Simple Math Question

[rkasowan]

Hello all-

I've created a crazy script that I am so proud of except I can't figure out a simple math problem that is holding up the project.

I have a line in my script that produces a number with a decimal. In my case the number is 75.5. I can't get rid of the ".5". How do I round a number up or down?

It shouldn't be a big deal but my script errors out because the shell can't handle numbers with a ".".

How do I convert 75.5 to 75?

The line from my script is:

fsize=$((size / 1000261785))

and $fsize almost always has a decimal.

Any help would be greatly appreciated. Thanks in advance

[wje_lf]

That line from your script can't be accurate.

Wasn't there supposed to be a $ before the "size" in that line?

And just to make it easier for us to help you, can you post a tiny, complete script which misbehaves? Something which we can copy and paste into a window and experiment with for you?

Just a suggestion.

[jellystones]

Im not familiar with command-line scripting, but if there is a Math.floor() or Math.ceiling() function this should solve your problem. Or perhaps Math.round.

Or convert it to a string and get a substring from the beginning to the first instance of a decimal.

Hello all-

I've created a crazy script that I am so proud of except I can't figure out a simple math problem that is holding up the project.

I have a line in my script that produces a number with a decimal. In my case the number is 75.5. I can't get rid of the ".5". How do I round a number up or down?

It shouldn't be a big deal but my script errors out because the shell can't handle numbers with a ".".

How do I convert 75.5 to 75?

The line from my script is:

fsize=$((size / 1000261785))

and $fsize almost always has a decimal.

Any help would be greatly appreciated. Thanks in advance

[rkasowan]

I found a simple solution that met my needs:

#!/bin/tcsh -f
read v
echo $v/1 | bc
exit 0

Thanks for the input - I see a few new commands I need to check out.

-= robbie =-

[drl]

Hi.

We first note:

ARITHMETIC EVALUATION
The shell allows arithmetic expressions to be evaluated, under certain
circumstances (see the let builtin command and Arithmetic Expansion).
Evaluation is done in fixed-width integers ...

** exponentiation
* / % multiplication, division, remainder
+ - addition, subtraction

...
Shell variables are allowed as operands; parameter expansion is per-
formed before the expression is evaluated. Within an expression, shell
variables may also be referenced by name without using the parameter
expansion syntax.

-- excerpts from man bash under ARITHMETIC EVALUATION

and:

let: let arg [arg ...]
Each ARG is an arithmetic expression to be evaluated. Evaluation
is done in fixed-width integers with no check for overflow

As an example:

#!/usr/bin/env bash

# @(#) s1       Demonstrate arithmetic in shell.

set -o nounset
echo

debug=":"
debug="echo"

## Use local command version for the commands in this demonstration.

echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version bash

echo

x=7
echo " x is $x"

echo
echo " x/3 is $(( x/3 ))"

echo
echo " x / 3 is $(( x / 3 ))"

echo
echo " using \"let\":"
let y=x/2
echo " y is $y"

exit 0

Producing:

% ./s1

(Versions displayed with local utility "version")
GNU bash 2.05b.0

 x is 7

 x/3 is 2

 x / 3 is 2

 using "let":
 y is 3

See also the very valuable collection of explanations and examples in http://www.tldp.org/LDP/abs/html/arithexp.html , the Advanced Bash-Scripting Guide.

The sample above shows no decimal fractions, only truncation, as expected according to man bash.

As Bill suggested, if you are having problems -- such as getting decimals, as in 75.5 -- then please post the smallest script in its entirety that illustrates the problem.

Best wishes ... cheers, drl

---

Standard advice: Do not use csh family for scripting.