How to access shell variable value from Node.js?

Question

Let's say there is a variable key1 and its value is 123

key1=123

so when I run the command in linux environment echo $key1, I get output as 123.

Now I have the following gulp task.

const child_process = require('child_process');
....
gulp.task('printKeyValue', function() {
    var value1 = child_process.execSync('echo $key1');
    console.log(value1.toString().trim());
});

Here, I'm trying to access value of linux variable from nodejs by using Child Process

But when I run the following gulp task, I don't get the desired output.

npm run gulp -- printKeyValue

Instead I get output as $key1 and not 123.

See below screenshot

Other commands like ls & pwd in gulp task gives the desired output.

Can some one please help on this or suggest an alternate way?

Actually not sure if duplicate. Do you want to access an environment variable in Node.js like your title says, or in a subprocess command line like your code says? — Amadan
– Amadan, Commented Oct 16, 2018 at 11:41
@Amadan Thank you for redirecting me to an alternate solution. After looking the solution, I tried console.log(process.env.key1); I get the output as undefined which is not the expected output. — Siddarth
– Siddarth, Commented Oct 16, 2018 at 11:46
Can't read my environment variable in my Node.js app, Read environment variables in Node.js — jww
– jww, Commented Oct 17, 2018 at 7:47
Possible duplicate of Can't read my environment variable in my Node.js app — Makyen
– Makyen ♦, Commented Oct 18, 2018 at 0:07

Community · Accepted Answer · 2020-06-20 09:12:55Z

You are not exporting the variable. When you just do

key1=123

the variable is not propagated to subprocesses. It will be available in your current bash process, so you can see it when you type echo $key1, but it will not get inherited by the node process. As man bash says:

When a simple command other than a builtin or shell function is to be executed, it is invoked in a separate execution environment that consists of the following. Unless otherwise noted, the values are inherited from the shell.

[...]

shell variables and functions marked for export, along with variables exported for the command, passed in the environment

You need to either define the variable as exported

export key1=123

or mark an existing variable for export

key1=123
export key1

or launch your node with the modified environment, either via the bash innate capability to do so

key1=123 node code.js

or using /usr/bin/env utility:

env key1=123 node code.js

Once the variable is properly passed to the node process, it will be available both in process.env.key1 and as $key1 in a child process.

EDIT: I just noticed, you actually gave the command you're running; it does not matter, the same logic goes for every executable, whether node or npm or anything else.

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