Editor completion in bash (defaulting to using vi)

get-vi-answer.sh

#!/bin/sh

INSTRUCTIONS="-- This line, and those below, will be ignored. --

Add a business case. The business case should be described briefly in a single
line on the first line, followed by a more detailed description on the
following lines."

CONTENT=""

EDITOR=${EDITOR:-}
VISUAL=${VISUAL:-}
if [[ -z ${VISUAL} && -z ${EDITOR} ]] ; then
	VISUAL=vi
elif [[ -z ${VISUAL} && ! -z ${EDITOR} ]] ; then
	VISUAL=${EDITOR}
fi

until [[ ${CONTENT} =~ [[:alnum:]] ]] ; do

	TMP_CONTENT=$( mktemp )
	echo "" > ${TMP_CONTENT}
	echo "${INSTRUCTIONS}" >> ${TMP_CONTENT}

	${VISUAL} ${TMP_CONTENT}

	CONTENT=$( cat ${TMP_CONTENT} )
	CONTENT="${CONTENT%%${INSTRUCTIONS}}"

	if [[ ! ${CONTENT} =~ [[:alnum:]] ]] ; then
		read -p "No business case entered. Continue or Abort (C/A)? [Abort]: " RESPONSE
		if [[ -z ${RESPONSE} || ! ${RESPONSE} =~ ^[cC] ]] ; then
			exit
		fi
	fi
	rm ${TMP_CONTENT}
done

echo "${CONTENT}"