artimetic in shell??

[Linux_cat]

IS there a command that will let you do arithmetic in shell?? e.g

1 * 100 - 56 / 7

thanks dudes.

[the.spike]

Check out the expr command.. man expr

It should do what you want..

There's also a syntax that looks like ((...)) where the maths goes between the brackets..

spike...

[Pierre Lambion]

Why not use bc ? You probably want to set the decimals in a config file.

P.

[Linux_cat]

thanks for your help, i am using the let comman but have a little prob I cant get the following script to work

#!/bin/ksh

YMOUT15=${1:?"requires an argument" }

line_count=$(zcat $YMOUT15|wc -l)

echo $line_count

percentage=$(let "line_count/100")

echo $percentage

percentage_15=$(let "percentage*15")

echo $percentage_15

zcat $YMOUT15 > YMOUTSPLIT15

split -l $percentage_15 YMOUTSPLIT 15


it seems my variables are not passing into the let commands, what am I doing wrong??.

[the.spike]

Your script wants to be more like this :

#!/bin/ksh
YMOUT15=${1:?"requires an argument" }
line_count=$(zcat $YMOUT15|wc -l)
echo $line_count
let percentage="${line_count}/100"
echo $percentage
let percentage_15="${percentage}*15"
echo $percentage_15
zcat $YMOUT15 > YMOUTSPLIT15
split -l $percentage_15 ${YMOUTSPLIT} 15

I've hi-lighted the changes that I've made. Your let construct was wrong and you weren't qualifying your variables properly.

spike...

[bsh152s]

I don't believe "let" will let you divide. Well, it will, but it will truncate the decimal. Use bc instead.

[the.spike]

Originally posted by bsh152s
I don't believe "let" will let you divide. Well, it will, but it will truncate the decimal. Use bc instead.

True enough about "let" but then in this case the decimal is not important.

To be honest, if it was me, I'd have probably done the maths in awk.. don't know why, that's just what I do sometimes..

percentage_15=$( echo "$line_count | awk '{ printf (" %d\n", ( $1 \ 100 ) * 15 ) }' )

[Architect]

Wow! I had never heard of this command before. What exactly does the 'let' command do?
Hmm..... 'let' me try a 'man let' :p

[Linux_cat]

Thanks for the help people, much appreciated. I completed the script as below using the (()) braackets, although i may now re-write it using the awk method, thats way cool:

#!/bin/ksh

YMOUT15=${1:?"requires an argument" }

line_count=$(cat $YMOUT15|wc -l)

echo $line_count

percentage=$(((line_count/100)))

echo $percentage

percentage_15=$(((percentage*15)))

echo $percentage_15

cat $YMOUT15 > YMOUT15SPLIT
split -l $percentage_15 YMOUT15SPLIT 15

[bwkaz]

Originally posted by Linux_cat
although i may now re-write it using the awk method, thats way cool Cool, maybe. But it wastes a process every time you start up awk. ;) Doing arithmetic in bash with $((...)) doesn't waste a process. And as long as you don't need fractional precision or arbitrarily large numbers, it'll work just as well.