bc

[Nobody's Hero]

Good Morning,
I have written a script that reads a log file, calls 'ex' to edit what I need. Then I gather some backup stats and I need to do some division. How can I use bc in a script to devide, lets say, 400GB took 12 hours. Can I just call 'bc' and do the math?
bc
400 / 12
Or is there another way to calculate numbers?

Thanks,
Bob

[harry d brown jr · Accepted solution]

Robert,

Check this out:

bdf | grep -v Filesystem|grep vg02 | tr -s " " " "|cut -d" " -f 3 | sort -n | xargs echo | sed "s/ / + /g" | bc

or

echo `ls -l /tmp/va4_ioscan`"\nx x x x .65" | tr -s " " " "|cut -d" " -f 5 | xargs echo | sed "s/ / \* /g"|bc|cut -d"." -f1|sed "s/$/ \/ 512 /"|bc|sed "s:^:dd if=/t
mp/va4_ioscan of=/tmp/stewcount=:" | sh



live free or die
harry

[Andreas Voss]

Hi,

bc can used ie:

value=400
result=`echo "scale=2\n$value/12"|bc`

Regards

[Peter Kloetgen]

Hi Robert,

there are some more ways to calculate:

1) the "expr" command, has the following syntax: expr nr1 operator nr2
possible operators are: addition +
subtraction -
multiplication \*
division /
for example: expr 2 \* 5
# 10

please remember, this command can only calculate integers, so expr 10 / 6 would deliver an output of 1 !

2) (( nr1 operator nr2 )), has the same functions than expr, but is done a lot of faster. Same limitations than expr, no floating point!

3) awk has also a lot of numeric builtin- functions. To use it with variable=value, you call it awk -v variable=value, then the variable is a predefined in the awk- program. The awk- command has some numeric functions which can handle floating point.

Allways stay on the bright side of life!

Peter

[Robin Wakefield]

Hi Bob,

If you have perl:

perl -e 'print (eval ($ARGV[0]),"\n")' 400/12
33.3333333333333

or whatever.

Rgds, Robin.

[harry d brown jr]

Robert,

If you use the "-l" (dash-el) option, you get a decimals:

[root]pbctst: echo "400 / 12" | bc -l
33.33333333333333333333
[root]pbctst:


live free or die
harry

[James R. Ferguson]

Hi Robert:

'bc' works quite well. For decimal numbers, include the "scale":

# X=1;Y=8;echo "scale=3\n $X/$Y"|bc

I, too, like 'awk' given its ability to format and produce output in different number bases:

# X=1;Y=8;echo "$X $Y"|awk '{printf "%.4f\n",$1/$2}'

# X=7;Y=8;echo "$X $Y"|awk '{printf "%4x\n",$1+$2}'

For simple integer arithmetic, you can use the shell 'let':

# let A=100;let B=8;let C=$A/$B;echo $C

Regards!

...JRF...

[Steve Steel]

Hi


BC is fine.

Example
#!/usr/bin/sh
#You could use the 'two way pipe' to the program to do all your math operations,
like this:
# This starts bc with a two-way pipe
bc |&
# print -p writes to the pipe
print -p scale=4
print -p 3/4
# read -p reads from the pipe
read -p myvar
echo $myvar

bc tutorial in Number Processing Users Guide


Steve Steel

[Nobody's Hero]

Thanks Everyone,
Lots of great ideas that I will use.

Thanks,
Again,
Bob