how to perform a basic arithmetics from unix csh/tcsh shell

Question

Under windows, when I need to perform a basic calculations, I use a built-in calculator. Now I would like to find out what is the common way if you only have a shell.

Thanks

Answer 1

And you can always use the python interpreter, it's normally included in linux distros.

http://docs.python.org/tutorial/introduction.html#using-python-as-a-calculator

$ python
Python 2.6.2 (r262:71605, Apr 14 2009, 22:40:02) [MSC v.1500 32 bit (Intel)]
Type "help", "copyright", "credits" or "license" for more information.
>>> 2+2
4
>>> # This is a comment
... 2+2
4
>>> 2+2  # and a comment on the same line as code
4
>>> (50-5*6)/4
5
>>> # Integer division returns the floor:
... 7/3
2
>>> 7/-3
-3
>>> # use float to get floating point results.
>>> 7/3.0
2.3333333333333335

The equal sign ('=') is used to assign a value to a variable. Afterwards, no result is displayed before the next interactive prompt:

>>> width = 20
>>> height = 5*9
>>> width * height
900

And of course there's the math module which should solve most of your calculator needs.

>>> import math
>>> math.pi
3.1415926535897931
>>> math.e
2.7182818284590451
>>> math.cos() # cosine
>>> math.sqrt()
>>> math.log()
>>> math.log10()

Answer 2

From this web page (for csh and derivatives, since you asked):

% @ x = (354 - 128 + 52 * 5 / 3)
% echo Result is $x
Result is 174

and

% set y = (354 - 128 + 52 / 3)
% echo Result is $y
Result is 354 - 128 + 52 / 3

notice the different results.

Personally, I stick to /bin/sh and call awk or something (for maximal portability), or others have exhibited the bash approach.

Answer 3

You can use dc. Or bc.

Answer 4

There are many good solutions given here, but the 'classic' way to do arithmetic in the shell is with expr.

Answer 5

Bash supports basic (integer only) arithmetic inside $(( )):

$ echo $(( 100 / 3 ))
33
$ myvar="56"
$ echo $(( $myvar + 12 ))
68
$ echo $(( $myvar - $myvar ))
0
$ myvar=$(( $myvar + 1 ))
$ echo $myvar
57

(example copied straight from the IBM link)

• More in-depth discussion of bash arithmetic

Answer 6

If you're using bash, here's a handy example of a small shell script that allows you to do calculations from the command line (including specifying precision for floating-point numbers):

http://www.novell.com/coolsolutions/tools/17043.html

Answer 7

You can also use Perl easily where bc or expr are not powerful enough:

$ perl5.8 -e '$a=1+2; print "$a\n"' 
3

Answer 8

Alternative option is to use the built in BC command