name="John"
echo "${name}"
echo "${name/J/j}"    #=> "john" (substitution)
echo "${name:0:2}"    #=> "Jo" (slicing)
echo "${name::2}"     #=> "Jo" (slicing)
echo "${name::-1}"    #=> "Joh" (slicing)
echo "${name:(-1)}"   #=> "n" (slicing from right)
echo "${name:(-2):1}" #=> "h" (slicing from right)
echo "${food:-Cake}"  #=> $food or "Cake"

str="Hello world"
echo "${str:6:5}"    # "world"
echo "${str: -5:5}"  # "world"

length=2
echo "${name:0:length}"  #=> "Jo"

${foo:(-3):3}

${foo:0:3}

length=7
echo "${variable:0:length}" # => Some st
# This will return only the first 7 characters of the value
echo "${variable: -5}" # => tring
# This will return the last 5 characters (note the space before -5).
# The space before minus is mandatory here.