Shell – Log monitoring using shell script

monitoringshell-script

I would like to monitor a log file for errors and then send an email to administrators.

The log file contains data like below

11 Aug 02:30 Service1 restarted
11 Aug 05:35 Service1 restarted
11 Aug 08:43 Service2 restarted
11 Aug 11:20 Service1 restarted
11 Aug 14:53 Service2 restarted

I would like to create a script which runs for every 5 minutes and checks the last occurrence of service restart and send an email.

For example : if the script runs at 02:35 it sees that Service1 restarted so it will send an email like Service1 restarted at 02:30 . Now when the script runs at 5:45 then it should send email that Service1 restarted at 05:35 only (should not include 02:35 restart)

Is there a way to achieve this requirement ? I am basically new to Linux and Shell scripting

Best Answer

Start by making a five minute crontab:

*/5 * * * * myscript.sh

Which runs myscript.sh (in $HOME dir)

 #!/bin/bash
 tail -1 /path/to/file.log > /some/dir/after
 if cmp -s /some/dir/after /some/dire/before
 then
     cat /some/dir/after | mail -s "restart" admin@exemple.com
     cp /some/dir/after /some/dir/before
 fi

With the correct values (of course).

Note that this implies there will not be two restarts within five minutes.

Example

Here I'm connecting to my mail server.

$ echo "QUIT" | nc -w 5 mail.bubba.net 25
220 bubba.net ESMTP Sendmail 8.14.3/8.14.3; Sat, 19 Apr 2014 16:31:44 -0400
221 2.0.0 bubba.net closing connection
$

If you check the status returned by this operation:

$ echo $?
0

However if nothing at the other ends accepts our connection:

$ echo QUIT | nc -w5 localhost 25
Ncat: Connection refused.
$

Checking the status returned from this:

$ echo $?
1

Putting it together

Here's my version of a script called mail_chkr.bash.

#!/bin/bash

echo "Checking Mail Server #1"
echo "QUIT" | nc -w 5 mail.bubba.net 25 > /dev/null 2>&1

if [ $? == 0 ]; then
  echo "mail server #1 is UP"
else
  echo "mail server #1 is DOWN"
fi

echo "Checking Mail Server #2"
echo "QUIT" | nc -w 5 localhost 25 > /dev/null 2>&1

if [ $? == 0 ]; then
  echo "mail server #2 is UP"
else
  echo "mail server #2 is DOWN"
fi

Running it:

$ ./mail_chkr.bash 
Checking Mail Server #1
mail server #1 is UP
Checking Mail Server #2
Ncat: Connection refused.
mail server #2 is DOWN

Best Answer

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Simple script for monitoring a mailserver

Example

Putting it together

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