How to log mysql queries of specific database - Linux - mysql

Question

I have been looking at this post
How can I log "show processlist" when there are more than n queries?
It is working fine by running this command
mysql -uroot -e "show full processlist" | tee plist-$date.log | wc -l
the problem it is overriding the file
I also want to run it in cronjob.
I have added this command to the /var/spool/cron/root:
* * * * * [ $(mysql -uroot -e "show full processlist" | tee plist-`date +%F-%H-%M`.log | wc -l) -lt 51 ] && rm plist-`date +%F-%H-%M`.log
but it is not working. Or maybe it is saving the log file some place out of the root folder.
So my question is: how to temporarily log all queries from specific database and specific table and save the whole queries in 1 file?
Note: it is not slow/long queries log I am looking for, but just temp solution to read which queries are running for a database

Answer 1

solution is:
watch -n 1 "mysqladmin -u root -pXXXXX processlist | grep tablename" | tee -a /root/plist.log

Answer 2

The % character has special meaning in crontab commands, you need to escape them. So you need to do:
* * * * * [ $(mysql -uroot -e "show full processlist" | tee plist-`date +\%F-\%H-\%M`.log | wc -l) -lt 51 ] && rm plist-`date +\%F-\%H-\%M`.log
If you want to use your original command, but not overwrite the file each time, you can use the -a option of tee to append:
mysql -uroot -e "show full processlist" | tee -a plist-$date.log | wc -l
To run the command every second for a minute, write a shell script:
#!/bin/bash
for i in {1..60}; do
[ $(mysql -uroot -e "show full processlist" | tee -a plist.log | wc -l) -lt 51 ] && rm plist.log
sleep 1
done
You can then run this script from cron every minute:
* * * * * /path/to/script
Although if you want to run something continuously like this, cron may not be the best way. You could use /etc/inittab to run the script when the system boots, and it will automatically restart it if it dies for some reason. Then you would just use an infinite loop:
#!/bin/bash
while :; do
[ $(mysql -uroot -e "show full processlist" | tee -a plist.log | wc -l) -lt 51 ] && rm plist.log
sleep 1
done