Iterate through array given as argument to function in shell script

Question

I'm having issues with iterating through an array passed as an argument to a function in my bash script. I thought the answer to this question would solve my issue, but I'm getting a different error and the question is very old, so I thought I should ask a new question.

I am trying to convert this code to a function, so I can pass different parameters:

EX='WT'
declare -a SCN=('fq1' 
'fq2'
'fq3' )

for i in "${SCN[@]}"; do
    echo $i
    echo $EX'_'$i
done

This prints

fq1
WT_fq1  
fq2  
WT_fq2  
fq3  
WT_fq3

What I have tried:

function myfx(){
echo $1
MYNOR=("${!2}")
for i in ${MYNOR[@]}; do
    echo $i
    echo $1'_'$i
done
}
myfx $EX $SCN[@]

Unfortunately, all I get from this is

WT

It doesn't seem to be executing the statements within the loop.

@ArifBurhan Not in this construct: ${!a}. In it, it is an indirect reference If the first character of parameter is an exclamation point (!), it introduces a level of variable indirection. — user2350426
– user2350426, Commented Mar 2, 2016 at 4:13

user2350426 · Accepted Answer · 2016-03-02 04:02:44Z

One way to get the function working is to do this:

function myfx(){
    echo "\$1=$1 \$2=$2"
    b=$2'[@]'
    for i in "${!b}"; do
        echo "$i"
        echo "$1_$i"
    done
}

myfx "$EX" "SCN"

Note that the function is called with the value of $EX and a label SCN.

Inside the function that label is used to build an indirect token b=$2'[@]'.

Then, the indirect token is used to generate the list of values inside SCN.
Using the indirection of bash ${!b}.

A little more complex option is to use only labels to call the function:

    function myfx(){
    echo "\$1=$1 \$2=$2"
    a=${!1}
    b=$2'[@]'
    for i in "${!b}"; do
        echo "$i"
        echo "${a}_$i"
    done
}

myfx "EX" "SCN"

The only added complexity is the need for indirection on $EX.

But probably the simplest of solutions is to pass all the arguments needed:

function myfx(){
    echo "\$1=$1 \$2=$2"
    a=$1; shift
    for i do
        echo "$i"
        echo "${a}_$i"
    done
}

myfx "$EX" "${SCN[@]}"

The simple for i will iterate over all arguments, which after the shift on the line above, will be all the values of "${SCN[@]}".

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