UNIX for Dummies Questions & Answers

I have 2 variables

a=2
b=1

i want to add a and b

how do i do this in unix using just the echo command and by assigning it to a different variable like c?

ant:/home/vbe $ more tutu
a=2
b=1
let c=a+b
echo "a: "$a " b: "$b " c: "$c
ant:/home/vbe $ sh tutu
a: 2 b: 1 c: 3

Thanks!

For what it's worth, I've found the awk method very handy. As an unnecessarily complex example:

Code:

echo 13 12 22 30 44 | awk '{print $1 * $2 + $3 / cos($4) + $5 / 3}'

It makes it very easy to build a formula and feed numbers into it. For example, suppose I typo'ed and want the cosine of 35 instead of 30. I just arrow up, change the 30 to 35, and I'm done. Or, alternately, ^30^35. My work involves loads of math geekery, so this has become very handy.

The expr function in unix will help to add the values.

c=`expr $a + $b`
echo $c

Code:

[rick ~]$ a=2
[rick ~]$ b=1
[rick ~]$ c=$(($a + $b))
[rick ~]$ echo $c
3
[rick ~]$

These methods are very good, but when you are going for float addition i.e. 1.3+3.4 then it won't work.