Need help understanding a script!

[Halo]

I know these forums probably see a lot of this, but I'm trying to understand a little more about what's going on in this particular shell script.

It's mostly just for the sake of my curiosity--I've never really touched anything in Linux before, but I stumbled across this script helping a friend find some resources to cite for a paper he's writing, and I was surprised at how much of it I understood, but my limited knowledge of shell scripting has left me scratching my head at some of this stuff. Anyway, if someone could help me break this down, I would appreciate that:

# add ip / hostname separated by while space
HOSTS="cyberciti.biz theos.in router"

I pretty much understand that this is the host I want to ping. What are the parameters? Can the host include IP addresses? What all can I lump into the field?

# no ping request
COUNT=1

This I don't really understand at all . . .

# email report when
SUBJECT="Ping failed"
EMAILID="me@mydomain.com"

This much is pretty much obvious . . . obviously, it's the body of the script that I'm having trouble understanding the most.

for myHost in $HOSTS
do
  count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
  if [ $count -eq 0 ]; then
    # 100% failed
    echo "Host : $myHost is down (ping failed) at $(date)" | mail -s "$SUBJECT" $EMAILID
  fi
done

Is anyone willing to break this down for me line by line? I don't mean to be a pain here, but I really appreciate and respect the time you guys put into these forums.

[i92guboj]

# add ip / hostname separated by while space
HOSTS="cyberciti.biz theos.in router"

I pretty much understand that this is the host I want to ping. What are the parameters? Can the host include IP addresses? What all can I lump into the field?

# no ping request
COUNT=1

This I don't really understand at all . . .

# email report when
SUBJECT="Ping failed"
EMAILID="me@mydomain.com"

This much is pretty much obvious . . . obviously, it's the body of the script that I'm having trouble understanding the most.

All of these are just variables. In bash you set a variable this way:

VAR="foo bar etc whatever"

They have no direct meaning, they could have any other different names like A, B, C or VAR. They only take true meaning when you use them on the script body. So, their contents must be modelled depending on what you are going to do with them. For example, the correct values for HOSTS depends on the use you are going to do of this variable.

If you are going to use it in conjunction with the ping command (man ping for more info), this variable should contain only values that can be parsed and interpreted by ping (so, ip's would be possible as well).

for myHost in $HOSTS
do
  count=$(ping -c $COUNT $myHost | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')
  if [ $count -eq 0 ]; then
    # 100% failed
    echo "Host : $myHost is down (ping failed) at $(date)" | mail -s "$SUBJECT" $EMAILID
  fi
done

Is anyone willing to break this down for me line by line? I don't mean to be a pain here, but I really appreciate and respect the time you guys put into these forums.

This smells like someone's homework (and your nice story seems a bit odd to me), so I am not going to spoil the fun. I will just only tell you that you need to read the awk, ping and bash man pages.

[ghostdog74]

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