Array + why arrays are not in the Right place

Question

I set an array named “disks” to the following words - sdb sdc sdd

in bash shell:

declare -A disks
Machine=worker01
disks[$Machine]="sdb sdc sdd"

now we print all words as the following:

echo ${disks[@]}
sdb sdc sdd

now we want to print the first item ( that should be sdb )

echo ${disks[0]}

but no output

the same with:

echo ${disks[1]}

echo ${disks[2]}

also with:

echo ${disks[3]}

echo ${disks[4]}

…

what is wrong here?

also not as:

for i in {1..100}
> do
> echo ${disks[$i]}
> done

so how can I print the first words of the array “disks” - when Machine=worker01

echo ${disks[$Machine]}

Answer 1

You're assigning to disks[worker01], but trying to read from disks[0] etc. The indexes are different.

As someone commented, Bash doesn't have multidimensional arrays, and that's what you really would need here. You can simulate that roughly with with space-separated strings, but then you need to split the string explicitly.

#!/bin/bash

declare -A disks
disks["host1"]="sda sdb"
disks["host2"]="sda sdb sdc"

for m in "${!disks[@]}"; do
    # split the string to array 'd'
    IFS=' ' read -a d <<< "${disks[$m]}"
    printf "$m has disk %s\n" "${d[@]}"
done

Answer 2

Why did you declare Machines when you never use it after?

$ disks=(sdb sdc sdd)
$ echo ${disks[0]}
sdb
$ echo ${disks[1]}
sdc
$ echo ${disks[2]}
sdd

Answer 3

The data is in ${disks[worker01]}, not in ${disks[0]}.

I am also wondering if you are trying to use an array of arrays: An array of machines, each with an array of disks.

Answer 4

if you are looking just to print an specific value you could use:

echo ${disks[$Machine]} | awk '{print $1}'

where $1 = index 0

OUTPUT:

sdb