Trying to calculate radius and circle area in BASH

Question

I am trying to write a basic script to calculate the radius and area of ​​a circle, where PI = 3.14, and the circle is given. I am very new to scripting and I cannot figure it out.

#!/bin/bash
PI=3.14
CIRC=5
RAD=echo "((CIRC/2*PI))" | bc-l
printf "Radius: %.2f" $RAD
AREA=echo "((PI*RAD**2))" | bc-l
printf "Area: %.2f" $AREA

The sum of both equations is not stored in these variables, and I have no idea why. Hope someone can help explain.

Answer 1

The below script will do this:

#!/bin/bash
pi=3.14
circ=5
rad=$( echo "scale=2;$circ / (2 * $pi)" | bc )
printf "Radius: %.2f\n" $rad
area=$( echo "scale=2;$pi * $rad * $rad" | bc )
printf "Area: %.2f\n" $area

Notes

• See [command substitution] .
• Never use full uppercase variables in a script, as they are usually reserved for the system, check [this] .
• scale bc , [this].

Answer 2

• bc , printf. $(), . bash echo <<<:

  #!/bin/bash
  PI=3.14
  CIRC=5
  bc <<< "scale=2; r=$CIRC/(2*$PI)
          print "'"Radius: ", r, "\nArea: ", '"$PI"'*(r^2), "\n"'
  

• POSIX, :

  #!/bin/sh
  PI=3.14
  CIRC=5
  bc << snip
        scale=2; r=$CIRC/(2*$PI)
        print "Radius: ", r, "\nArea: ", $PI * (r^2), "\n"
  snip
  

• Pure bc:

  #!/usr/bin/bc -q
  pi=3.14; circ=5; scale=2; r=circ/(2*pi)
  print "Radius: ", r, "\nArea: ", pi*(r^2), "\n"
  quit