CODEWITHSUNDEEP
bashparametersflags
George
George

Reputation: 21

How to use an expression as flag argument

Lets say I have

tmp0=2
let tmp=2*$tmp0+3  #randomm example

I can write $(cat something | cut -d " " -f$tmp), but what I want to know is how to write $(cat something | cut -d " " -f$(2*$tmp0+3))

Basically I want to know how use "mathematical expression" as a flag parameter

Upvotes: 0

Views: 34

Answers (1)

Jason
Jason

Reputation: 2671

You are actually pretty close:

$(cat something | cut -d " " -f$((2*tmp0+3)))

Note the (( and )). That is how it is done. Also, take notice that I didn't need the $ on the variable. Inside a mathematical expression, variables don't need $ and it acts a lot more like C. To get the value out of it, you do need the $ on the front of ((. If you don't need the value, but just the behavior, you can leave off the $. Here is another example of this:

for ((i=0; i < 10; ++i)); do
    echo $i
done

Since I didn't need the value out of the expression, I can leave out the $.

Upvotes: 1

Related Questions