I learnt how to concatenate an array of strings in bash using ChatGPT.

To declare an array of strings in bash, you can write it following way:

ARRAY_STRINGS=(
    "APPLE"
    "BANANA"
    "FIG"
    "ORANGE"
    "PINEAPPLE"
    "STRAWBERRY"
)

If you echo ARRAY_STRINGS, the output will be only APPLE. To print the entire array, you can write the following code:

echo "${ARRAY_STRINGS[*]}"

# It will print
#
# APPLE BANANA FIG ORANGE PINEAPPLE STRAWBERRY

[*] notation expands the entire array and then substitutes all the words in echo. That’s how we are able to print the whole array. This can also be used to iteration.

for element in "${ARRAY_STRINGS[*]}"; do
    echo "$element"
done

What if we want to concatenate strings with commas or some other character. You can use IFS (internal field separator). It is an environment variable in bash that controls string splits into words or how strings concatenate in command substitution. In this case when array is substituted in using [*], elements are joined by the first character of IFS.

original_ifs=$IFS
IFS=","

echo "${ARRAY_STRINGS[*]}"

IFS=$original_ifs

# It will print
#
# APPLE,BANANA,FIG,ORANGE,PINEAPPLE,STRAWBERRY

Context: I encountered this problem when writing google cloud functions deploy command. I have to pass a more than 5 secrets to this and the command was super long. I refactored it using an array of strings and environment variables in bash.