vi scripts on UNIX

UNIX for Advanced & Expert Users
1

Hi there
I'm hoping one of the expert unix guys or gals can assist me in understanding the language within scripts

e.g

clear
while true
do
tput cup 0 0
        LIST=`grep cisco  /etc/hosts|grep -v _int | awk '{print $2}'`
        for SITE in $LIST
        do
        IP=`grep "$SITE" /etc/hosts | grep -v _int| cut -d" " -f1`
        CN=`grep "$SITE" /etc/hosts | grep -v _int| cut -d" " -f2`
        #echo "$SITE\t loss at  __                              "
        MESS=`ping $SITE -n $1 |grep transmit|cut -d"," -f3|cut -d"%" -f1`
        #echo "^[[A$SITE\t Up at $MESS% "
        if [ $MESS -gt 99 ]
        then
        echo "$SITE\t*is DOWN$MESS% Loss*       $CN              "
        else
        echo "$SITE\t is UP at $MESS% Loss      $CN              "
        fi
        done
sleep 3
clear
done

~

What does this do from the first sting to the last.

Thanks in advance
Marcus

added code tags for readability --oombera

2

the script reads all hostnames that have 'cisco' in it from the /etc/hosts (so we are probably talking routers here) and then performs a 'ping' to see if they are 'alive' or not. This is done every 3 seconds.

3

Thanks for that.

But i need to know the meaning to the commands within this script.

while true =
tput =
CN =
MESS =
cut =
-v =

etc...

is there some place ( links when i can go through all these things )
and start to understand them myself instead of always asking someone

Thanks in advance
Marcus.

4

But i need to know the meaning to the commands within this script.

while true = man true for more info "true, false - provide truth values"
tput = man tput for more info "tput - initialize a terminal or query terminfo database"
CN = just a variable
MESS = just a variable
cut = man cut
grep -v = is a switch for grep. man grep for more info

and so on down the road. look at it this was IF you have

var1=something else. most likely var1 is a variable.
if you have a string of commands IE true, grep, tput, cut, grep......

you can type at a shell prompt: man <i>command-name</i> and it will give you the manual page for said command.

5

Much appreciated.

Have Fun.