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Work the Shell - Breaking Numbers Down

Issue 152

From Issue #152
December 2006

Dec 01, 2006  By Dave Taylor
 in
A kilo of information on how to represent even giga numbers in a mega-useful way.
______________________

Dave Taylor has been hacking shell scripts for over thirty years. Really. He's the author of the popular "Wicked Cool Shell Scripts" and can be found on Twitter as @DaveTaylor and more generally at www.DaveTaylorOnline.com.

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Function for bigger numbers

Simon Sweetman's picture
Submitted by Simon Sweetman (not verified) on Fri, 09/17/2010 - 20:06.

Here is a little Korn Shell implementation based on your article that supports up to Yotta Bytes Yikes!

I thought I'd share it with your readers.

#!/bin/ksh
bytestohr()
{
    # Convert input parameter (number of bytes) 
    # to Human Readable form
    #
    SLIST="bytes,KB,MB,GB,TB,PB,EB,ZB,YB"

    POWER=1
    VAL=$( echo "scale=2; $1 / 1" | bc)
    VINT=$( echo $VAL / 1024 | bc )
    while [ $VINT -gt 0 ]
    do
        let POWER=POWER+1
        VAL=$( echo "scale=2; $VAL / 1024" | bc)
        VINT=$( echo $VAL / 1024 | bc )
    done

    echo $VAL$( echo $SLIST | cut -f$POWER -d, )
}

NOTE: It's tempting to use the shell internal maths instead of bc for more performance, but values over 8Gb aren't supported by the shell's 32bit integers.

Oops mistake above

Simon Sweetman's picture
Submitted by Simon Sweetman (not verified) on Fri, 09/17/2010 - 20:22.

As soon as you make a post you find a mistake, the above while statement should be changed to

while [ ! $VINT = "0" ]

To avoid numeric overflows in some Korn shell implementations.

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