Operations in shell

1. Operation symbol

+	Add
-	Subtraction
*	Multiplication
/	division
%	The remainder of the division      8%10=8
**	chengfang                     echo $[2**3]=8
++	Self plus one
--	Self subtraction one
<	Less than
<=	Less than equal and
>	Greater than
>=	Greater than equal to
>=	be equal to
+=	((i=1;i<=10;i++))   ((n+=i)) Add up   echo $n
*=	j=j*i
/=	j=j/i
%=	j=j%i

2. Operation instruction

①(())        ((a=2+3))      echo $a

②let         let a=2+3      echo $a

③expr      expr 1 + 2

④echo $[1+2]

⑤bc << EOF

1+3

EOF

Calculate retained decimal

printf '%0.2f' .3 ==== 0.30      Keep two decimal places

printf '%0.3f' .3 ====0.300      Keep three decimal places

printf '%0.4f' .3 ====0.3000    Keep four decimal places

awk  ‘{n=$1+$2;print n}’ file                     file Add the first number and the second number in the file

echo 2 3 | awk  ‘{n=$1+$2;print n}’          awk Calculate the whole number 2+3

echo 0.2 0.3 | awk  ‘{n=$1+$2;print n}’    awk Calculate decimal addition