Backup then truncate log file

PsYc0TIC · 10-16-2011, 11:49 AM

Okay... I have been searching and searching to no avail on what I am specifically looking for but here goes

I have a log file (several log files in several locations) that I was to backup and then truncate because they get big fast and once a week I want to just click a bash script to do the above task

Say the log is in /home/widget/log/x.log
and I want to back it up to /home/logs/<log name with current date on it>.log
and then truncate the original x.log leaving the filename intact

I tried this for the truncate:

Code:

#!/bin/bash
cat /dev/null >|  /home/widget/log/x.log

and that works just fine

I tried this for a backup of file:

Code:

#!/bin/bash
SRCD="/home/widget/log/x.log"
TGTD=" /home/logs/<log name with current date on it>.log
OF=.-$(date +%Y%m%d).tgz
tar -cZf $TGTD$OF $SRCD

and it creates a file in the desired dir but it is empty and I do not want a tar file I was the same file type it started as (but as I said this only creates an empty file and doesn't backup the original log file)

I am pretty new to linux and any help would be appreciated

A script that contained the back feature and the tuncate feature following would help me a lot. I have several different ones I need to just change the original log location and destination paths for and I will later set up my cron job to perform this automatically.

Thank you in advance for your help

P.S. I use CentOS 5.7

unSpawn · 10-16-2011, 12:03 PM

Is there a reason why you can't use logrotate?

PsYc0TIC · 10-16-2011, 12:25 PM

logrotate will not allow me to set the original log file location to different places. I have 5 logs in different places plus logrotate will not truncate after backup.

PsYc0TIC · 10-16-2011, 04:06 PM

okay I got the backup code working now and I guess it is okay that it is an archived file for space reasons but will this work for backup then truncate:

Code:

#!/bin/bash
SRCD="/home/widget/log/x.log"
TGTD=" /home/logs/"
OF=backup-$(date +%Y%m%d).tgz
tar czf $TGTD$OF $SRCD
cat /dev/null >| /home/widget/log/x.log

or is there something I need to put in between"

Code:

tar czf $TGTD$OF $SRCD

and

Code:

cat /dev/null >| /home/widget/log/x.log

for some kind of short pause... I don't know and I don't want to run this until I get an opinion on whether it is correct or not

thanks again in advance for the help

unSpawn · 10-16-2011, 04:54 PM

In BASH just

Code:

$>/home/widget/log/x.log

but note that the application using the log file should be stopped to allow it to close its open file descriptors or the log file will remain open and growing.

PsYc0TIC · 10-16-2011, 05:13 PM

Quote:

Originally Posted by unSpawn

In BASH just

Code:

$>/home/widget/log/x.log

but note that the application using the log file should be stopped to allow it to close its open file descriptors or the log file will remain open and growing.

I don't understand

my truncate script truncates just fine... my backup script works just fine (all without stopping the program generating the log) and the log needs to remain open since it is a log after all

will my script above work or is there something that need to go between the last two lines to give a slight pause?

unSpawn · 10-16-2011, 06:27 PM

Quote:

Originally Posted by PsYc0TIC

will my script above work (..)?

If it works for you, fine, if it doesn't just revisit the thread.

PsYc0TIC · 10-16-2011, 07:15 PM

it didn't truncate but it did backup so this is incorrect.

how about this.... I have the two scripts that work independently.. how about what would need to be in a seperate script that calls the backup script, waits 3 seconds, then calls the truncate script?

it is okay to lose 3 seconds of log data

PsYc0TIC · 10-16-2011, 09:52 PM

never mind I figured it out

unSpawn · 10-17-2011, 01:30 AM

Quote:

Originally Posted by PsYc0TIC

never mind I figured it out

So what was it then?

PsYc0TIC · 10-17-2011, 04:22 AM

well not that everyone was so eager to help me but it was a simple answer to my question.... remember when I asked if anything needed to go between the last two lines? The answer would have been a simple "yes and you need to combine the last two separated by &&"

like this:

Code:

#!/bin/bash
SRCD="/home/urt/.q3a/q3ut4/games.log"
TGTD="/root/Desktop/CTF_Logs/"
OF=ctflog-$(date +%Y%m%d).tgz
tar czf $TGTD$OF $SRCD && cat /dev/null >| /home/urt/.q3a/q3ut4/games.log

PsYc0TIC · 10-17-2011, 04:25 AM

my original question still remains.... how can I make it backup the file as a .log rather than turning it into an archive?

What would this part need to be changed to to leave the file extension intact? (I am not concerned about space as I have loads of it)

Code:

OF=ctflog-$(date +%Y%m%d).tgz
tar czf $TGTD$OF $SRCD

unSpawn · 10-17-2011, 11:06 AM

Quote:

Originally Posted by PsYc0TIC

how can I make it backup the file as a .log rather than turning it into an archive?

By not using tar. Copy following as "rotatelog":

Code:

#!/bin/bash
progn=${0//*\//}
__help() { echo "${progn}: [ -f file -d dest_dir ]"; exit 1; }
[ $# -ne 4 ] && __help
while getopts f:d:h OPT; do case "${OPT}" in
 f) [ -f "${OPTARG}" ] || { echo "No file \"${OPTARG}\", exiting." 1>&2; exit 1; }
    SOURCE="${OPTARG}";;
 d) [ -d "${OPTARG}" ] || { echo "No directory \"${OPTARG}\", exiting." 1>&2; exit 1; }
    DSTDIR="${OPTARG}";;
 h|*) __help;; esac; done
DSTDATE="$(/bin/date +'-%Y%m%d')"; DSTNAME="${SOURCE//*\//}"
[ "${DSTNAME}" != "${DSTNAME//.*/}" ] \
&& { EXT="${DSTNAME//*./}"; DSTNAME="${DSTNAME//.*/}${DSTDATE}.${EXT}"; } \
|| { DSTNAME="${DTSNAME}${DSTDATE}"; }
/bin/cp -p "${SOURCE}" "${DSTDIR}/${DSTNAME}" \
|| echo "Copying of ${SOURCE} to ${DSTDIR}/${DSTNAME} failed." 1>&2
exit 0

...and try 'rotatelog -f /home/urt/.q3a/q3ut4/games.log -d /var/tmp' (never save logs in / or /root).

PsYc0TIC · 10-17-2011, 07:54 PM

wow that was a lot of code for a simple task

never mind... I figured that one out too

one line is all it took

Code:

cp  $TGTD$OF

instead of:

Code:

tar czf $TGTD$OF $SRCD

fixed the file extension thing so I don't have to have it archived