Shell Script: upper case to lower case or vice versa

• Uppercase to lowercase:
  
  

  echo $VAR | tr '[:upper:]' '[:lower:]'
  

  
  or
  
  

  echo $VAR | tr '[A-Z]' '[a-z]'
  

  
  
• Lowercase to uppercase:
  
  

  echo $VAR | tr '[:lower:]' '[:upper:]'
  

  
  or
  
  

  echo $VAR | tr '[a-z]' '[A-Z]'