Bash error “command not found” running a command stored in var

Context:

I want to run a command stored in a variable in bash.

My bash file:

#!/bin/bash
# -----------------------------------------------
# ---                COMMANDS                 ---
# ---              Vanilla style              ---
# -----------------------------------------------
GRUNT="node_modules/grunt-cli/bin/grunt"
LS="ls"
# -----------------------------------------------
# ---                COMMANDS                 ---
# ---              Using Docker               ---
# -----------------------------------------------
GRUNT="docker exec compose_custom-node_1 node_modules/grunt-cli/bin/grunt"
LS="docker exec compose_custom-node_1 ls"


# ***********************************************
# ***                Execution                ***
# ***********************************************
# -----------------------------------------------
# Compile SCSS using Grunt
# -----------------------------------------------
echo "Building CSS from Sass files..."
echo "$(docker exec compose_custom-node_1 ls -l)"
echo "$($LS -l)"
$($GRUNT sass)

Problem:

When I run this bash file, the grunt sass command throws an error:

mybash.sh: line 25: $'E[4mRunning' : command not found

Whole return of my bash:

darckcrystale@kermit:/var/www/my_folder$ ./my_bash.sh
Building CSS from Sass files...
total 188
-rw-rw-r--   1 node node  3627 May  2 19:00 Gruntfile.js
drwxr-xr-x 282 root root 12288 May  3 12:12 node_modules
drwxr-xr-x   4 node node  4096 May  2 18:39 sass
total 188
-rw-rw-r--   1 node node  3627 May  2 19:00 Gruntfile.js
drwxr-xr-x 282 root root 12288 May  3 12:12 node_modules
drwxr-xr-x   4 node node  4096 May  2 18:39 sass
my_bash.sh: ligne 25: $'E[4mRunning' : commande introuvable

Investigation:

The commands echo "$(docker exec compose_custom-node_1 ls -l)" and echo "$($LS -l)" seem to work, but not the $($GRUNT sass).

If I run docker exec compose_custom-node_1 node_modules/grunt-cli/bin/grunt in a terminal, I see this output:

Running "sass:app1" (sass) task
Running "sass:sticky-app2" (sass) task
Done, without errors.

Question:

Do you have a clue for me? What I am doing wrong?

Answer

Better to use a function to store complex commands than a variable,

grunt() {
    docker exec compose_custom-node_1 node_modules/grunt-cli/bin/grunt "$@"
}

and call this as just

grunt "saas"

wherever needed in your script. See BashFAQ-050 which talks about this exact requirement on complex cases.