查看“Shell中的浮点数运算”的源代码

** with awk:

# x=3.1; y=3.2; echo "$x $y" | awk '{if ($1 > $2) print $1; else print $2}'
3.2 echo 3.14 + 5.16 | bc

** with bc:
#!/bin/bash
echo "Enter value1"
read value1
echo "Enter value2"
read value2

Result=`echo "$Value1 > $Value2" | bc `

if [ $Result -eq 1 ]
then
echo "$value1 is greater"
fi

> echo 3.14 + 5.16 | bc
8.30


** Bash does not understand floating point arithmetic.  It treats numbers containing a decimal point as strings. Some shells like zsh understand floating point. Here's a sample comparing bash and zsh. It writes a file t1, then asks bash and zsh to execute it:
Code:

#!/bin/sh
# @(#) s1 Compare bash and zsh for arithmetic.

set -o nounset

cat >t1 <<'EOF'

if [ -n "$BASH_VERSION" ]
then
echo " From bash, version :$BASH_VERSION:"
elif [ -n "$ZSH_VERSION" ]
then
echo " From zsh, version :$ZSH_VERSION:"
else
echo " Unknown shell."
fi

float X Y
(( X = 3.0 + 0.5 ))
(( Y = 33.0 / 10.0 ))
if (( $X < $Y )) # is $X less than $Y ?
then
echo "\$X=${X}, which is less than \$Y=${Y}"
elif (( $X > $Y ))
then
echo "\$X=${X}, which is greater than \$Y=${Y}"
fi

EOF

echo
bash t1

echo
zsh t1

exit 0

Producing:
Code:

% ./s1

From bash, version :2.05b.0(1)-release:
t1: line 12: float: command not found
t1: line 13: ((: X = 3.0 + 0.5 : syntax error in expression (error token is ".0+ 0.5 ")
t1: line 14: ((: Y = 33.0 / 10.0 : syntax error in expression (error token is ".0 / 10.0 ")
$X=3, which is less than $Y=33

From zsh, version :4.2.4:
$X=3.500000000e+00, which is greater than $Y=3.300000000e+00


** Here is another example change float to integer
Code:

a=2.25
b=1.35

function f_dec2int()
{
n=$1
if [ "`echo $n | grep '.'`" != "" ]
then
echo $n | sed 's/\.//'
fi
}


if [ `f_dec2int $a` -lt `f_dec2int $b` ]
then
echo true
else
echo false
fi

## `f_dec2int $a` \\ 225
## `f_dec2int $b` \\ 135