Numerical Calculation in Unix:

[Sharvil Desai]

Hi,
I have a shell-script from which I do the calculation to find the size of a file in Mb.

SIZE=`ls -l x:/xyz/abc.dat|tr -s " "|cut -d " " -f 5`
SIZE=`expr $SIZE / 1024 / 1024`
However, this does not give me the precise size of the file. It chops off the digits after the decimal point. Can someone please tell me how to preserve two digits after the decimal? Thank you.

[A. Clay Stephenson · Accepted solution]

The shell (or expr) only does integer arithmatic so your plan is doomed. You need to use awk, bc, or Perl.

Here is an awk equivalent:

SIZE=$(ls -l /xyz/abc.dat | awk '{ printf("%8.2f\n",($5 + 0) / (1024 * 1024)) }')
echo "Size = ${SIZE}"

Note: The $5 + 0 was intentional; it forces the argument into numerical context -- a standard awk idiom.

[Hein van den Heuvel]

perl -e 'printf "%8.3f MB\n", (-s "x.x") / (1024*1024)'

or with some more stuff like a size filter around it:

perl -e 'while (<*.trc>) { $s= -s; printf "%8.3f %s\n", $s/(1024*1024), $_ if $s > 999999}'

hth,
Hein.

[Sharvil Desai]

I will use the awk version, since I don't have perl. But thank you both for posting your answers!