How to pass environment variable if it is an array

[ddimitrioglo]

---

• Version: v6.11.4
• Platform: Darwin Kernel Version 17.2.0: Fri Sep 29 18:27:05 PDT 2017; root:xnu-4570.20.62~3/RELEASE_X86_64 x86_64

---

Let's assume that we have test.sh with content:

for item in "${list_variable[@]}"; do echo ${item}; done

and we have test.js

'use strict';

const { exec } = require('child_process');

let env = {
  list_variable: ['one', 'two', 'three']
};

exec('bash test.sh', { env }, (error, stdout) => {
  console.log(stdout);
});

I expect to see

one
two
three

but receiving: one,two,three

Please help me understand the root cause..

P.S. Guys from https://github.com/nodejs/node redirected me here.

[ORESoftware]

Surprised nobody responded yet, sorry you had to wait for an answer.

What you want to do:

let env = {
  list_variable: JSON.stringify(['one', 'two', 'three']);
};

then parse that in the child process. Or you can do this:

let env = {
  list_variable: ['one', 'two', 'three'].join(',')  // a comma separated string
};

and use this:
https://stackoverflow.com/questions/27702452/loop-through-a-comma-separated-shell-variable

list_variable=one,two,three
for i in ${variable//,/ }
do
    # call your procedure/other scripts here below
    echo "$i"
done

[ddimitrioglo]

Thank you, @ORESoftware!
This is cool workaround if you have control in your bash script, but in my case I don't, I'm wondering if its possible to pass an array, not to transform coma-separated string into array.

Generally it looks like node transforms any data into string...

[ORESoftware]

Here's an answer:
https://stackoverflow.com/questions/47936076/log-every-item-in-json-array-in-newline/47936487#47936487

[ORESoftware]

Yeah, bash might have some string format for arrays, not sure. But it's easy to create a comma separated, or newline separated, string with node.js, and write that string to the env variable.

[ddimitrioglo]

That's the salt...
I do not have access to the bash, and it needs that env variable to be an array.

[ORESoftware]

yeah dunno :) I am not sure if you can construct a bash array with just a string format

http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_10_02.html

[bnoordhuis]

Generally it looks like node transforms any data into string...

That's because environment variables are strings. You can't make it work for the same reason why env list_variable="..." bash test.sh won't work.

I guess you could do something like this:

const s = 'list_variable=(one two three)\n' + fs.readFileSync('test.sh', 'utf8');
child_process.spawn('bash', ['-c', s]);

[ORESoftware]

I asked this question just now - in general unix.stackexchange.com is your friend - nicer people on their than stackoverflow :)

https://unix.stackexchange.com/questions/412454/construct-bash-array-with-only-string-format

[ORESoftware]

@ddimitrioglo I think @bnoordhuis is onto something

[gireeshpunathil]

looks like this is answered and resolved, @ddimitrioglo please let me know if that is not the case.

[ddimitrioglo]

In this particular use-case - it's ok, but it still a workaround, and we will face the issue again by running not a bash file but an binary (for example terrraform plan command (https://www.terraform.io/docs/commands/plan.html), where I can pass vars like TF_ prefixed environment variables)

[gireeshpunathil]

@ddimitrioglo - As I understand, this is not a node.js programming issue, rather a fundamental limitation on passing user defined types such as arrays into child processes, right? in other words, there is no evidence that this is feasible in any other language / framework etc. (The bash documentation refers this as a limitation)

I would suggest usage of arrays intrinsic to the program where they are created and used. In other scenarios, consider delimited environment variables (if the values are discrete) or configuration files if the list is big, and modify the consuming code accordingly. [ I read as you mentioning the consuming code cannot be modified, but I don;t see any other solution for this]

Hope this explanation helps.

[gireeshpunathil]

closing as answered.