing is, when i try to delete its content and not the file itself since the program is using it. i can't find a way to clean it up, i used:

cat /dev/null > "logfile"
echo "" > "logfile"
> log file
:> logfile
trancate "logfile" -s 0

none of them works, i know about the logrotate but i'm trying to avoid downloading or using any other package beside the one already exist.
i think, the program is writing its output in a buffer and then write it back in the file, so i need to empty that buffer first.
hope you can help me with this.

2

If there's nothing important, you can try to disable logging, or write the log directly to /dev/null, or symlink it to /dev/null.
You can also try sending SIGHUP or other signals to the process, which may help to reload the log or reset the buffer.

3

This what Apache does (or did, in the good old days):

  • Rename the log file externally (the program will continue to use the renamed file, because it is already open).
  • Send a signal to the running program.
  • When the program receives the signal, it just closes and opens again the log file.
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