How to pass an array argument to the Bash script

Question

It is surprising me that I do not find the answer after 1 hour search for this. I would like to pass an array to my script like this:

test.sh argument1 array argument2

I DO NOT want to put this in another bash script like following:

array=(a b c)
for i in "${array[@]}"
do
  test.sh argument1 $i argument2
done

Answer 1

Bash arrays are not "first class values" -- you can't pass them around like one "thing".

Assuming test.sh is a bash script, I would do

#!/bin/bash
arg1=$1; shift
array=( "$@" )
last_idx=$(( ${#array[@]} - 1 ))
arg2=${array[$last_idx]}
unset array[$last_idx]

echo "arg1=$arg1"
echo "arg2=$arg2"
echo "array contains:"
printf "%s\n" "${array[@]}"

And invoke it like

test.sh argument1 "${array[@]}" argument2

Answer 2

Have your script arrArg.sh like this:

#!/bin/bash

arg1="$1"
arg2=("${!2}")
arg3="$3"
arg4=("${!4}")

echo "arg1=$arg1"
echo "arg2 array=${arg2[@]}"
echo "arg2 #elem=${#arg2[@]}"
echo "arg3=$arg3"
echo "arg4 array=${arg4[@]}"
echo "arg4 #elem=${#arg4[@]}"

Now setup your arrays like this in a shell:

arr=(ab 'x y' 123)
arr2=(a1 'a a' bb cc 'it is one')

And pass arguments like this:

. ./arrArg.sh "foo" "arr[@]" "bar" "arr2[@]"

Above script will print:

arg1=foo
arg2 array=ab x y 123
arg2 #elem=3
arg3=bar
arg4 array=a1 a a bb cc it is one
arg4 #elem=5

Note: It might appear weird that I am executing script using . ./script syntax. Note that this is for executing commands of the script in the current shell environment.

Q. Why current shell environment and why not a sub shell?
A. Because bash doesn't export array variables to child processes as documented here by bash author himself

Answer 3

If values have spaces (and as a general rule) I vote for glenn jackman's answer, but I'd simplify it by passing the array as the last argument. After all, it seems that you can't have multiple array arguments, unless you do some complicated logic to detect their boundaries.

So I'd do:

ARRAY=("the first" "the second" "the third")
test.sh argument1 argument2 "${ARRAY[@]}"

which is the same as:

test.sh argument1 argument2 "the first" "the second" "the third"

And in test.sh do:

ARG1="$1"; shift
ARG2="$1"; shift
ARRAY=("$@")

---

If values have no spaces (i.e. they are urls, identifiers, numbers, etc) here's a simpler alternative. This way you can actually have multiple array arguments and it's easy to mix them with normal arguments:

ARRAY1=(one two three)
ARRAY2=(four five)
test.sh argument1 "${ARRAY1[*]}" argument3 "${ARRAY2[*]}" 

which is the same as:

test.sh argument1 "one two three" argument3 "four five"

And in test.sh you do:

ARG1="$1"
ARRAY1=($2) # Note we don't use quotes now
ARG3="$3"
ARRAY2=($4)

I hope this helps. I wrote this to help (you and me) understand how arrays work, and how * an @ work with arrays.

Answer 4

You can write your array to a file, then source the file in your script. e.g.:

array.sh

array=(a b c)

test.sh

source $2
...

Run the test.sh script:

./test.sh argument1 array.sh argument3

Answer 5

If this is your command:

test.sh argument1 ${array[*]} argument2

You can read the array into test.sh like this:

arg1=$1
arg2=${2[*]}
arg3=$3

It will complain at you ("bad substitution"), but will work.