getyn

#!/bin/bash
#
# getyn
#
# getyn() $1
#
# Takes $1 for a prompt string
# Places true or false command into $2, which is an optional argument.
# User is prompted for (y/n) answer at the end of the prompt string.
#

usagestr=$(
cat <<EOF

$(basename $0) prompt

Given a prompt string, user is prompted for a y/n answer. Only y or n are
accepted as valid responses, so the prompt is presented in a loop until
the user types either y or n.

Returns 0 if response was y
Returns 1 if response was n

Note:
	You cannot use this script if there is a pending read. For example,
	the following will not function properly, because "\$lines" string
	is being read by the while loop, so the read in getyn encounters
	a buffer of pending characters.

	while IFS= read line; do
		getyn "Show this line?"
		[ $? -eq 0 ] && echo "\$line"
	done <<< "\$lines"
\0
EOF
)

usage() {
	echo -e "$usagestr"
	exit
}

[ "$1" == "-h" ] && usage
[ $# -gt 0 -a $# -le 1 ] || usage

declare promptstring="$1"
declare answer

while true; do

	echo -en "$promptstring (y/n) : "
	read -n1 answer
	echo

	[ "$answer" == "y" ] && exit 0
	[ "$answer" == "n" ] && exit 1

	echo "Please answer y or n."
done