# check if two directories are on the same device:
 if [[ $(stat -c%d /) != $(stat -c%d $DIR_NAME) ]] ; then
  echo "Directories are NOT on the same device"
 else
  echo "Directories are on the same device"
 fi


# remove chars from a string
var=../dir ; echo ${var//i/} 
../dr
var=../dir ; echo ${var//./} 
/dir


# replace chars in a string
var=../dir ; echo ${var//i/a}
../dar


# skip leading characters
var=../dir ; echo ${var:3}   
dir