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bash and math division problem

Hi all,

I did some scripting that counts total input and output traffic of eth0 from my iptables ...

I'm stuck with a nasty problem now.

# Name of the result file
STDIN=result

#Cat the file
CAT=$(cat $STDIN)

#RRD moet de waarden maar optellen met COUNTER
#Put the output one after the other separated with blank spaces and make a #white space a + sign
REPLACE=$(echo $CAT | sed -e s/\ /+/)

# Do some incrementing calc /1048576 for Mbytes /1024 for Kbytes
let z=$REPLACE
echo $z #<-- this gives a nice output of my input + my output

echo
echo Result in Kbytes
echo `expr $z / 1024` # here i'm dividing it to have kbytes value

echo
echo Result in Mbytes
echo `expr $z / 1048576`# same for mb

Cause now it works but he's modding the division eg . $z / 1048576 = 456,564214654 and he makes 456 of it if you get my point.... that's a loss in monitorring of half a megabyte !

This causes a massive difference after 30 days of monitorring the traffic !

Can anyone help me out please !

thx a lot !

send the numbers to bc(1) to do the division. Make sure you set the precision though. (read the man page its good)

You can use expr to return the remainder of division (i.e. the number of bytes left over) using % instead of /

Code:

echo Result in Kbytes

echo -n `expr $z / 1024`

echo -n " kb and "

echo -n `expr $z % 1024`

echo " bytes"

Alternativly, try using a calculator tool like bc instead of expr.

thx a lot

I decided to use bc, cause i need to update those values in my Round Robin database ...

did some searching and found following simple example :

bc cal.txt = Would result in 3, see below notes.

Within the cal.txt file you could have a simple statement such as:

/* Add the value 1+2 /*
1+2
quit

When running the above command you will receive the results of the cal.txt file. Which in this case would be 3.

well i made a file gave it 777 permission to be sure and when i do bc cal.txt = i get :

bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
File = is unavailable.

does anyone have a clue :p, i tried to read the manpages, but without examples it's a little too hard for me

thx for helping me out that fast

found it allreade :

i = 7 / 3
i
quit

when you runt that script using bc -l u will get floating point value in return :)

just wondering how to simplify to JUST 3 numbers after the , or . cause now i get 2.33333333333

th x!

hmmz found it as well :)

u have to put scale = 3 in top of ur script :)

this program rulez !!!

thx a lot guys for putting me on the right track