"invalid arithmetic operator" error when trying to add variables in Bash script

Question

Coming from a Python background, this is my first simple Bash script and it does not work. I'm confused.

#!/bin/bash
RTCHOST='192.168.0.143'
PANEL1=$(client read-value --host $RTCHOST --name dc_1)
echo Panel1: $PANEL1
PANEL2=$(client read-value --host $RTCHOST --name dc_2)
echo Panel2: $PANEL2
PANELCONSUMPTION=$(($PANEL1 + $PANEL2))
echo Consumption: $PANELCONSUMPTION

When I run the script, I get a syntax error:

invalid arithmetic operator

怎么了？

Answer 1

我猜$PANEL1和$PANEL2是浮点数。但是，Bash 只能处理整数，不能处理浮点数，如算术扩展中所述。如果您尝试对浮点数求和，则会出现错误invalid arithmetic operator。

只需在这里尝试一下：

#!/bin/bash
A='5'
B='6.4'
C=$(($A + $B))
echo $C

Stack Overflow 线程中描述了添加浮点数：How can I add numeric in a Bash script?

本质上，您可以使用外部实用程序（例如 ）bc来执行此示例中所示的操作：

#!/bin/bash
A='5'
B='6.4'
C=$(echo $A + $B | bc) 
echo $C

这有效并返回预期值 11.4。