把ip地址转换为二进制的bash脚本

# 几个关键点:
#
# tr 替换字符串
# 循环遍历ip的每一位
# echo 指明 编码类型为二进制, 然后借助 bc 计算二级制的值
# TODO 从循环到awk的管道 没完全理解
# awk printf 的格式表示 为每个8为的二进制比特位前面加上"."
# "cut -c 2-" 表示 "Cut out everything from the 2rd character to the end of each line"

function ip2binary() {
  if [ $# -eq 0 ]; then
    echo "example";
    echo "ip_2_binary 192.168.31.178";
    echo "11000000.10101000.00011111.10110010";
    return 1;
  fi

  local ip=$1

  for i in $(echo ${ip} | tr '.' ' '); do
    echo "obase=2 ; $i" | bc;
  done | awk '{printf ".%08d", $1}' | cut -c 2-
}

　　ref: https://stackoverflow.com/questions/4042601/unixhow-to-convert-ip-address-to-binary-code