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I have a process that's writing a lot of data to stdout, which I'm redirecting to a log file. I'd like to limit the size of the file by occasionally copying the current file to a new name and truncating it.
My usual techniques of truncating a file, like
cp /dev/null file don't work, presumably because the process is using it.
Is there some way I can truncate the file? Or delete it and somehow associate the process' stdout with a new file?
FWIW, it's a third party product that I can't modify to change its logging model.
EDIT redirecting over the file seems to have the same issue as the copy above - the file returns to its previous size next time it's written to:
ls -l sample.log ; echo > sample.log ; ls -l sample.log ; sleep 10 ; ls -l sample.log -rw-rw-r-- 1 user group 1291999 Jun 11 2009 sample.log -rw-rw-r-- 1 user group 1 Jun 11 2009 sample.log -rw-rw-r-- 1 user group 1292311 Jun 11 2009 sample.log 
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You can simply truncate a log file using > filename syntax. For example if log file name is /var/log/foo, try > /var/log/foo as root user.
The truncate command is used to shrink or extend the size of a file to the given size. The truncate command cannot remove the file whereas removes the contents of the file and set size of file is zero byte. The meaning of truncate is reducing.
To truncate is to shorten by cutting off. In computer terms, when information is truncated, it is ended abruptly at a certain spot. For example, if a program truncates a field containing the value of pi (3.14159265...) at four decimal places, the field would show 3.1415 as an answer.
As of coreutils 7.0, there is a truncate command.
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