shell的浮点运算

Quote:

Originally Posted by mkrems

I have a bash script with the following line where $timestep is a decimal number.

t=$timestep*$i

echo $t gives the value "0.125*2" for example instead of "0.250".
How do I change this?!?

bash does not have floating point arithmetic. Any variable with a decimal point in it is treated as a string. So bash processes t=$timestep*$i as the concatenation of three strings. The strings are:
$timestep=0.125
*
$i=2

You are not going to get bash to use 0.125 as a number in an arithmetic expression.

--------------------
Steve Stites

colucix · 02-04-2008, 06:33 PM

To do floating point calculations in a shell script you can invoke awk, e.g.

Code:

timestep=0.125
i=2
t=$(echo $timestep $i | awk '{printf "%4.3f
",$1*$2}'

or you can use bc calculations (see man bc for details).

02-04-2008, 06:33 PM	#4
colucix LQ Guru Registered: Sep 2003 Location: Bologna Distribution: CentOS 6.5 OpenSuSE 12.3 Posts: 10,509 Rep:	To do floating point calculations in a shell script you can invoke awk, e.g. Code: timestep=0.125 i=2 t=$(echo $timestep $i \| awk '{printf "%4.3f ",$1*$2}' or you can use bc calculations (see man bc for details).