Why my Bash script ran in yarn/npm is throwing errors?

I’ve encountered this error a few times in different projects. Unfortunately I usually tend to forget why this is happening, because it’s not such frequent error. Now I decided to write it down, at least as a note for myself. Hopefully it helps someone else too!

Without further ado, when running a script via yarn, I get something like this:

./scripts/my-script.sh: 24: [[: not found

But when running in my terminal, the error does not occur. Pretty peculiar indeed. This is usually due to yarn script defined as "domagic": "sh ./scripts/my-script.sh". What that does is, it is forcing the script to be run with sh interpreter. Since I’m using Linux Mint, this means it will be ran in Dash (Debian Almquist Shell) instead of Bash, even though the script file has a shebang #!/bin/bash. So what is Dash and why it is set as a default shell in Linux Mint? Here’s a writing in ubuntu wiki which also applies to Linux Mint, because it uses ubuntu as a base.

How can I see what shell my Linux distro is using? It’s rather easy with readlink and which. readlink is used to read symbolic links and which locates a command, thus by running readlink $(which sh) you’ll get the interpreter used for sh. For me it outputs dash.