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接上篇「将字节数转换成用户可读的格式」，上篇文章主要是使用Linux下已有的工具(numfmt，需要GNU coreutils >= 8.21)进行转换，但是我记录这篇文章的最初目的是自己编码实现相关功能（比如写成一个alias/function放在.bashrc中方便日常使用），这篇文章的内容就是介绍通过各种编程语言来实现该功能。

参考解答：

1.awk/gawk

# OK
echo "12454162221" | awk '
    BEGIN {
       split("B,KB,MB,GB,TB", Units, ",");
    }
    {
       u = 1;
       while ($1 >= 1024) {
          $1 = $1 / 1024;
          u += 1
       }
       $1 = sprintf("%.2f %s", $1, Units[u]);
       print $0;
    }
'

# OK
echo "12454162221" | gawk 'BEGIN { split("KMGTPEZY",suff,//)}
{
  match($0,/([0-9]+)/,bits)
  sz=bits[1]+0
  i=0; while ((sz>1024)&&(i<length(suff))) { sz/=1024;i++ }
  if (i) printf("%.3f %siB\n",sz,suff[i])
  else   printf("%3i B\n",sz)
}'

# OK
echo "12454162221" | awk '{
  xin=$1;
  if(xin==0) {
    print "0 B";
  } else {
    x=(xin<0?-xin:xin);
    s=(xin<0?-1:1);
    split("B KiB MiB GiB TiB PiB",type);
    for(i=5;y < 1;i--) {
      y=x/(2^(10*i));
    }
    print y*s " " type[i+2];
  };
}'

2.Perl

echo "12454162221" | perl -ne 'if (/^(\d+)/){$l=log($1+.1);$m=int($l/log(1024)); printf("%6.1f\t%s\n",($1/(2**(10*$m))),("K","M","G","T","P")[$m-1]);}'

# 最大以G为单位
echo "12454162221" | perl -pe 's{([0-9]+)}{sprintf "%.1f%s", $1>=2**30? ($1/2**30, "G"): $1>=2**20? ($1/2**20, "M"): $1>=2**10? ($1/2**10, "K"): ($1, "")}e'

3.Python

def bytes_format(filesize, unit=1024):
    unit = float(unit)
    for count in ['Bytes','KB','MB','GB', 'TB', 'PB']:
        if 0 < filesize < unit:
            return '{0:.3f} {1}'.format(filesize, count)
        filesize /= unit

print bytes_format(12454162221)

4.PHP

<?php

function bytes_format($numbers, $bytesize = 1024) {
   $readable = array("",  "KB", "MB", "GB", "TB", "PB");
   $index = 0;
   while($numbers > $bytesize){
      $numbers /= $bytesize;
      $index++;
   }
   return("".round($numbers, 2)." ".$readable[$index]);
}
echo bytes_format(12454162221) . "\n";
echo bytes_format(124541622210) . "\n";
echo bytes_format(1245416222100) . "\n";

参考链接：

• http://unix.stackexchange.com/questions/44040/a-standard-tool-to-convert-a-byte-count-into-human-kib-mib-etc-like-du-ls1
• http://stackoverflow.com/questions/15854332/file-size-in-human-readable-format
• http://www.kossboss.com/linux—bytes-to-human-readable-command
• http://ram.kossboss.com/humanbytesawk/
• http://ram.kossboss.com/linux-bytes-to-human-readable-command/
• http://superuser.com/questions/553976/how-to-display-the-size-in-human-readable-format-in-the-find-command/554027#554027
• http://serverfault.com/questions/62411/how-can-i-sort-du-h-output-by-size
• http://codesnippets.fesslersoft.de/format-bytes-to-human-readable-size/
• http://www.developerfeed.com/how-convert-bytes-human-readable-string-format-php/
• http://www.ivankristianto.com/tips-convert-your-numbers-to-human-readable-format/

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