how to implement logrotate in shell script

Question

test.sh

#!/bin/bash
echo "Hello World"

test2.sh

#!/bin/bash
while true
do
    sh test.sh >> /script_logs/test.log &
done

I want to implement logrotate to control the log file size, so how to implement the logrotate, if the situation is like above?

Answer 1

how about using savelog?

It's available in debian and RH and pretty much every other linux distro I know of. It's a /bin/sh shell script, so should run on any other unix too.

e.g. before writing anything to test.log run savelog -n -c 7 test.log. This will keep the 7 most recent non-empty versions of test.log. By default, it will compress rotated logs (but that can be disabled with -l).

If you need to, you can check the size of test.log and only savelog it if it is over a certain size.

Answer 2

#!/bin/bash 
touch /script_logs/test.log
MaxFileSize=2048
while true
do
     sh test.sh >> /script_logs/test.log
#Get size in bytes** 
    file_size=`du -b /script_logs/test.log | tr -s '\t' ' ' | cut -d' ' -f1`
    if [ $file_size -gt $MaxFileSize ];then   
        timestamp=`date +%s`
        mv /script_logs/test.log /script_logs/test.log.$timestamp
        touch /script_logs/test.log
    fi

done

I have removed the "&" as it may cause an issue.

Answer 3

I wrote a logrotee this weekend. I probably wouldn't if I've read @JdeBP's great answer about multilog.

I focused on it being lightweight and being able to bzip2 its output chunks like:

verbosecommand | logrotee \
  --compress "bzip2 {}" --compress-suffix .bz2 \
  /var/log/verbosecommand.log

There's a lot of to be done and tested yet, though.

Answer 4

below script can be used

#!/bin/sh

# Log directory
LOGDIR=/data/logs

# Maximum number of archive logs to keep
MAXNUM=30

#Log files to be handled in that log directory 
files=(access.log error.log)

for LOGFILE in "${files[@]}"
do 

## Check if the last log archive exists and delete it.
if [ -f $LOGDIR/$LOGFILE.$MAXNUM.gz ]; then
rm $LOGDIR/$LOGFILE.$MAXNUM.gz
fi

NUM=$(($MAXNUM - 1))

## Check the previous log file.
while [ $NUM -ge 0 ]
do
NUM1=$(($NUM + 1))
if [ -f $LOGDIR/$LOGFILE.$NUM.gz ]; then
mv $LOGDIR/$LOGFILE.$NUM.gz $LOGDIR/$LOGFILE.$NUM1.gz
fi

NUM=$(($NUM - 1))
done


# Compress and clear the log file
if [ -f $LOGDIR/$LOGFILE ]; then
cat $LOGDIR/$LOGFILE | gzip > $LOGDIR/$LOGFILE.0.gz
cat /dev/null > $LOGDIR/$LOGFILE
fi

done

Answer 5

As I cannot yet add comments to the accepted answer, a BusyBox hint, where du does not have a -b flag:

du /var/log/file | tr -s '\t' ' ' | cut -d' ' -f1

Answer 6

savelog is good, but I would prefer to have a tool that rotate the log according to date, and it doesn't change the extension of the file:

rotatelog -c 30 program.log

1, if the program.log is not created today, then rename it to program.20221219.log (assume today is 20221219. Assume there is no such file exists yet). 1.1, if the program.log is created today, leave it as is.

2, remove all program.xxx.log that are older than 30 days old.

If I add a cronjob to execute the current savelog once every day, it would be very close to what I am thinking to have, but the filename keep changing, and I don't like it.