Truncating file based on date Post: 302478346

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Top Forums UNIX for Dummies Questions & Answers Truncating file based on date Post 302478346 by methyl on Tuesday 7th of December 2010 06:03:28 PM

12-07-2010

Registered User

Create a cron which runs daily at midnight and rotates the logs.
Note to "Parm0073" (as explained by "achenle") we never issue "mv logfile" (or "rm logfile") because this will create ghost files if the log is open by a process.

This is the longhand method. It should work whether or not the logfile exists each day and will correctly deal with a logfile which is open by a process.
If you currently have a large logfile, the issue will take 8 days to roll off that logfile. Be patient.

Code:

if [ -f logfile-7 ]
then
    rm logfile-7
fi
if [ -f logfile-6 ]
then
    mv logfile-6 logfile-7
fi
if [ -f logfile-5 ]
then
    mv logfile-5 logfile-6
fi
if [ -f logfile-4 ]
then
    mv logfile-4 logfile-5
fi
if [ -f logfile-3 ]
then
    mv logfile-3 logfile-4
fi
if [ -f logfile-2 ]
then
    mv logfile-2 logfile-3
fi
if [ -f logfile-1 ]
then
    mv logfile-1 logfile-2
fi
cp -p logfile logfile-1
>logfile

Just for interest. Personally I rotate system logs at midday. Though you get two half-days in each log it gives you chance to read what happened after you went home at some time before lunch the next day.

Last edited by methyl; 12-07-2010 at 07:17 PM.. Reason: Assorsted corrections and acknowledgements.

methyl

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LEARN ABOUT DEBIAN

explain_truncate_or_die

explain_truncate_or_die(3)				     Library Functions Manual					explain_truncate_or_die(3)

NAME

       explain_truncate_or_die - truncate a file and report errors

SYNOPSIS

       #include <libexplain/truncate.h>
       void explain_truncate_or_die(const char *pathname, long long length);

DESCRIPTION

       The  explain_truncate_or_die  function  is  used to call the truncate(2) system call.  On failure an explanation will be printed to stderr,
       obtained from explain_truncate(3), and then the process terminates by calling exit(EXIT_FAILURE).

       This function is intended to be used in a fashion similar to the following example:
	      explain_truncate_or_die(pathname, length);

       pathname
	       The pathname, exactly as to be passed to the truncate(2) system call.

       length  The length, exactly as to be passed to the truncate(2) system call.

       Returns:
	       This function only returns on success.  On failure, prints an explanation and exits.

SEE ALSO

       truncate(2)
	       truncate a file to a specified length

       explain_truncate(3)
	       explain truncate(2) errors

       exit(2) terminate the calling process

COPYRIGHT

       libexplain version 0.52
       Copyright (C) 2008 Peter Miller

															explain_truncate_or_die(3)

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