[SOLVED] how to run a script every second in linux

dinakumar12 · 03-18-2011, 08:52 AM

Hi all,

I want to run a script every second in linux,but cron allows only to run every minute.

so i googled it and found that it can be run like daemon process.

But i dont know how to do that.Kindly post your suggestions please.

The purpose of my script is to check the space of a folder, and this needs to be run every second.

Thanks in advance,
Dinesh.

druuna · 03-18-2011, 08:54 AM

Hi,

Why not write a script that has a loop, which includes a sleep 1?

Hope this helps.

dinakumar12 · 03-18-2011, 09:03 AM

Hi,

can you help me out in this since i dont have much knowledge in this.

i want this command to be executed every second. "/root/script".

druuna · 03-18-2011, 09:10 AM

Hi,

The following is a rough example:

Code:

#!/bin/bash

while [ true ]
do
  commands go here
  sleep 1
done

The bold part is where your code is placed (probably the content of /root/script).

Once you start this script it will execute the bold part, then wait 1 second (the sleep 1) and start again.

For example: The following will show the size of your home directory, every second

Code:

#!/bin/bash

while [ true ]
do
  du -sh ~
  sleep 1
done

Without knowing what the content of /root/script is I cannot help you any further at this moment.

Hope this helps.

dinakumar12 · 03-18-2011, 09:26 AM

Hi druna,

Thanks for your reply. this is my script.

#!/bin/bash
CATALINA_HOME=/usr/local/apache-tomcat-6.0.18/webapps
ls /root/size/200mb > 200limit
for var in $(cut -f1 200limit)
do
#echo $var
cd $CATALINA_HOME
a=`du -sh $var | cut -f1`
echo $a > file
sed -i 's/M//g' file
b=`cut -f1 file`
if [ $b -ge 200 ]
then
cd $CATALINA_HOME/$var
chattr +i ApplicantsAttachments/
chattr +i CallogAttachments/
chattr +i ClientSubmissionAttachments/
chattr +i ImportResumeFolder/
chattr +i ImportResumeTemp/
chattr +i OnBoardedAttachment/
chattr +i RequirementAttachment/
chattr +i TempAttach
else
echo size for $var is lessthan 200M
fi
done

I run this script because our client use to upload documents in our server through our webapplication. But once they reach their 200mb limit they should not upload documents anymore.

I could not use LVM concept since my 90% of server disk size is allotted to root.

so i thought of changing the folder permission once it reaches 200 mb and thats why i need to run my script every second.

But i have one doubt, how to make your script to run in background. shall i run it using cron.

druuna · 03-18-2011, 09:38 AM

Hi,

This should work:

Code:

#!/bin/bash

while [ true ]
do
  CATALINA_HOME=/usr/local/apache-tomcat-6.0.18/webapps
  ls /root/size/200mb > 200limit
  for var in $(cut -f1 200limit)
  do
    #echo $var
    cd $CATALINA_HOME
    a=`du -sh $var | cut -f1`
    echo $a > file
    sed -i 's/M//g' file
    b=`cut -f1 file`
    if [ $b -ge 200 ]
    then
      cd $CATALINA_HOME/$var
      chattr +i ApplicantsAttachments/
      chattr +i CallogAttachments/
      chattr +i ClientSubmissionAttachments/
      chattr +i ImportResumeFolder/
      chattr +i ImportResumeTemp/
      chattr +i OnBoardedAttachment/
      chattr +i RequirementAttachment/
      chattr +i TempAttach
    else
      echo size for $var is lessthan 200M
    fi
  done
  sleep 1
done

Quote:

But i have one doubt, how to make your script to run in background. shall i run it using cron.

I see you use Cent OS, which has an rc.local file (/etc/rc.d/rc.local if I remember correctly). When you add the full path and script name (/full/path/to/script.sh) to this file it will be started when you boot your machine. The while [ true ] part makes sure this script keeps running.

Hope this helps.

dinakumar12 · 03-18-2011, 10:36 AM

hi,

I have included this in /etc.rc.local file

/root/script.

But system not got booted so i booted through single user mode and remove that entry in /etc/rc.local then my system booted.

Do we have anyother option other than this

druuna · 03-18-2011, 11:08 AM

Hi,

I forgot to mention something important.....

You need to add an ampersand (&) after the script line in /etc/rc.d/rc.local file. I.e:

Code:

/root/script.sh &

Sorry about that!

sleddog · 03-18-2011, 08:01 PM

If you're going to run that every second then I'd suggest you work to streamline it. There are several file reads/writes which could be eliminated -- just process the data in memory variables. And you could probably drop the use of sed simply by getting usage in 1M blocks (du -m).

dinakumar12 · 03-19-2011, 06:42 AM

Hi druuna,

Thanks that works.

Thanks to sleddog too for your suggestion.