Check to see if a command exists at #shell
If you want to check to see if a command exists on a user's machine you can use command -v. command without flags will run the command passed as an argument.
> command echo "A"
"A"
command -v with the -v flag will return the path of the command, and most importantly, a non-zero status code if that command does not exist.
> command -v brew
/usr/local/bin/brew
Or on Linux
> command -v brew
# returns nothing and also returns a status code of 1
Importantly, you can check for a command before using it.
command -v brew && brew install something