Ygtjki

I have the following script that SSH to a server with a key and makes a lot of stuff there.

#!/usr/bin/env bash

ssh -i mykey.pem myuser@SERVER_IP << 'ENDSSH'
[A LOT OF STUFF]
ENDSSH

(which I run it with sh scriptname.sh)

Now I want to to the same in another server, so I've to SSH to two different servers (ip_1 and ip_2) with two different .pem files (mykey1.pem and mykey2.pem).

So far I know how to loop the ips as follows:

#!/usr/bin/env bash

ip_list="ip_1 ip_2"

for ip in $ip_list; do
ssh -i mykey.pem myuser@$ip << 'ENDSSH'
[A LOT OF STUFF]
ENDSSH
done

but now I would like to loop also to get the proper pem file. How can I archieve this? Maybe with another list? Can someone provide me an elegant solution?

• 
  ip_1 should use mykey1.pem
  


• 
  ip_2 should use mykey2.pem
  

Thanks in advance

One way to do it is to use a while IFS=, read -r loop on a csv here-document.

#! /bin/sh -
while IFS=, read <&3 -r ip key; do
 ssh -i "$key" "$ip" << ENDSSH
 ...
ENDSSH
done 3<< ENDCSV
10.0.0.1,p1.pem
10.0.0.2,p2.pem
ENDCSV

Then you don't even need to require users to install bash. If portability is not a concern, you could use zsh instead which supports looping over more than one variable.

#! /usr/bin/env zsh
for ip key (
 10.0.0.1 p1.pem
 10.0.0.2 p2.pem
) ssh -i $key $ip << ENDSSH
 ...
ENDSSH

Since you're using bash, you can use associative arrays:

#!/usr/bin/env bash

declare -A ip_list=(["ip_1"]="mykey1.pem" ["ip_2"]="mykey2.pem")

for ip in "$!ip_list[@]"; do
 ssh -i "$ip_list[$ip]" myuser@"$ip" << 'ENDSSH'
[A LOT OF STUFF]
ENDSSH
done

Note that associative arrays, unlike regular indexed arrays, are not saved in a specific order, so there is no guarantee that ip_1 will be processed before ip_2.

If you need to use a simple, POSIX compatible shell, create a file with the ip and key files, one per line:

$ cat iplist.txt
ip1 mykey1.pem
ip2 mykey2.pem

Then, use this script:

#!/bin/sh

while read -r ip key; do
 ssh -i "$key" myuser@"$ip" << 'ENDSSH'
[A LOT OF STUFF]
ENDSSH
done 

And run it with:

sh /path/to/script < /path/to/iplist.txt

But if you go that route, Stéphane's approach is better.

Your original script can be made slightly more portable via set built-in, plus have ip and key go together as one string, colon separated. We later can use prefix and suffix removal to extract corresponding entry

#!/usr/bin/env bash

# Set positional parameters
# Example ip addresses
set -- 192.168.0.1:mykey1 192.168.1.1:mykey2

# iterating without specifying 'in' assumes positiona parameters
for host; do
 ssh -i $host##*:.pem myuser@$host%%:* << 'ENDSSH'
[A LOT OF STUFF]
ENDSSH

done