为什么在很多CGI脚本中需要空的echo / print行？
示例bash：
#!/bin/bash
echo "Content-type: text/html"
echo ''
echo 'CGI Bash Example'
示例python：
#!/usr/bin/env python
# -*- coding: UTF-8 -*-
# enable debugging
import cgitb
cgitb.enable()
print "Content-Type: text/plain;charset=utf-8"
print
print "Hello World!"