Perl & Python编写CGI-阿里云开发者社区

最近偶然玩了一下CGI，收集点资料写篇在这里留档。现在想做HTTP Cache回归测试了，为了模拟不同的响应头及数据大小，就需要一个CGI按需要传回指定的响应头和内容，这是从老外的测试页面学习到的经验。

CGI其实就是使用STDIN和环境变量作为输入, STDOUT做为输出，依照Http协议生成对应的数据。

一. 数据输出

数据输出遵循HTTP协议，分为四部分:

状态行 (Status Line):

200 OK

响应头(Response Headers):

Content-Type: text/html

Content-Length: 3072

空白行(代表响应头已经列完, 只能包含回车和换行符):

数据(文本或二进制数据):

<html>xxxxxx</html>

参考: HTTP Protocol

状态行和响应头中每一行都必须以\r\n(回车及换行)结束。使用这个规则，以简单的文本组装就可以完成响应了。

只要注意二进制数据输出方法就可以了。尝试设定Content-Length时可能没办法设定的准确，至少对于Apache Server是这样，不过不影响最后返回的数据量。

二. 数据输入

CGI的数据输入主要是环境变量，下面这个链接有一串定义,

CGI Environment Variables

Key	Value
DOCUMENT_ROOT	The root directory of your server
HTTP_COOKIE	The visitor's cookie, if one is set
HTTP_HOST	The hostname of the page being attempted
HTTP_REFERER	The URL of the page that called your program
HTTP_USER_AGENT	The browser type of the visitor
HTTPS	"on" if the program is being called through a secure server
PATH	The system path your server is running under
QUERY_STRING	The query string (see GET, below)
REMOTE_ADDR	The IP address of the visitor
REMOTE_HOST	The hostname of the visitor (if your server has reverse-name-lookups on; otherwise this is the IP address again)
REMOTE_PORT	The port the visitor is connected to on the web server
REMOTE_USER	The visitor's username (for .htaccess-protected pages)
REQUEST_METHOD	GET or POST
REQUEST_URI	The interpreted pathname of the requested document or CGI (relative to the document root)
SCRIPT_FILENAME	The full pathname of the current CGI
SCRIPT_NAME	The interpreted pathname of the current CGI (relative to the document root)
SERVER_ADMIN	The email address for your server's webmaster
SERVER_NAME	Your server's fully qualified domain name (e.g. www.cgi101.com)
SERVER_PORT	The port number your server is listening on
SERVER_SOFTWARE	The server software you're using (e.g. Apache 1.3)

当你需要CGI处理POST请求时，CGI就要使用STDIN做为输入来接收数据了。

在Perl里使用下面的代码读取:

use CGI;

my $cgi = CGI->new();

my %params = $cgi->Vars();

而在Python则是:

import cgi

cgi.FieldStorage()

参考: Perl CGI Input Test

三. 开发语言

可以写CGI的开发语言太多，下面附上两个分别使用Perl和Python编写的相同功能的CGI, 正好可以做个对比。

这两个脚本可以接收Query String, 然后返回不同的文件，数据大小，以及缓存相关的头信息，可以区分二进制数据和文本数据。

CGI脚本支持以Query String修改以下响应头:

content type,

cache control,

content length (只返回对应大小的数据),

last modified,

expires

下面是返回一个指定大小图片的例子:

/cgi/cache_factory.pl?type=image&size=32&last-modified=Fri, 02 Apr 2014 02:34:06 GMT&cache-control=private,max-age=60&expires=Fri, 22 Apr 2014 02:34:06 GMT

代码很简单，可以做个参考。

Perl版本

#!/usr/bin/perl
use strict;
use warnings;
use CGI;

use constant BUFFER_SIZE     => 4_096;
use constant DATA_DIRECTORY => "/var/www/Cache";

my $cgi = CGI->new();
my %params = $cgi->Vars();

&parserCommonHeaders;

if(exists $params{'type'} && $params{'type'}=="image"){
	&generateImageData;	    
 }
else{
	&generateTextData;
}

sub parserCommonHeaders{
	if(exists $params{'cache-control'}){
	  print 'Cache-Control:',$params{'cache-control'},"\r\n";  
	}

	 if(exists $params{'last-modified'}){
	   print 'Last-Modified:',$params{'last-modified'},"\r\n";  
	 }
	 
	 if(exists $params{'expires'}){
	   print 'Expires:',$params{'expires'},"\r\n";
	 }
	 
	 if(exists $params{'etag'}){
	   print 'ETag:ea6186e11526ce1:0',"\r\n";
	 }	
}

sub generateImageData{
	my $buffer = "";

	my $targetSize = 100*1024*1024;
	if(exists $params{'size'} && $params{'size'}>0){
		$targetSize = 1024*$params{'size'};
		print "Content-length: $targetSize \r\n";
	}

	my $image = DATA_DIRECTORY .'/images/very_big.jpg';
	my( $type ) = $image =~ /\.(\w+)$/;
	$type eq "jpg" and $type == "jpeg";
	
	print $cgi->header( -type => "image/$type", -expires => "-1d" );
	binmode STDOUT;
	
	local *IMAGE;
	open IMAGE, $image or die "Cannot open file $image: $!";
	
	my $sentSize = 0;
	while ( read( IMAGE, $buffer, BUFFER_SIZE ) ) {
	    print $buffer;
	    $sentSize += BUFFER_SIZE;
	    
	    if($sentSize>=$targetSize){
	    	last;
	    }
	}
	close IMAGE;
}

sub generateTextData{
	my $startHeader = '<html><head><title>HTTP Cache Testing HTML</title></head><body>';
	my $tailPart = '</body></html>';
	
	if(exists $params{'type'}){
		print "Content-type:$params{'type'}\r\n";
	}
	else{
		print "Content-type:text/html\r\n";
	}

	my $targetTextSize = 100*1024*1024;
	if(exists $params{'size'} && $params{'size'}>0){
		$targetTextSize = 1024*$params{'size'};
		print "Content-length: $targetTextSize \r\n";
	}
	print "\r\n";
	
	$targetTextSize -= length($startHeader) + length($tailPart);
	
	print "$startHeader";
	
	my $filepath = DATA_DIRECTORY .'/files/big_text.txt';
	
	open(FILE, $filepath) or die $!;
	my @lines = <FILE>;
	close(FILE);
	
	foreach my $line (@lines) {
    	if( length($line)<=$targetTextSize ){
    		print $line;
    	}
    	else{
    		print substr($line,0,$targetTextSize);
    	}
    	
    	$targetTextSize -= length($line);
    	
    	if($targetTextSize<=0){
    		last;
    	}
	}

	print "$tailPart";
}

Python版本

#!/usr/bin/python
import os 
import cgi
import sys

BUFFER_SIZE = 4096
DATA_DIRECTORY = "/var/www/Cache"

def parserCommonHeaders(formQuery):
  if('cache-control' in formQuery.keys()):
    print 'Cache-Control:',formQuery['cache-control'].value,"\r\n",  
  
  if('last-modified' in formQuery.keys()):
     print 'Last-Modified:',formQuery['last-modified'].value,"\r\n",  
   
  if('expires' in formQuery.keys()):
     print 'Expires:',formQuery['expires'].value,"\r\n",
   
  if('etag' in formQuery.keys()):
     print 'ETag:ea6186e11526ce1:0',"\r\n",


def generateImageData(formQuery):
  targetSize = 100*1024*1024;
  if('size' in formQuery.keys()):
    targetSize = 1024*int(formQuery['size'].value)
    print "Content-length:",targetSize,"\r\n",

  image = DATA_DIRECTORY+'/images/very_big.jpg'
  print "Content-Type:image/jpeg\r\n",
  
  print 

  sentSize = 0
  f = open(image, 'rb')
  while True:
    data = f.read(4096)
    sentSize = sentSize + BUFFER_SIZE
    sys.stdout.write(data)
    if sentSize>targetSize:
        break

  sys.stdout.flush()
  close(f)
  
 
def generateTextData(formQuery):
  startHeader = '<html><head><title>HTTP Cache Testing HTML</title></head><body>'
  tailPart = '</body></html>'
  
  targetTextSize = 2.3*1024*1024;
  if('size' in formQuery.keys()):
    targetTextSize = 1024*int(formQuery['size'].value)
    print "Content-length:",targetTextSize,"\r\n",
    
  if('type' in formQuery.keys()):
    print "Content-type: %s\r\n"%(formQuery['type'].value),
  else:
    print "Content-type: text/html\r\n",
      
  print
  
  print startHeader
  
  targetTextSize = targetTextSize - len(startHeader) - len(tailPart)
  
  filepath = DATA_DIRECTORY + '/files/big_text.txt'
  
  file = open(filepath)
  lines = file.readlines()
  file.close()
  
  for line in lines:
      if( len(line) <= targetTextSize ):
        print line
      else:
        print line[0:targetTextSize]
      
      targetTextSize = targetTextSize - len(line)
      
      if(targetTextSize<=0):
        break
  
  print tailPart

if __name__ =="__main__":
  formQuery = cgi.FieldStorage() #os.environ['QUERY_STRING']

  parserCommonHeaders(formQuery)

  if('type' in formQuery.keys() and formQuery['type'].value=="image"):
    generateImageData(formQuery)     
  else:
    generateTextData(formQuery)

四. 服务器

服务器端使用Apache Server+WANem, 配合CGI完成灵活的需求，开通SFTP端口供相关同学编辑，方便共享测试用例。

.-----. .-------.

| CGI | | WANem |

'-----'---'-------'

| Apache Server |

'-----------------'

SFTP & HTTP

.------------------.

| Web Page Editor |

| and Browser |

'------------------'

配有WANem最大的好处就是可以根据需求进网络状态调整, 甚至可以用类似下面的方式在测试用例动态调整。

参考:

Apache配置 (不要忘记给CGI脚本加上可执行权限)

CGI Programming 101 (Perl)

Debugging CGI Programs (Perl)

Python CGI编程

Python CGI Debugging

Perl & Python编写CGI

一. 数据输出

二. 数据输入

三. 开发语言

Perl版本

Python版本

四. 服务器

参考:

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Perl &amp; Python编写CGI

一. 数据输出

二. 数据输入

三. 开发语言

Perl版本

Python版本

四. 服务器

参考:

热门文章

最新文章

相关课程

相关电子书

相关实验场景

Perl & Python编写CGI