Getting wrong value of passed argument to function in bash script

Question

I am writing bash script given below (Please ignore the capital letters variable names, this is just my test file):

#!/bin/bash

create_nodes_directories(){
HOSTS=(192.168.110.165 192.168.110.166 192.168.110.167)
accounts=('accountnum11' 'accountnum12' 'accountnum13')
for i in "${!HOSTS[@]}"; do
        read -r curhost _ < <(hostname -I)
        printf 'Enter the key pair for the %s node\n' "${accounts[i]}"
        printf "Enter public key\n"
        read -r EOS_PUB_KEY
        printf "Enter private key\n"
        read -r EOS_PRIV_KEY
        PRODUCER=${accounts[i]}

        args=()
        args+=("$curhost")

        for j in "${!HOSTS[@]}"; do
                if [[ "$i" != "$j" ]]; then
                        args+=("${HOSTS[$j]}")
                else
                        continue;

                fi
        done
        #echo 'Array before test:'"${args[*]}"
        create_genesis_start_file "$EOS_PUB_KEY" "$EOS_PRIV_KEY" "${HOSTS[$i]}" "$PRODUCER" args
        create_start_file "$EOS_PUB_KEY" "$EOS_PRIV_KEY" "${HOSTS[$i]}" "$PRODUCER" args
done
}
            
create_genesis_start_file(){
        EOS_PUB_KEY=$1
        EOS_PRIV_KEY=$2
        CURRENTHOST=$3
        PRODUCER=$4
        peerags="$5[@]"
        peers=("${!peerags}")

        echo 'Genesis Currenthost is:'"$CURRENTHOST"
        #echo "${peers[*]}"
        VAR=""
        length=${#peers[@]}
        last=$((length - 1))

        for i in "${!peers[@]}" ; do

                if [[ "$i" == "$last" ]]; then
                        VAR+="--p2p-peer-address ${peers[$i]}:8888 \\"
                else
                        VAR+=$"--p2p-peer-address ${peers[$i]}:8888 \\"$'\n\t'
                fi
        done
}

create_start_file(){
        EOS_PUB_KEY=$1
        EOS_PRIV_KEY=$2
        CURRENTHOST=$3
        PRODUCER=$4
        peerags="$5[@]"
        peers=("${!peerags}")

        echo 'Start file Currenthost is:'"$CURRENTHOST"
        #echo "${peers[*]}"
}

create_nodes_directories

For every iteration of the first for loop, I am displaying the third argument $CURRENTHOST which is passed to functions create_genesis_start_file and create_start_file. For first iteration, output is:

Genesis Currenthost is:192.168.110.165
Start file Currenthost is:192.168.110.167

Second iteration:

Genesis Currenthost is:192.168.110.166
Start file Currenthost is:192.168.110.167

Third iteration,

Genesis Currenthost is:192.168.110.167
Start file Currenthost is:192.168.110.167

Genesis Currenthost is as expected and Start file Currenthost should be same with it. I am not getting why the Start file Currenthost is always set as 192.168.110.167. If I remove the below code from create_genesis_start_file it is working fine:

VAR=""
            length=${#peers[@]}
            last=$((length - 1))
    
            for i in "${!peers[@]}" ; do
    
                    if [[ "$i" == "$last" ]]; then
                            VAR+="--p2p-peer-address ${peers[$i]}:8888 \\"
                    else
                            VAR+=$"--p2p-peer-address ${peers[$i]}:8888 \\"$'\n\t'
                    fi
            done

I am not getting the exact problem why the variable value is getting changed? Please help.

You're using the variable i in both the main for i in "${!HOSTS[@]}" loop and also in the create_genesis_start_file function, and the function is stepping on the value partway through the loop. To avoid the conflict, either use a different variable name in the two places, or declare it local in the function (or both). — Gordon Davisson
– Gordon Davisson, Commented Nov 10, 2020 at 7:28

user1934428 · Accepted Answer · 2020-11-10 07:34:39Z

1

The "$5[@]" looks odd to me. You can't use a scalar $5 as if it were an array.

It seems that you want to pass a whole array as parameter. Since bash does not have a native way to do this, I suggest that on the calling side, you pass "${args[@]}" as parameter, and inside your function, you do a

shift 4
peers=( "$@" )

Another possibility, which however violates the idea of encapsulation, is to treet peers as a global variable, which is accessible to all functions. With this approach, you would on the caller side collect the information already in the variable peers instead of args.

From a programming style, global variables (accross function boundaries) are usually disliked for good reasons, but in my personal opinion, if you just do simple shell scripting, I would find it an acceptable solution.

answered Nov 10, 2020 at 7:34

user1934428

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