shell算术运算 – 运维生存时间

A+

所属分类：Linux

1、bc计算

bc_test=`echo “10 + 1″ | bc`
file_size=`echo “${data_size[“${i}”]} + ${index_size[“${i}”]}” | bc`

1 2	bc_test=`echo “10 + 1″ \| bc` file_size=`echo “${data_size[“${i}”]} + ${index_size[“${i}”]}” \| bc`

根据不同系统可能遇到如下错误

 (standard_in) 1: illegal character: N
(standard_in) 1: illegal character: U
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: L
(standard_in) 1: syntax error
(standard_in) 1: illegal character: N
(standard_in) 1: illegal character: U
(standard_in) 1: illegal character: L
(standard_in) 1: illegal character: L

(standard_in) 1: illegal character: N

(standard_in) 1: illegal character: U

(standard_in) 1: illegal character: L

(standard_in) 1: syntax error

(standard_in) 1: illegal character: N

(standard_in) 1: illegal character: U

(standard_in) 1: illegal character: L

2、expr计算

expr_text=`expr 1 + 1`
file_size=`expr ${data_size[“${i}”]} + ${index_size[“${i}”]}`

1 2	expr_text=`expr 1 + 1` file_size=`expr ${data_size[“${i}”]} + ${index_size[“${i}”]}`

可能遇到错误如下

 expr: non-integer argument

1	expr: non-integer argument

3、$(( ))计算

file_size=$((${data_size[“${i}”]} + ${index_size[“${i}”]}))

1	file_size=$((${data_size[“${i}”]} + ${index_size[“${i}”]}))

并且可以进行进制转换
十六进制转十进制：

 [root@localhost ~]$ ((num=0xff));
[root@localhost ~]$ echo $num;
255
[root@localhost ~]$ ((num=16#ff));
[root@localhost ~]$ echo $num;
255

[root@localhost ~]$ ((num=0xff));