linux bash shell script - pass through function array variable

Question

So in order to be versatile, I make a lot of functions and i want to define my own variable name when i call on that function. For basic text, numbers it works and this is how I do it

function func_get_device_hostname
{
    local _device_hostname=$1
    local device_hostname2="TEST"
    eval $_device_hostname="'$device_hostname2'"
}

function func_display_device_hostname
{
    func_get_device_hostname device_hostname
    echo $device_hostname
}

but when i use that same method with an array like so

function func_get_vds_ip
{
    func_get_vds_count vds_count
    local _arr_vds_ip=$1
    arr_vds_ip2=()
    i=1
    while [ $i -le $vds_count ]; do
        local arr_vds_ip2+=($(avahi-browse -rvpc vds._tcp | grep "=;" | cut -d ';' -f8 | sed -n $i' p'))
        i=$(($i+1))
    done
    echo ""
    eval $_arr_vds_ip="'$arr_vds_ip2'"
}

function func_display_vds_ip
{
    func_get_vds_ip arr_vds_ip
    echo -n "VDS IP        "
    for i in "${arr_vds_ip[@]}"
    do
        echo -n "$i"
        echo -n " - "
    done
}

I get the following error

line 339: {arr_vds_ip[@]}=192.168.18.82: command not found

line 339 refers to this part of the code

    eval $_arr_vds_ip="'$arr_vds_ip2'"

what is the best method to do this? am i using a wrong command?

glenn jackman · Accepted Answer · 2022-10-21 13:45:01Z

You could be using namerefs (See Shell Parameters and search down for "nameref"). Once you declare a nameref, you just use the local variable like a normal variable, and the contents are reflected in the referenced variable.

For the simple case:

function func_get_device_hostname {
    local -n _device_hostname=$1
    local name=TEST
    _device_hostname=$name
}

testing

$ declare -p foo
bash: declare: foo: not found
$ func_get_device_hostname foo
$ declare -p foo
declare -- foo="TEST"

For the array case:

function func_get_vds_ip {
    local -n _arrname=$1
    local count=10 i
    _arrname=()
    for ((i=1; i<=count; i++)); do
        _arrname+=($RANDOM)
    done
}

testing

$ declare -p bar
bash: declare: bar: not found
$ func_get_vds_ip bar
$ declare -p bar
declare -a bar=([0]="23299" [1]="13876" [2]="24702" [3]="17413" [4]="14999" [5]="16309" [6]="25625" [7]="29001" [8]="7117" [9]="23532")

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