SC2302.md

Pattern: Use of for loop over array values

Issue: -

Description

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.

Example of incorrect code:

array=(foo bar)
for i in "${array[@]}"
do
  echo "Value is ${array[$i]}"
done

Example of correct code:

for i in "${array[@]}"
do
  echo "Value is $i"
done

Further Reading

• ShellCheck - SC2302