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This loops over values. To loop over keys, use "${!array[@]}".
Plus companion warning [[SC2303]]: i is an array value, not a key. Use directly or loop over keys instead.
Problematic code
array=(foo bar)
for i in "${array[@]}"
do
echo "Value is ${array[$i]}"
done
Correct code
Either loop over values
for i in "${array[@]}"
do
echo "Value is $i"
done
or loop over keys:
for i in "${!array[@]}"
do
echo "Key is $i"
echo "Value is ${array[$i]}"
done
Rationale
ShellCheck found a for loop over array values, where the variable is used as an array key.
In the problematic example, the loop will print Value is foo twice. On the second iteration, i=bar, and bar is unset and considered zero, so ${array[$i]} becomes ${array[bar]} becomes ${array[0]} becomes foo.
If you don't care about the key, simply loop over array values and use $i to refer to the array value, like in the first correct example.
If you do want the key, loop over array keys with "${!array[@]}", use $i to refer to the array key, and ${array[$i]} to refer to the array value.
Exceptions
If you do want to use values from the arrays as keys in the same array, you can [[ignore]] these messages with a directive:
declare -A fatherOf=(
["Eric Bloodaxe"]="Harald Fairhair"
["Harald Fairhair"]="Halfdan the Black"
["Halfdan the Black"]="Gudrød the Hunter"
["Gudrød the Hunter"]="Halfdan the Mild"
)
# shellcheck disable=SC2302,SC23203
for i in "${fatherOf[@]}"
do
echo "${fatherOf[$i]:-(missing)} begat $i"
done
Related resources
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