How do I always answer No to any prompt with a bash script?

actually, it looks funny ...

$ yes no

manpages excerpt:

$ man yes 

YES(1)                    BSD General Commands Manual                   YES(1)

NAME
     yes -- be repetitively affirmative

SYNOPSIS
     yes [expletive]

DESCRIPTION
     yes outputs expletive, or, by default, ``y'', forever.

...

yes no | <command>

Where <command> is the command you want to answer no to.

(or yes n if you actually need to just output an n)

The yes command, by default, outputs a continuous stream of y, in order to answer yes to every prompt. But you can pass in any other string as the argument, in order for it to repeat that to every prompt.

As pointed out by "just somebody", yes isn't actually standardized. While it's available on every system I've ever used (various BSDs, Mac OS X, Linux, Solaris, Cygwin), if you somehow manage to find one in which it doesn't, the following should work:

while true; do echo no; done | <command>

Or as a full-fledged shell script implementation of yes, you can use the following:

#!/bin/sh

if [ $# -ge 1 ]
then
    while true; do echo "$1"; done
else
    while true; do echo y; done
fi

for systems with no such command, just a simple echo should work

echo "no" | command

for repetitions , not that hard to make a while/for loop that goes on forever.