convert to lowerercase in shell script code example

Example 1: convert all files to lowercase using shell script

#!/bin/sh

for x in `ls`
  do
  if [ ! -f $x ]; then
    continue
    fi
  lc=`echo $x  | tr '[A-Z]' '[a-z]'`
  if [ $lc != $x ]; then
    mv -i $x $lc
  fi
  done

Example 2: convert capital letters to lowercase in shell script

x="HELLO"
echo $x  # HELLO

y=${x,,}
echo $y  # hello

z=${y^^}
echo $z  # HELLO