if statement linux bash code example

Example 1: bash if statement

and - &&
or - ||

# and example
if [ -r $1 ] && [ -s $1 ]
then
echo This file is useful.
fi

# or example
if [ $USER == 'bob' ] || [ $USER == 'andy' ]
then
ls -alh
else
ls
fi

Example 2: bash if else if

if [[ TEST-COMMAND ]]
then
  STATEMENTS1
else
  STATEMENTS2
fi