Qfyilyi

I'm trying to set up a "check if machines are online" script with Bash, but running into an issue of when and where to define the variables so they're expanded properly. Something like:

#!/bin/bash

rm01="c01 c02 c03"

rm02="d01 d02 d03"

rm10="e11 e22 e33"

for room in rm01 rm02 rm03; do

    echo $room

    for computer in $room; do

        #run various nslookup/ping tests and report

    done

done

exit 0

I'm running into issues because I can't find a way to expand $room for its corresponding set of computers (in $rm01, $rm02, $rm10) listed at the beginning.

What am I doing wrong?

The quick fix is to use variable indirection:

for computer in ${!room}; do

Relying on word splitting is rarely the best idea, though. You could use arrays and namerefs instead (requires Bash 4.3 or newer):

#!/usr/bin/env bash



# Declare arrays

rm01=(c01 c02 c03)

rm02=(d01 d02 d03)

rm03=(e11 e22 e33)



# Declare room as nameref

declare -n room



# Using nameref as control variable sets room as reference to each variable in turn

for room in rm{01..03}; do

    # Properly quoted array expansion

    for computer in "${room[@]}"; do

        echo "$computer"   # or whatever needs to be done

    done

done

exit 0