Question

I am currently trying to simplify a script. Instead of manually entering a host name for each command, I’d like to be able to use variables? arrays? of some sort. Was wondering if you can help.

Example:

hostname1=192.168.1.1
hostname2=192.168.1.2

echo "What would you like to do?"
echo "(1)Ping Hosts"
echo "(2)mkdir /tmp/test"
echo "(3)write to test.txt"
read num_variable

if num_variable = 1
then
ping hostname1
ping hostname2

if num_variable = 2 
ssh -n hostname1 "mkdir /tmp/test"
ssh -n hostname2 "mkdir /tmp/test"

if num_variable = 3
ssh -n hostname1 "echo 'hello' > /tmp/test/test.txt"
ssh -n hostname2 "echo 'hello' > /tmp/test/test.txt"

“Is there an easier way to write this?”

Example:

Hosts=hostname1,hostname2

Commands here?

I’d hate to have 20,000 lines when all i could do is list the hostnames on top and for each num variable execute all of the commands below for the hosts listed in that particular section.

Answer 1

Create an array:

hosts=(hostname1 hostname2 hostname3)

You can split it to multiple lines:

hosts=(
        hostname1 
        hostname2 
        hostname3
      )

Iterate over the elements:

for host in "${hosts[@]}"
do
    echo "$host"
done

Access a particular host:

echo "${hosts[2]}"

Use the select command to create a menu:

PS3='Please enter your choice: '
options=("Option 1" "Option 2" "Option3" "Quit")
select opt in "${options[@]}"
do
    echo "Opt: $opt, Reply: $REPLY"
    case $opt in
        "Option 1")
            echo "you chose choice 1"
            ;;
        "Option 2")
            echo "you chose choice 2"
            ;;
        "Option 2")
            echo "you chose choice 3"
            ;;
        "Quit")
            break
            ;;
        *) echo invalid option;;
    esac
done