Bash scripting Array concepts

Question

I have two separate lists. One contains 1000 hostnames and other contains 1000 associated IP's for that hosts. I need to generate config entries and push to my config file to add all hosts under our monitoring environment.

    #!/bin/bash
    Enter the hostnames
    readarray hosts
    Enter the IP's
    readarray IP

How should I iterate one by one in a loop like below? I know how to iterate single array by using for i in "${hosts[@]}", but in the case of two separate lists, how to achieve iteration?

    echo -e "\nObject host \""$hosts"\"{"
    import = \""generic-service"\"
    address = \""$IP"\"
    group = \""Mom1-Ping"\" 
    "\n}" >> /etc/icinga2/zones.d/mom2/AP.conf

Example of first list (List 1):

sjc02-mfg-api01.example.com 
sjc02-mfg-api02.example.com
sjc02-mfg-api03.example.com

upto 1000 hosts

Example of second list (List 2):

10.20.2.22 
10.20.2.23 
10.20.2.24

up to to 1000 IP's

Expected output:

     Object host "sjc02-mfg-api01.example.com" {
     import = "generic-service"
     address = "10.20.2.22"
     group = "Mom01-Ping"
     }

     Object host "sjc02-mfg-api02.example.com" {
     import = "generic-service"
     address = "10.20.2.23"
     group = "Mom01-Ping"
     }

     Object host "sjc02-mfg-api03.example.com" {
     import = "generic-service"
     address = "10.20.2.24"
     group = "Mom01-Ping"
     }

     ..........like this I need to generate to all 1000 hosts.............

Answer 1

Combine your both lists together using paste. You can do it as follows:

#!/bin/bash
paste list1 list2 | while IFS=$'\t' read -r L1 L2    
do
echo "
Object host ${L1} {
     import = "generic-service"
     address = ${L2}
     group = "Mom01-Ping"
     }"   
done 

output:

Object host sjc02-mfg-api01.example.com  {
     import = generic-service
     address = 10.20.2.22 
     group = Mom01-Ping
     }

Object host sjc02-mfg-api02.example.com {
     import = generic-service
     address = 10.20.2.23 
     group = Mom01-Ping
     }

Object host sjc02-mfg-api03.example.com {
     import = generic-service
     address = 10.20.2.24
     group = Mom01-Ping
     }

Answer 2

You can iterate over the indices of the pair of arrays:

a1=(foo bar baz)
a2=(one two three)

for ((i=0; i < "${#a1[@]}"; i++)); do 
    echo "${a1[i]} => ${a2[i]}"
done

where ${#a1[@]} is the size of the a1 array