alt-bc.sh

Shall高级编程

#!/bin/bash
# Invoking 'bc' using command substitution
# in combination with a 'here document'.


var1=`bc << EOF
18.33 * 19.78
EOF
`
echo $var1       # 362.56


#  $( ... ) notation also works.
v1=23.53
v2=17.881
v3=83.501
v4=171.63

var2=$(bc << EOF
scale = 4
a = ( $v1 + $v2 )
b = ( $v3 * $v4 )
a * b + 15.35
EOF
)
echo $var2       # 593487.8452


var3=$(bc -l << EOF
scale = 9
s ( 1.7 )
EOF
)
# Returns the sine of 1.7 radians.
# The "-l" option calls the 'bc' math library.
echo $var3       # .991664810


# Now, try it in a function...
hypotenuse ()    # Calculate hypotenuse of a right triangle.
{                # c = sqrt( a^2 + b^2 )
hyp=$(bc -l << EOF
scale = 9
sqrt ( $1 * $1 + $2 * $2 )
EOF
)
# Can't directly return floating point values from a Bash function.
# But, can echo-and-capture:
echo "$hyp"
}

hyp=$(hypotenuse 3.68 7.31)
echo "hypotenuse = $hyp"    # 8.184039344


exit 0