Answer by John for A standard tool to convert a byte-count into human KiB MiB etc; like du, ls1

This is a complete rewrite inspired by Peter.O's modified version of Gilles' awk script.

Changes:

• Fixes Peter.O's bug where he looks for a string of >1 character where he should be looking for one >4 characters. Due to that bug, his code doesn't work for ZiB units.
• Removes the very ugly hardcoding of a long string of space-separated unit sizes.
• Adds command line switches to enable/disable padding.
• Adds command line switches to go from base-1024 (KiB) to base-1000 (KB) notation.
• Wraps it all in an easy to use function.
• I place this in the public domain and welcome widespread use.

Code:

bytestohuman() {
    # converts a byte count to a human readable format in IEC binary notation (base-1024), rounded to two decimal places for anything larger than a byte. switchable to padded format and base-1000 if desired.
    local L_BYTES="${1:-0}"
    local L_PAD="${2:-no}"
    local L_BASE="${3:-1024}"
    BYTESTOHUMAN_RESULT=$(awk -v bytes="${L_BYTES}" -v pad="${L_PAD}" -v base="${L_BASE}" 'function human(x, pad, base) {
         if(base!=1024)base=1000
         basesuf=(base==1024)?"iB":"B"

         s="BKMGTEPYZ"
         while (x>=base && length(s)>1)
               {x/=base; s=substr(s,2)}
         s=substr(s,1,1)

         xf=(pad=="yes") ? ((s=="B")?"%5d   ":"%8.2f") : ((s=="B")?"%d":"%.2f")
         s=(s!="B") ? (s basesuf) : ((pad=="no") ? s : ((basesuf=="iB")?(s "  "):(s " ")))

         return sprintf( (xf " %s\n"), x, s)
      }
      BEGIN{print human(bytes, pad, base)}')
    return $?
}

Test Cases (if you want to look at the output):

bytestohuman 1; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 500; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1023; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1024; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1500; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000000; echo "${BYTESTOHUMAN_RESULT}.";

bytestohuman 1 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 500 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1023 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1024 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1500 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000 no 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000000 no 1000; echo "${BYTESTOHUMAN_RESULT}.";

bytestohuman 1 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 500 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1023 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1024 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1500 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000 yes; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000000 yes; echo "${BYTESTOHUMAN_RESULT}.";

bytestohuman 1 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 500 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1023 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1024 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 1500 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";
bytestohuman 150000000000000000000 yes 1000; echo "${BYTESTOHUMAN_RESULT}.";

Enjoy!