如何理解linux关系运算符

if [ $x == 5 ]; then
  echo "x is equal to 5"
fi

if [ $x != 5 ]; then
  echo "x is not equal to 5"
fi

if [ $x > 5 ]; then
  echo "x is greater than 5"
fi

if [ $x < 5 ]; then
  echo "x is less than 5"
fi

if [ $x >= 5 ]; then
  echo "x is greater than or equal to 5"
fi

if [ $x <= 5 ]; then
  echo "x is less than or equal to 5"
fi