IpAliases Script (checks and turns on ipaliases on failure)

DWHS.net,

I didn't get that error. I did, however, have to make minor modifications
1) the second log message on line 16 needs to go to "/var/log/" not "logs"
2) On line 17, there was a return character between the email subject and the recipient email address, which cause mail to complain that I didn't have a send-to argument. The return/newline character may have been an artifact of the forum code block.

The only thing that I can think of, other than a similar cut/paste artifact, would be if /bin/sh is aliased to a different shell that is not properly interpreting the IF statement or the test block.

It looks pretty vanilla to me; I would think that any Bourne/Korn (sh/bash/ksh) based shells would be able to handle it fine. If you have a C based shell (csh/tcsh), however, you might consider rewriting the script. That is, I believe there's:
A) 'then' is not preceded with a semi-colon in the IF statement structure
B) redirects are handled differently.

If this is the case, one solution is just change the shebang line to '#!/bin/bash'. If you're running FreeBSD, you may have to install it yourself (and the exact location will possibly be in /usr/local/bin or /usr/bin). Last time I checked, tcsh was the default shell for FreeBSD.

Regards,
-DavidN

 

The following is an adaptation of the above script that does basically the same thing, but cleaned up a bit:

PHP:

#!/bin/sh

#
# Functions
#
add_date() {
  while IFS= read -r line; do
    echo "`date` $line"
  done
}

is_it_up() {
  /bin/ping -W1 -c1 $1 >/dev/null 2>&1
}


#
# Variables
#
email=YOUR_EMAIL_ADDRESS
log_file=/var/log/ip_checker.log
ip=192.168.1.1
ip_is_down_msg="$ip is still down after restarting ipaliases"
wait_period=10


#
# Main program
#
echo "Checking to see if $ip is up" |add_date >>$log_file

if `is_it_up $ip`
then
  echo "$ip is detected as up" |add_date >>$log_file
else
  service ipaliases restart >/dev/null 2>&1
  echo "$ip detected as down" |add_date >>$log_file

  # Check again after $wait_period seconds and send alert if ipaliases is still down
  sleep $wait_period
  if `is_it_up $ip`
  then
    echo "$ip back up after restarting ipaliases" |add_date >>$log_file
  else
    echo "$ip_is_down_msg" |add_date >>$log_file
    echo "$ip_is_down_msg (no icmp echo responses)" |mail -s "IP checker detected down ip" $email
  fi
fi