shell算术运算

1、bc计算

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

2、expr计算

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

可能遇到错误如下文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/

 expr: non-integer argument

3、$(( ))计算

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：文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/

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

base-32转十进制：文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/

 [root@localhost ~]$ ((num=32#ffff));
[root@localhost ~]$ echo $num;
507375

base64转十进制：文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/

 [root@localhost ~]$ ((num=64#abc_));
[root@localhost ~]$ echo $num;
2667327

二进制转十进制文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/

 [root@localhost ~]$ ((num=2#11111111));
[root@localhost ~]$ echo $num;
255

十进制转八进制
这里使用到：bc外部命令完成。bc命令格式转换为：echo “obase=进制;值”|bc文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/

 [root@localhost ~]$ echo “obase=8;01234567″|bc
4553207

二进制，十六进制，base64转换为 十进制也相同方法。文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/

 [root@localhost ~]$ echo “obase=64;123456″|bc
30 09 00

 文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/ 文章源自运维生存时间-https://www.ttlsa.com/linux/shell-calc/