Check if possible to run command as sudo in Bourne shell? - shell

Question

I'm writing a Bourne shell deployment script, which runs some commands as root and some as the current user. I want to not run all commands as root, and check upfront if the commands I'll need are available to root (to prevent aborted half-done deployments).
In order to do this, I want to make a function that checks if a command can be run as root. My idea was to do this:
sudo_command() {
sudo sh -c 'type "$1"'
}
And then to use it like so:
required_sudo_commands="cp rm apt"
for command in $required_sudo_commands do
sudo_command "$command" || (
echo "missing required command: $command;
exit 1;
)
done
As you might guess by my question here: it doesn't work. Does any of you see what I'm doing wrong here?
I tried running the command inside sudo_command by itself, but that miraculously (to me) did work. But when I put the command into a separate file, it didn't work.

Answer 1

There are two immediate problems:
The $1 not expanding in single quotes.
You can semi-fix this by expanding it in double quotes instead: sudo sh -c "type '$1'"
Your command not exiting. That's easily fixed by replacing your || (..) with || {..}.
(..) creates a subshell that limits the scope of everything inside it including exit. To group commands, use {..}
However, there is also the fundamental problem of trying to use sh -c 'type "$1" to do anything.
One of the major points of sudo is the ability to limit what a user can and can't do. You're assuming that a user has complete, unrestricted access to run arbitrary commands as root, and that any problems are due to root not having these commands available.
That may be a valid assumption for you, but you may want to instead run e.g. sudo apt --version to get a better (but still incomplete) picture of whether you're allowed and able to run apt with sudo without requiring complete and unrestricted access.