How can I get bash to evaluate a PM2 command stored in a Variable?

I'm setting up a server config with cloud init and am running commands one after another in the config file.

One of the commands I need to run to setup my server's environment is PM2 to keep a node server app online after reboot. I am able to have PM2 output a special command I need to run and am storing that command in a variable to run in the next line.

Command 1: (Storing the Output)

pm2response=$(pm2 startup systemd)

Command 2: (Executing the response command and trimming extra logging)

${pm2response#*Execute the following command:}

When I run Command 2 in my playground server, it outputs the error

[PM2][ERROR] Init system not found

I don't understand why I can't store the command output in a variable and execute the variable. I have manually copied the exact command I need to run into the console and successfully executed it. It's just storing it in a variable that doesn't work.

Command I need to execute as a variable: (This works successfully)

sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username

Command I tried executing as a variable: (Has errors)

var='sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username'
$var

Why won't this work?

Update

I got the $var to work using double quotes in my server.

var="sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username"
$var #works!

Although this is just an example I was testing in a playground server. For clarity of the question, I'm really trying to evaluate Command 2:

${pm2response#*Execute the following command:}

Reference for Command 2: I'm using the shell parameter substitution so I can remove logging. This is the output without the shell parameter substitution.

echo $pm2response: (will output)

[PM2] Init System found: systemd [PM2] You have to run this command as root. Execute the following command: sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username

So by adding shell parameter substitution,
echo ${pm2response#*Execute the following command:}: (will output)

sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username

1 Answer

Try either of these lines:

var="sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username"
$var
var1=$("sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username")
$var1

The error on the one you used happens because expressions don't expand in single quotes, use double quotes for that:

var='sudo env PATH=$PATH:/usr/bin /usr/lib/node_modules/pm2/bin/pm2 startup systemd -u username --hp /home/username'
$var