MacOS – ntpd unable to create socket on en0

While I suspect that this is not what you want to do, you could always do something like schedule a maintenance task to run to limit the size of the file.

Something like this in a shell script that you schedule:

tail -n 10000 /var/log/DiagnosticMessages > /var/log/DiagnosticMessages

Or if you want to keep a history of the contents, something like this:

mv /var/log/DiagnosticMessages /var/log/DiagnosticMessages_$(date +%y%m%d)

If you want to get fancy, you could:

cat /var/log/DiagnosticMessages | wc -l

and then only rename the file if > 10K. As usual it all depends on how much effort you want to put into it, and whether or not you want a history of this file.

And as you said....this doesn't actually resolve the root cause.

The command grep -v allows filtering out a term or regex from the input. You can use a pipe (|) to combine multiple grep -v commands.

Example: grep -v firewall /var/log/system.log | grep -v imagent | grep -v mdworker

The first grep command in this example operates on the file contents; the subsequent grep commands operate on the output of the previous grep command.

grep is located at /usr/bin/grep on my Lion system. For more information on using grep, read the man page with the command man 1 grep or just man grep.

Edit: Command line can be shortened to

grep -v 'firewall\|imagent\|mdworker' /var/log/system.log