Bash for loop syntax

Question

I\'m working on getting accustomed to shell scripting and ran across a behavior I found interesting and unexplained. In the following code the first for loop will execute co

Answer 1

Brace expansion occurs before parameter expansion, so you can't use a variable as part of a range.

Expand the array into a list of values:

for letter in "${letters[@]}"; do
    echo "$letter"
done

Or, expand the indices of the array into a list:

for i in ${!letters[@]}; do 
    echo "${letters[i]}"
done

As mentioned in the comments (thanks), these two approaches also accommodate sparse arrays; you can't always assume that an array defines a value for every index between 0 and ${#letters[@]}.