checkcommand() {
#controllo del comando (da fare)
}

checkfile() {
STRING=${1}
FILE=${2}
	if [ ! -f ${FILE} ]
	then 
		echo "${FILE} does not exist"
		EXIST="nofile"
		return 1
	else
		info=`cat ${FILE} | grep "${STRING}"`
		if [ "$info" != "" ]
		then
			EXIST="yes"
		else
			EXIST="no"
		fi
	fi
}

write() {
STRING=${1}
FILE=${2}
	function checkfile ${STRING} ${FILE}
	if [ "$EXIST" = "yes" ]
	then
		echo "Error: \"${STRING}\" already wrote in \"${FILE}\""
		return 1
	else
		echo ${STRING} >> ${FILE}
		echo "\"${STRING}\" wrote in \"${FILE}\""
	fi
}

delete() {
STRING=${1}
FILE=${2}
	function checkfile ${STRING} ${FILE}
	if [ "$EXIST" = "no" ]
	then
		echo "Error: \"${STRING}\" not wrote in \"${FILE}\""
		return 1
	else
		touch ${FILE}.delete
		cat ${FILE} | grep -v ${STRING} > ${FILE}.delete
		mv ${FILE}.delete ${FILE}
		echo "\"${STRING}\" deleted from \"${FILE}\""
	fi
}