How to add default array parameter to bash script

Question

I am trying to pass an array of strings to my bash script that I want to iterate over. I want to set a default array in case the user does not provide this argument to the script.

This is what I have tried:

test.sh:

default_dirs=("x" "y")
dirs=("${1[@]:-${default_dirs[@]}}")
for directory in "${dirs[@]}"
do
    echo "$directory"
done

but running ./test.sh or

./test.sh "w" "z" yields:

./test.sh: line 2: ${1[@]:-${default_dirs[@]}}: bad substitution

What should I do differently?

(( ${#dirs[@]} )) || dirs=("${default_dirs[@]}") is one way. — Jetchisel
– Jetchisel, Commented Jun 26, 2020 at 10:54
dirs=("${dirs[@]:-"${default_dirs[@]}"}") might be what you wanted. — Jetchisel
– Jetchisel, Commented Jun 26, 2020 at 11:09
@cbakos : You can not pass arrays to child processes. Even ./test.sh w z invokes the script not with one array parameter, but with two parameters (w and z). It is just that inside the script, you can alternatively access all parameters passed via the special array named @. Note however, that @ does not behave in every respect like a bash array. — user1934428
– user1934428, Commented Jun 26, 2020 at 12:00

Ted Lyngmo · Accepted Answer · 2020-06-26 13:48:27Z

2

The arguments to the script don't all come in $1 (and $1 isn't an array which is why the substitution fails), so use $@ instead:

dirs=("${@:-${default_dirs[@]}}")
for directory in "${dirs[@]}"
do
    echo "$directory"
done

edited Jun 26, 2020 at 13:48

answered Jun 26, 2020 at 10:38

Ted Lyngmo

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Comments

petrosmm · Accepted Answer · 2024-09-09 14:41:29Z

0

files=(".env.test" ".env")

files_default=(".env.default")
files=("${files[@]:-${files_default[@]}}")

for key in "${files[@]}"; do
    echo "file: $key"
done

comment and uncomment first line and see the result with each...

answered Sep 9, 2024 at 14:41

petrosmm

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