"Operation not permitted" for command line script, Full Disk Access granted

For what its worth I find it generally best practice to always define the full path to executables in scripts. This has two important benefits.

1. By specifying the full path you ensure you are running a copy of that command in a specific place and prevent the possibility of someone/thing modifying your path to run a dodgy copy in a different location
2. I have found that cron as an example when running a script does not have the same path definition and therefore might not find the executable and hence cause the script to fail even though when you test it by manually running it, it works

If your default shell is zsh, as it is in Catalina, then unless you have a ~/.zprofile exporting your PATH when you launch Terminal and initiate a login zsh shell, or the ~/.zshrc file to set the PATH when you interactively switch between shells — nothing will work right. By changing a shebang to /bin/bash, you are reading Bash specific startup information, and your PATH is getting exported as it did when Bash was the default shell.

This is what I have in my ~/.zprofile and ~/.zshrc files in my home directory:

export PATH=".:$HOME/bin:/usr/local/bin:$PATH"
autoload -U colors && colors
MyHost="$(/usr/sbin/networksetup -getcomputername)"
PS1="%{$fg[blue]%}${MyHost}: %~ %{$reset_color%} %% %{$fg[white]%}"
export EDITOR="/usr/bin/vim"
export HOMEBREW_NO_ANALYTICS=1
export MAXOSX_DEPLOYMENT_TARGET=$(sw_vers -productVersion)

And here is the zsh prompt:

Not all of that content above is necessary.

Not to be insulting, but is the script marked as executable?

Have you tried using the full path to the "ls" utility within the script?

Is the current working directory in the same directory as your script?

What version of macOS? If you are using Catalina, the default shell is now zsh, so $PATH may be different from what you had set with BASH. You can still revert to BASH if you want.

I don't know. Maybe double check the $PATH, your BASH shell settings ("~/.bash_profile", "~/.bashrc", etc. ) and which shell you are actually using:

echo  $PATH
echo  $SHELL

I'm not that familiar with the nuances of the macOS command line which can cause me trouble with the few times I use it since it can behave differently than Linux which I'm familiar with. Maybe another more experienced contributor may know more about the macOS command line behavior.