How to do integer & float calculations, in bash or other languages/frameworks?

Question

Using echo "20+5" literally produces 20+5

What command can I use to get the actual sum, e.g. 25 in this case.

Also, what's the easiest way to do it just using bash for floating point, e.g.
echo $((3224/3807.0)) gives 0 :(

Using either the basic command shell ('command line') itself or through using languages that are available at the command line.

Answer 1

There are lots of options!!!

Summary

$ echo $((20.0/7))
$ zcalc
$ bc <<< 20+5/2
$ bc <<< 'scale=4;20+5/2'
$ expr 20 + 5
$ calc 2 + 4
$ node -pe 20+5/2  # Uses the power of JavaScript, e.g. : node -pe 20+5/Math.PI
$ echo 20 5 2 / + p | dc 
$ echo 4 k 20 5 2 / + p | dc 
$ perl -E "say 20+5/2"
$ python -c "print 20+5/2"
$ python -c "print 20+5/2.0"
$ clisp -x "(+ 2 2)"
$ lua -e "print(20+5/2)"
$ php -r 'echo 20+5/2;'
$ ruby -e 'p 20+5/2'
$ ruby -e 'p 20+5/2.0'
$ guile -c '(display (+ 20 (/ 5 2)))'
$ guile -c '(display (+ 20 (/ 5 2.0)))'
$ slsh -e 'printf("%f",20+5/2)'
$ slsh -e 'printf("%f",20+5/2.0)'
$ tclsh <<< 'puts [expr 20+5/2]'
$ tclsh <<< 'puts [expr 20+5/2.0]'
$ sqlite3 <<< 'select 20+5/2;'
$ sqlite3 <<< 'select 20+5/2.0;'
$ echo 'select 1 + 1;' | sqlite3 
$ psql -tAc 'select 1+1
$ R -q -e 'print(sd(rnorm(1000)))'
$ r -e 'cat(pi^2, "\n")'
$ r -e 'print(sum(1:100))'
$ smjs
$ jspl

Details

You can use POSIX arithmetic expansion echo $((...)):

$ echo $((20+5))
25
$ echo $((20+5/2))
22

---

ksh93 and zsh do support floats there:

$ echo $((4*atan(1)))
3.14159265358979324

(in zsh, you need zmodload zsh/mathfunc to get the math functions like atan above).

---

Interactively with zsh:

$ autoload zcalc
$ zcalc
1> PI/2
1.5708
2> cos($1)
6.12323e-17
3> :sci 12
6.12323399574e-17

---

Witch (t)csh:

% @ a=25 / 3; echo $a
8

---

In the rc shell family, akanga is the one with arithmetic expansion:

; echo $:25/3
8

---

Or bc (see below for interactive mode): Mnemonic: B est C alculator

$ bc <<< 20+5/2
22
$ bc <<< 'scale=4;20+5/2'
22.5000

---

bc interactive mode:

$ bc
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'. 
5+5
10

2.2+3.3
5.5

---

Or Rush's solution, expr (no interactive mode):

$ expr 20 + 5
25
$ expr 20 + 5 / 2
22

---

or DQdims's calc (required sudo apt-get install apcalc):

$ calc 2 + 4
6

---

Or manatwork's solution, node (interactive mode: node; output function not needed):

$ node -pe 20+5/2  # Uses the power of JavaScript, e.g. : node -pe 20+5/Math.PI
22.5

---

Or Arcege's solution, dc (interactive mode: dc):

Which is even more fun since it works by reverse polish notation.

$ echo 20 5 2 / + p | dc 
22
$ echo 4 k 20 5 2 / + p | dc 
22.5000

But not as practical unless you work with reverse polish notation a lot.

---

Or Perl (interactive mode: perl -de 1):

$ perl -E "say 20+5/2"
22.5

---

Or Python (interactive mode: python; output function not needed):

$ python -c "print 20+5/2"
22
$ python -c "print 20+5/2.0"
22.5

---

Or if you have clisp installed, you can also use polish notation:

$ clisp -x "(+ 2 2)"

---

Or Marco's solution, lua (interactive mode: lua):

$ lua -e "print(20+5/2)"
22.5

---

PHP (interactive mode: php -a):

$ php -r 'echo 20+5/2;'
22.5

---

Ruby (interactive mode: irb; output function not needed):

$ ruby -e 'p 20+5/2'
22
$ ruby -e 'p 20+5/2.0'
22.5

---

Guile (interactive mode: guile):

$ guile -c '(display (+ 20 (/ 5 2)))'
45/2
$ guile -c '(display (+ 20 (/ 5 2.0)))'
22.5

---

S-Lang (interactive mode: slsh; output function not needed, just a ; terminator):

$ slsh -e 'printf("%f",20+5/2)'
22.000000
$ slsh -e 'printf("%f",20+5/2.0)'
22.500000

---

Tcl (interactive mode: tclsh; output function not needed, but expr is):

$ tclsh <<< 'puts [expr 20+5/2]'
22
$ tclsh <<< 'puts [expr 20+5/2.0]'
22.5

---

SQLite (interactive mode: sqlite3):

$ sqlite3 <<< 'select 20+5/2;'
22
$ sqlite3 <<< 'select 20+5/2.0;'
22.5

---

Various SQL's:
SQLite:

echo 'select 1 + 1;' | sqlite3 

MySQL:

mysql -BNe 'select 1+1'

PostgreSQL:

psql -tAc 'select 1+1

_The options on mysql and postgres stop the 'ascii art' image !

---

R in plain mode - lets generate 1000 Normal random numbers and get the standard deviation and print it

$ R -q -e 'print(sd(rnorm(1000)))'
> print(sd(rnorm(1000)))
[1] 1.031997

---

R using the littler script - lets print pi squared

$ r -e 'cat(pi^2, "\n")'
9.869604
$  r -e 'print(sum(1:100))'
[1] 5050

---

PARI/GP, an extensive computer algebra system for number theory, linear algebra, and many other things

$ echo "prime(1000)"|gp -q
7919                        // the 1000th prime
$ echo "factor(1000)" | gp -q
[2 3]
[5 3]                       // 2^3*5^3
$ echo "sum(x=1,5,x)" | gp -q
15                          // 1+2+3+4+5

---

Javascript shells:

$ smjs
js> 25/3
8.333333333333334
js>

$ jspl
JSC: 25/3

RP: 8.33333333333333
RJS: [object Number]
JSC:
Good bye...

Answer 2

There are many ways to calculate. For simple expressions you can use bash itself:

echo $((20+5))

or expr:

expr 20 + 5

And for complex cases there is great tool bc:

echo "20+5" | bc

Btw, bc can calculate even very complex expression with roots, logarithms, cos, sin and so on.

Answer 3

The mentioned solutions are fine for very simple calculations, but very error-prone. Examples:

# without spaces 20+5 literally produces 20+5
expr 20+5
→ 20+5

# bc's result does't give the fractional part by default
bc <<<
9.0/2.0
→ 4

# expr does only integer
expr 9 / 2
→ 4

# same for echo
echo $((9/2))
→ 4

# echo chokes on floats
echo $((9.0/2.0))
→ bash: 9/2.0: syntax error: invalid arithmetic operator (error token is ".0")

# expr also has problems with floats
expr 9.0 / 2.0
→ expr: non-integer argument

A syntax error like the last ones never get unnoticed, but integer responses with a discarded float part can easily get unnoticed and lead to wrong results.

That's why I always use a scripting language like Lua for that. But you can choose any scripting language that you're familiar with. I just use Lua as an example. The advantages are

• a familiar syntax
• familiar functions
• familiar caveats
• flexible input
• spaces usually don't matter
• floating point output

Examples:

lua -e "print(9/2)"
→ 4.5

lua -e "print(9 / 2)"
→ 4.5

lua -e "print(9.0/2)"
→ 4.5

lua -e "print (9 /2.)"
→ 4.5

lua -e "print(math.sqrt(9))"
→ 3

Answer 4

You could use bc. E.g.,

$ echo "25 + 5" | bc
30

Alternatively bc <<< 25+5 will also work.

Or interactively, if you want to do more than just a single simple calculation:

$ bc
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'. 
25 + 5
30

bc -q will jump into bc right away without the header/copyright info. For more information see the bc man page

This page also shows how to set up an alias or function to do calculation like this:

c "25 + 5" 

and get the result

Answer 5

You can use calc:

If you just enter calc with no other arguments it enters an interactive mode where you can just keep doing math. You exit this by typing exit:

C-style arbitrary precision calculator (version 2.12.3.3)
Calc is open software. For license details type:  help copyright
[Type "exit" to exit, or "help" for help.]

; 2+4
6
; 3+5
8
; 3.4+5
8.4
; 2^4
16
; exit

Or you use it with the expression as an argument and it will provide the answer and then exit

$calc 2 + 4
    6
$

calc is similar to bc, I just like the way it behave as default better

Answer 6

I like to fire up Python and use it as an interactive calculator (but then again, I'm a Python programmer).

Answer 7

Since no-one else has mentioned it, and though it's not strictly a calculator (but neither are all these general-purpose scripting languages), I'd like to mention units:

$ units "1 + 1"
        Definition: 2
$ units "1 lb" "kg"
        * 0.45359237
         / 2.2046226

Or, for less output so you can get just the number to use in $() to assign to something:

$ units -t "1 + 1"
2
$ units -t "1 lb" "kg"
0.4539237

And it even does temperature conversions

$ units -t "tempC(20)" "tempF"
68

To get the temperature conversion in an expression for further calculation, do this:

$ units -t "~tempF(tempC(20))+1"
68.1

Answer 8

$> ghc -e '20 + 5'
25
it :: Integer

Answer 9

Nobody has mentioned awk yet? I made a little script I call "calc" with the following contents:

#!/bin/bash

awk "BEGIN {
  print $*
}"

Then just execute things like calc 1+1 or calc 5/2

Answer 10

I can't believe to read "the power of JavaScript" (but I had to upvote the answer for the other parts, except perl of course.

Practically, for the simple cases where integer arithmetic is sufficient, I use the buildin $((...)) and recommend it. Else, in almost all cases echo "..." | bc is sufficient.

For some arithmetic operations like statistics, matrix operations and more R is the better tool:

echo 25 + 5 | R --vanilla

and for small datasets and graphical throw away results, oocalc is a nice utility.

Answer 11

I use a little python script that will evaluate a python expression and print the result, then I can run something like

$ pc '[i ** 2 for i in range(10)]'
[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

the script is:

#!/usr/local/bin/python3

import sys
import traceback
from codeop import CommandCompiler

compile = CommandCompiler()
filename = "<input>"
source = ' '.join(sys.argv[1:]) + '\n'

try:
    code = compile(source, filename) 
except (OverflowError, SyntaxError, ValueError):
    type, value, sys.last_traceback = sys.exc_info()
    sys.last_type = type
    sys.last_value = value
    if filename and type is SyntaxError:
        # Work hard to stuff the correct filename in the exception
        try:
            msg, (dummy_filename, lineno, offset, line) = value.args
        except ValueError:
            # Not the format we expect; leave it alone
            pass
        else:
            # Stuff in the right filename
            value = SyntaxError(msg, (filename, lineno, offset, line))
            sys.last_value = value
    lines = traceback.format_exception_only(type, value)
    print(''.join(lines))
else:
    if code:
        exec(code)
    else:
        print('incomplete')

Unfortunately I don't remember where I borrowed most of the code from, so I can't cite it.

Answer 12

For console calculations, I use concalc. (sudo aptitude install concalc)

After that, just type concalc and hit enter. It won't supply a prompt, but just type in the your calculation (no spaces) and hit enter, and on the next line, it'll give you the numeric value.

Answer 13

SQLite:

echo 'select 1 + 1;' | sqlite3 

MySQL:

mysql -e 'select 1 + 1 from dual;'

PostgreSQL:

psql -c 'select 1 + 1 as sum;'

Answer 14

If you're stuck with just a C compiler, you can do something along the lines of this:

$ gcc -x c - <<EOF
#include <stdio.h>
int main() {
    printf("%f", 20.0+(5.0/2.0));
    return 0;
}
EOF
$ ./a.out