Shell script - backup, update and rollback of files

Shell Script —— Backup of files , Update and rollback

Script

#!/bin/bash
read -p " Please enter the absolute path of the directory you want to backup to ：" a
# Both functions and variables are OK here , It can also be done without 
beifen () { 
rsync -arv /mnt/1.txt $a
}

gengxin () {
rsync -auvr -delete  /mnt/1.txt $a
}

huigun () {
rm -rf /mnt/1.txt
cp -rfp $a/1txt /mnt
}

read -p " Please enter the action you want to perform （A: Backup 、B: to update 、C: Roll back ）："  b
case $b in
A)
  beifen
  ;;
B)
  gengxin
  ;;
C)
  huigun 
  ;;
*)
  echo "no"
  exit
esac

perform

END