Prompt to continue if no argument passed - bash

Question

I want to prompt to do something or not. And if a specific argument such as "-y" or "--yes" is passed I want to make the script non-interactive (force user answer).
if [ $# = 1 ] && [ "$1" = "-y" ]; then
# my code here
else
read -n 1 -p "¿Install this? [y/N] "
if [[ $REPLY =~ ^([Yy])$ ]]; then
# same code here
fi
fi
If I had to use a function I would like it to be something not to do with the code but with the test as I have a lot of this tests in the script.
function(argument)
{
if [ $# = 1 ] && [ "$1" = "-y" ]; then
return true
else
read -n 1 -p "$argument [y/N] "
if [[ $REPLY =~ ^([Yy])$ ]]; then
return true
fi
fi
}
if function("¿Install this?"); then
# my code here
fi
This function is wrong because it overrides the script's argument with the function call's argument.
install_maybe () {
echo $# $1
if [ $# = 1 ] && [ "$1" = "-y" ]; then
return 0
else
read -n 1 -p "$1 [y/N] "
if [[ $REPLY =~ ^[Yy]$ ]]; then
return 0
fi
fi
return 1
}
if install_maybe "Install everything?"; then
source "$DOTFILES/install/esential" "-y"
else source "$DOTFILES/install/esential"
fi

Answer 1

Simply define a flag in a variable that indicates the presence / absence of -y, the auto-confirmation option, among the command-line arguments, and pass that flag to your helper function as a 2nd argument:
#!/bin/bash
# Helper function to ensure that the user has confirmed the intent to proceed.
assertConfirmation() {
local promptMsg=$1 autoConfirm=$2
if (( autoConfirm )); then
return
else
read -n 1 -p "$promptMsg [y/N] "
printf '\n' # Output a newline, because none was appended to the user's keypress.
if [[ $REPLY =~ ^([Yy])$ ]]; then
return
fi
fi
# Getting here means: confirmation was not given - abort the script as a whole.
echo "Aborted." >&2 # Note how the message is sent to *stderr*.
exit 2 # Use a dedicated exit code to signal this condition.
}
# ... Code that performs proper parsing of command-line arguments,
# such as with getopts or GNU getopt, omitted for brevity.
# Here, I assume that the option to signal automatic confirmation
# is in $1, if provided.
[[ $1 == '-y' ]] && autoConfirm=1 || autoConfirm=0
# Call the helper function, which only returns if confirmation is
# either implied by the relevant command-line option or, in its absence,
# by the user confirming the intent to proceed interactively.
assertConfirmation "Install everything?" "$autoConfirm"
# Proceed...
echo "Installing..."