Perl 简明教程

Perl - CGI Programming

What is CGI ?

  1. A Common Gateway Interface, or CGI, is a set of standards that defines how information is exchanged between the web server and a custom script.

  2. The CGI specs are currently maintained by the NCSA and NCSA defines CGI is as follows −

  3. The Common Gateway Interface, or CGI, is a standard for external gateway programs to interface with information servers such as HTTP servers.

  4. The current version is CGI/1.1 and CGI/1.2 is under progress.

Web Browsing

要了解 CGI 的概念，让我们看看当我们单击某个网页上可用的超链接来浏览某个特定网页或 URL 时会发生什么。

To understand the concept of CGI, lets see what happens when we click a hyper link available on a web page to browse a particular web page or URL.

  1. Your browser contacts web server using HTTP protocol and demands for the URL, i.e., web page filename.

  2. Web Server will check the URL and will look for the filename requested. If web server finds that file then it sends the file back to the browser without any further execution otherwise sends an error message indicating that you have requested a wrong file.

  3. Web browser takes response from web server and displays either the received file content or an error message in case file is not found.

然而，有可能以这样的方式设置 HTTP 服务器，以便每当请求某个目录中的文件时，该文件不会被发送回来；而会被作为程序执行，并且无论该程序生成什么结果，都将发送回来让您的浏览器显示。这可以通过使用 Web 服务器中可用的特殊功能来完成，它被称为 Common Gateway Interface 或 CGI，而由服务器执行以产生最终结果的此类程序被称为 CGI 脚本。这些 CGI 程序可以是 PERL 脚本、Shell 脚本、C 或 C++ 程序等。

However, it is possible to set up HTTP server in such a way so that whenever a file in a certain directory is requested that file is not sent back; instead it is executed as a program, and whatever that program outputs as a result, that is sent back for your browser to display. This can be done by using a special functionality available in the web server and it is called Common Gateway Interface or CGI and such programs which are executed by the server to produce final result, are called CGI scripts. These CGI programs can be a PERL Script, Shell Script, C or C++ program, etc.

CGI Architecture Diagram

cgiarch

Web Server Support and Configuration

在继续 CGI 编程之前，请确保您的 Web 服务器支持 CGI 功能，并且已配置为处理 CGI 程序。由 Web 服务器执行的所有 CGI 程序都保存在预先配置的目录中。此目录被称为 CGI 目录，按照惯例它被命名为 /cgi-bin。按照惯例，Perl CGI 文件将扩展名为 .cgi 。

Before you proceed with CGI Programming, make sure that your Web Server supports CGI functionality and it is configured to handle CGI programs. All the CGI programs to be executed by the web server are kept in a pre-configured directory. This directory is called CGI directory and by convention it is named as /cgi-bin. By convention Perl CGI files will have extention as .cgi.

First CGI Program

这里有一个简单的链接，它链接到一个名为 hello.cgi 的 CGI 脚本。该文件保存在 /cgi-bin/ 目录中，并且具有以下内容。在运行您的 CGI 程序之前，请确保您已使用 chmod 755 hello.cgi UNIX 命令更改了该文件模式。

Here is a simple link which is linked to a CGI script called hello.cgi. This file has been kept in /cgi-bin/ directory and it has the following content. Before running your CGI program, make sure you have change mode of file using chmod 755 hello.cgi UNIX command.

#!/usr/bin/perl

print "Content-type:text/html\r\n\r\n";
print '<html>';
print '<head>';
print '<title>Hello Word - First CGI Program</title>';
print '</head>';
print '<body>';
print '<h2>Hello Word! This is my first CGI program</h2>';
print '</body>';
print '</html>';

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现在，如果您单击 hello.cgi 链接，那么请求会发送到在 /cgi-bin 目录中搜索 hello.cgi 的 Web 服务器，执行它，并且无论生成了什么结果，Web 服务器都会将该结果发送回 Web 浏览器，如下所示：

Now if you click hello.cgi link then request goes to web server who search for hello.cgi in /cgi-bin directory, execute it and whatever result got generated, web server sends that result back to the web browser, which is as follows −

Hello Word! This is my first CGI program

hello.cgi 脚本是一个简单的 Perl 脚本，它正在向 STDOUT 文件（即屏幕）写入其输出。还有一个重要的额外功能可用，即要打印的第一行 Content-type:text/html\r\n\r\n 。这一行发送回浏览器并指定要显示在浏览器屏幕上的内容类型。现在您必定已经了解了 CGI 的基本概念，并且可以使用 Perl 编写许多复杂的 CGI 程序。此脚本还可以与任何其他外部系统进行交互，以交换信息，如数据库、网络服务或任何其他复杂界面。

This hello.cgi script is a simple Perl script which is writing its output on STDOUT file, i.e., screen. There is one important and extra feature available which is first line to be printed Content-type:text/html\r\n\r\n. This line is sent back to the browser and specifies the content type to be displayed on the browser screen. Now you must have undertood basic concept of CGI and you can write many complicated CGI programs using Perl. This script can interact with any other exertnal system also to exchange information such as a database, web services, or any other complex interfaces.

Understanding HTTP Header

第一行 Content-type:text/html\r\n\r\n 是 HTTP 标头的一部分，发送到浏览器，以便浏览器可以理解来自服务器端的传入内容。所有 HTTP 标头都将采用以下形式 −

The very first line Content-type:text/html\r\n\r\n is a part of HTTP header, which is sent to the browser so that browser can understand the incoming content from server side. All the HTTP header will be in the following form −

HTTP Field Name: Field Content

例如 −

For Example −

Content-type:text/html\r\n\r\n

有其他一些重要的 HTTP 头信息，您将在 CGI 编程中经常使用。

There are few other important HTTP headers, which you will use frequently in your CGI Programming.

Sr.No.

Header & Description

1

Content-type: String A MIME string defining the format of the content being returned. Example is Content-type:text/html

2

Expires: Date String The date when the information becomes invalid. This should be used by the browser to decide when a page needs to be refreshed. A valid date string should be in the format 01 Jan 1998 12:00:00 GMT.

3

Location: URL String The URL that should be returned instead of the URL requested. You can use this filed to redirect a request to any other location.

4

Last-modified: String The date of last modification of the file.

5

Content-length: String The length, in bytes, of the data being returned. The browser uses this value to report the estimated download time for a file.

6

Set-Cookie: String Set the cookie passed through the string

CGI Environment Variables

所有 CGI 程序都将能够访问以下环境变量。这些变量在编写任何 CGI 程序时发挥着重要作用。

All the CGI program will have access to the following environment variables. These variables play an important role while writing any CGI program.

Sr.No.

Variables Names & Description

1

CONTENT_TYPE The data type of the content. Used when the client is sending attached content to the server. For example file upload, etc.

2

CONTENT_LENGTH The length of the query information. It’s available only for POST requests

3

HTTP_COOKIE Returns the set cookies in the form of key & value pair.

4

HTTP_USER_AGENT The User-Agent request-header field contains information about the user agent originating the request. Its name of the web browser.

5

PATH_INFO The path for the CGI script.

6

QUERY_STRING The URL-encoded information that is sent with GET method request.

7

REMOTE_ADDR The IP address of the remote host making the request. This can be useful for logging or for authentication purpose.

8

REMOTE_HOST The fully qualified name of the host making the request. If this information is not available then REMOTE_ADDR can be used to get IR address.

9

REQUEST_METHOD The method used to make the request. The most common methods are GET and POST.

10

SCRIPT_FILENAME The full path to the CGI script.

11

SCRIPT_NAME The name of the CGI script.

12

SERVER_NAME The server’s hostname or IP Address.

13

SERVER_SOFTWARE The name and version of the software the server is running.

这里是列出 Web 服务器支持的所有 CGI 变量的小型 CGI 程序。单击此链接 Get Environment 查看结果

Here is a small CGI program to list down all the CGI variables supported by your Web server. Click this link to see the result Get Environment

#!/usr/bin/perl

print "Content-type: text/html\n\n";
print "<font size=+1>Environment</font>\n";
foreach (sort keys %ENV) {
   print "<b>$_</b>: $ENV{$_}<br>\n";
}

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Raise a "File Download" Dialog Box?

有时，您希望提供一个选项，用户单击该选项将看到一个“文件下载”对话框，而不是显示实际内容。这非常简单，通过 HTTP 头可以实现。

Sometime it is desired that you want to give option where a user will click a link and it will pop up a "File Download" dialogue box to the user instead of displaying actual content. This is very easy and will be achived through HTTP header.

此 HTTP 头与前面部分中提到的头不同。例如，如果您想让某个 FileName 文件可从给定链接下载，则其语法如下：

This HTTP header will be different from the header mentioned in previous section. For example, if you want to make a FileName file downloadable from a given link then it’s syntax will be as follows −

#!/usr/bin/perl

# HTTP Header
print "Content-Type:application/octet-stream; name = \"FileName\"\r\n";
print "Content-Disposition: attachment; filename = \"FileName\"\r\n\n";

# Actual File Content will go hear.
open( FILE, "<FileName" );
while(read(FILE, $buffer, 100) ) {
   print("$buffer");
}

GET and POST Methods

您肯定遇到过许多情况，您需要将某些信息从浏览器传递到 Web 服务器，最终传递到处理您请求的 CGI 程序中。浏览器最常使用两种方法将此信息传递到 Web 服务器上。这两种方法是 GET 方法和 POST 方法。让我们逐一了解它们。

You must have come across many situations when you need to pass some information from your browser to the web server and ultimately to your CGI Program handling your requests. Most frequently browser uses two methods to pass this information to the web server. These methods are GET Method and POST Method. Let’s check them one by one.

Passing Information using GET Method

GET 方法将编码的用户信息追加到页面 URL 本身。该页面和编码信息由 ? 字符分隔，如下所示：

The GET method sends the encoded user information appended to the page URL itself. The page and the encoded information are separated by the ? character as follows −

http://www.test.com/cgi-bin/hello.cgi?key1=value1&key2=value2

GET 方法是将信息从浏览器传递到 Web 服务器的默认方法，它会生成一个长字符串，显示在浏览器的 Location: 框中。如果您有密码或其他要传递给服务器的敏感信息，则绝不应使用 GET 方法。GET 方法有大小限制：请求字符串中仅能传递 1024 个字符。

The GET method is the defualt method to pass information from a browser to the web server and it produces a long string that appears in your browser’s Location:box. You should never use GET method if you have password or other sensitive information to pass to the server. The GET method has size limitation: only 1024 characters can be passed in a request string.

此信息使用 QUERY_STRING 头传递，并可通过 QUERY_STRING 环境变量在你的 CGI 程序中访问，可以在你的 CGI 程序中解析和使用。

This information is passed using QUERY_STRING header and will be accessible in your CGI Program through QUERY_STRING environment variable which you can parse and use in your CGI program.

您可以简单地将键值对与任何 URL 连接起来传递信息，也可以使用 HTML <FORM> 标记使用 GET 方法传递信息。

You can pass information by simply concatenating key and value pairs alongwith any URL or you can use HTML <FORM> tags to pass information using GET method.

Simple URL Example: Get Method

下面是一个简单的 URL，它将两个值传递给 hello_get.cgi 程序，并使用 GET 方法。

Here is a simple URL which will pass two values to hello_get.cgi program using GET method.

下面是 hello_get.cgi 脚本，用于处理 Web 浏览器给出的输入。

Below is hello_get.cgi script to handle input given by web browser.

#!/usr/bin/perl

local ($buffer, @pairs, $pair, $name, $value, %FORM);
# Read in text
$ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/;
if ($ENV{'REQUEST_METHOD'} eq "GET") {
   $buffer = $ENV{'QUERY_STRING'};
}
# Split information into name/value pairs
@pairs = split(/&/, $buffer);
foreach $pair (@pairs) {
   ($name, $value) = split(/=/, $pair);
   $value =~ tr/+/ /;
   $value =~ s/%(..)/pack("C", hex($1))/eg;
   $FORM{$name} = $value;
}
$first_name = $FORM{first_name};
$last_name  = $FORM{last_name};

print "Content-type:text/html\r\n\r\n";
print "<html>";
print "<head>";
print "<title>Hello - Second CGI Program</title>";
print "</head>";
print "<body>";
print "<h2>Hello $first_name $last_name - Second CGI Program</h2>";
print "</body>";
print "</html>";

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Simple FORM Example: GET Method

下面是一个简单的示例，它使用 HTML 表单和提交按钮传递两个值。我们将使用相同的 CGI 脚本 hello_get.cgi 来处理此输入。

Here is a simple example, which passes two values using HTML FORM and submit button. We are going to use the same CGI script hello_get.cgi to handle this input.

<FORM action = "/cgi-bin/hello_get.cgi" method = "GET">
First Name: <input type = "text" name = "first_name">  <br>

Last Name: <input type = "text" name = "last_name">
<input type = "submit" value = "Submit">
</FORM>

这是上面表单代码的实际输出。现在，您可以输入名字和姓氏，然后单击提交按钮以查看结果。

Here is the actual output of the above form coding. Now you can enter First and Last Name and then click submit button to see the result.

Passing Information using POST Method

向 CGI 程序传递信息的更可靠的方法是 POST 方法。这会打包信息的方式与 GET 方法完全相同，但不是在 URL 中在 ? 后面以文本字符串的形式发送，而是作为 HTTP 头的一部分以单独消息的形式发送。Web 服务器会通过标准输入的形式提供此消息给 CGI 脚本。

A more reliable method of passing information to a CGI program is the POST method. This packages the information in exactly the same way as GET methods, but instead of sending it as a text string after a ? in the URL, it sends it as a separate message as a part of HTTP header. Web server provides this message to the CGI script in the form of the standard input.

下面是经过修改的 hello_post.cgi 脚本，用于处理 Web 浏览器给出的输入。此脚本将处理 GET 和 POST 方法。

Below is the modified hello_post.cgi script to handle input given by the web browser. This script will handle GET as well as POST method.

#!/usr/bin/perl

local ($buffer, @pairs, $pair, $name, $value, %FORM);
# Read in text
$ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/;
if ($ENV{'REQUEST_METHOD'} eq "POST") {
   read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
} else {
   $buffer = $ENV{'QUERY_STRING'};
}
# Split information into name/value pairs
@pairs = split(/&/, $buffer);
foreach $pair (@pairs) {
   ($name, $value) = split(/=/, $pair);
   $value =~ tr/+/ /;
   $value =~ s/%(..)/pack("C", hex($1))/eg;
   $FORM{$name} = $value;
}
$first_name = $FORM{first_name};
$last_name  = $FORM{last_name};

print "Content-type:text/html\r\n\r\n";
print "<html>";
print "<head>";
print "<title>Hello - Second CGI Program</title>";
print "</head>";
print "<body>";
print "<h2>Hello $first_name $last_name - Second CGI Program</h2>";
print "</body>";
print "</html>";

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让我们再次举上面的例子，使用 HTML 表单和提交按钮传递两个值。我们将使用 CGI 脚本 hello_post.cgi 来处理此输入。

Let us take again same examle as above, which passes two values using HTML FORM and submit button. We are going to use CGI script hello_post.cgi to handle this input.

<FORM action = "/cgi-bin/hello_post.cgi" method = "POST">
First Name: <input type = "text" name = "first_name">  <br>

Last Name: <input type = "text" name = "last_name">

<input type = "submit" value = "Submit">
</FORM>

这是上面表单代码的实际输出。您可以输入名字和姓氏，然后单击提交按钮以查看结果。

Here is the actual output of the above form coding, You enter First and Last Name and then click submit button to see the result.

Passing Checkbox Data to CGI Program

当需要选择多个选项时，会使用复选框。以下是带两个复选框的表单的 HTML 代码示例。

Checkboxes are used when more than one option is required to be selected. Here is an example HTML code for a form with two checkboxes.

<form action = "/cgi-bin/checkbox.cgi" method = "POST" target = "_blank">
<input type = "checkbox" name = "maths" value = "on"> Maths
<input type = "checkbox" name = "physics" value = "on"> Physics
<input type = "submit" value = "Select Subject">
</form>

这段代码的结果是以下表单−

The result of this code is the following form −

下面是 checkbox.cgi 脚本，用于处理 Web 浏览器给出的单选按钮输入。

Below is checkbox.cgi script to handle input given by web browser for radio button.

#!/usr/bin/perl

local ($buffer, @pairs, $pair, $name, $value, %FORM);
# Read in text
$ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/;
if ($ENV{'REQUEST_METHOD'} eq "POST") {
   read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
} else {
   $buffer = $ENV{'QUERY_STRING'};
}
# Split information into name/value pairs
@pairs = split(/&/, $buffer);
foreach $pair (@pairs) {
   ($name, $value) = split(/=/, $pair);
   $value =~ tr/+/ /;
   $value =~ s/%(..)/pack("C", hex($1))/eg;
   $FORM{$name} = $value;
}
if( $FORM{maths} ) {
   $maths_flag ="ON";
} else {
   $maths_flag ="OFF";
}
if( $FORM{physics} ) {
   $physics_flag ="ON";
} else {
   $physics_flag ="OFF";
}

print "Content-type:text/html\r\n\r\n";
print "<html>";
print "<head>";
print "<title>Checkbox - Third CGI Program</title>";
print "</head>";
print "<body>";
print "<h2> CheckBox Maths is : $maths_flag</h2>";
print "<h2> CheckBox Physics is : $physics_flag</h2>";
print "</body>";
print "</html>";

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Passing Radio Button Data to CGI Program

只有在需要选择一个选项时才使用单选按钮。以下是带两个单选按钮的表单的 HTML 代码示例：

Radio Buttons are used when only one option is required to be selected. Here is an example HTML code for a form with two radio button −

<form action = "/cgi-bin/radiobutton.cgi" method = "POST" target = "_blank">
<input type = "radio" name = "subject" value = "maths"> Maths
<input type = "radio" name = "subject" value = "physics"> Physics
<input type = "submit" value = "Select Subject">
</form>

这段代码的结果是以下表单−

The result of this code is the following form −

下面是 radiobutton.cgi 脚本，用于处理 Web 浏览器给出的单选按钮输入。

Below is radiobutton.cgi script to handle input given by the web browser for radio button.

#!/usr/bin/perl

local ($buffer, @pairs, $pair, $name, $value, %FORM);
# Read in text
$ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/;
if ($ENV{'REQUEST_METHOD'} eq "POST") {
   read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
} else {
   $buffer = $ENV{'QUERY_STRING'};
}
# Split information into name/value pairs
@pairs = split(/&/, $buffer);
foreach $pair (@pairs) {
   ($name, $value) = split(/=/, $pair);
   $value =~ tr/+/ /;
   $value =~ s/%(..)/pack("C", hex($1))/eg;
   $FORM{$name} = $value;
}
$subject = $FORM{subject};

print "Content-type:text/html\r\n\r\n";
print "<html>";
print "<head>";
print "<title>Radio - Fourth CGI Program</title>";
print "</head>";
print "<body>";
print "<h2> Selected Subject is $subject</h2>";
print "</body>";
print "</html>";

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Passing Text Area Data to CGI Program

当需要将多行文本传递给 CGI 程序时，使用文本区域元素。以下是带有一个 TEXTAREA 框的表单的示例 HTML 代码 −

A textarea element is used when multiline text has to be passed to the CGI Program. Here is an example HTML code for a form with a TEXTAREA box −

<form action = "/cgi-bin/textarea.cgi" method = "POST" target = "_blank">
<textarea name = "textcontent" cols = 40 rows = 4>
Type your text here...
</textarea>
<input type = "submit" value = "Submit">
</form>

这段代码的结果是以下表单−

The result of this code is the following form −

以下是 textarea.cgi 用于处理 web 浏览器给出的输入的脚本。

Below is the textarea.cgi script to handle input given by the web browser.

#!/usr/bin/perl

local ($buffer, @pairs, $pair, $name, $value, %FORM);
# Read in text
$ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/;
if ($ENV{'REQUEST_METHOD'} eq "POST") {
   read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
} else {
   $buffer = $ENV{'QUERY_STRING'};
}
# Split information into name/value pairs
@pairs = split(/&/, $buffer);
foreach $pair (@pairs) {
   ($name, $value) = split(/=/, $pair);
   $value =~ tr/+/ /;
   $value =~ s/%(..)/pack("C", hex($1))/eg;
   $FORM{$name} = $value;
}
$text_content = $FORM{textcontent};

print "Content-type:text/html\r\n\r\n";
print "<html>";
print "<head>";
print "<title>Text Area - Fifth CGI Program</title>";
print "</head>";
print "<body>";
print "<h2> Entered Text Content is $text_content</h2>";
print "</body>";
print "</html>";

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Passing Drop Down Box Data to CGI Program

当我们有许多可用的选项但只选择一两个选项时，使用下拉框。以下是带有一个下拉框的表单的示例 HTML 代码

A drop down box is used when we have many options available but only one or two will be selected. Here is example HTML code for a form with one drop down box

<form action = "/cgi-bin/dropdown.cgi" method = "POST" target = "_blank">
<select name = "dropdown">
<option value = "Maths" selected>Maths</option>
<option value = "Physics">Physics</option>
</select>
<input type = "submit" value = "Submit">
</form>

这段代码的结果是以下表单−

The result of this code is the following form −

以下是 dropdown.cgi 用于处理 web 浏览器给出的输入的脚本。

Below is the dropdown.cgi script to handle input given by web browser.

#!/usr/bin/perl

local ($buffer, @pairs, $pair, $name, $value, %FORM);
# Read in text
$ENV{'REQUEST_METHOD'} =~ tr/a-z/A-Z/;
if ($ENV{'REQUEST_METHOD'} eq "POST") {
   read(STDIN, $buffer, $ENV{'CONTENT_LENGTH'});
} else {
   $buffer = $ENV{'QUERY_STRING'};
}
# Split information into name/value pairs
@pairs = split(/&/, $buffer);
foreach $pair (@pairs) {
   ($name, $value) = split(/=/, $pair);
   $value =~ tr/+/ /;
   $value =~ s/%(..)/pack("C", hex($1))/eg;
   $FORM{$name} = $value;
}
$subject = $FORM{dropdown};

print "Content-type:text/html\r\n\r\n";
print "<html>";
print "<head>";
print "<title>Dropdown Box - Sixth CGI Program</title>";
print "</head>";
print "<body>";
print "<h2> Selected Subject is $subject</h2>";
print "</body>";
print "</html>";

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Using Cookies in CGI

HTTP 协议是一个无状态协议。但是，对于商业网站而言，需要在不同页面之间维护会话信息。例如，一个用户注册在跨越许多页面的事务之后结束。但如何在所有网页中维护用户的会话信息？

HTTP protocol is a stateless protocol. But for a commercial website it is required to maintain session information among different pages. For example one user registration ends after transactions which spans through many pages. But how to maintain user’s session information across all the web pages?

在许多情况下，使用 cookie 是记忆和跟踪偏好、购买、佣金和其他信息最有效的方法，而这些信息对于提升访问者体验或网站统计至关重要。

In many situations, using cookies is the most efficient method of remembering and tracking preferences, purchases, commissions, and other information required for better visitor experience or site statistics.

How It Works

您的服务器会以 Cookie 的形式向访客的浏览器发送一些数据。浏览器可能会接受 Cookie。如果接受，它将作为纯文本记录存储在访客硬盘上。现在，当访客到达您站点上的另一个页面时，可以检索 Cookie。检索后，您的服务器知道/记住存储的内容。

Your server sends some data to the visitor’s browser in the form of a cookie. The browser may accept the cookie. If it does, it is stored as a plain text record on the visitor’s hard drive. Now, when the visitor arrives at another page on your site, the cookie is available for retrieval. Once retrieved, your server knows/remembers what was stored.

Cookie 是纯文本数据记录，包含 5 个可变长度字段：

Cookies are a plain text data record of 5 variable-length fields −

  1. Expires − The date the cookie will expire. If this is blank, the cookie will expire when the visitor quits the browser.

  2. Domain − The domain name of your site.

  3. Path − The path to the directory or web page that set the cookie. This may be blank if you want to retrieve the cookie from any directory or page.

  4. Secure − If this field contains the word "secure" then the cookie may only be retrieved with a secure server. If this field is blank, no such restriction exists.

  5. Name = Value − Cookies are set and retrviewed in the form of key and value pairs.

Setting up Cookies

将 Cookie 发送到浏览器非常容易。这些 Cookie 将与 HTTP 标头一起发送。假设你想要将 UserID 和 Password 设置为 Cookie。因此，将按如下进行 −

It is very easy to send cookies to browser. These cookies will be sent along with the HTTP Header. Assuming you want to set UserID and Password as cookies. So it will be done as follows −

#!/usr/bin/perl

print "Set-Cookie:UserID = XYZ;\n";
print "Set-Cookie:Password = XYZ123;\n";
print "Set-Cookie:Expires = Tuesday, 31-Dec-2007 23:12:40 GMT";\n";
print "Set-Cookie:Domain = www.tutorialspoint.com;\n";
print "Set-Cookie:Path = /perl;\n";
print "Content-type:text/html\r\n\r\n";
...........Rest of the HTML Content goes here....

这里我们使用 Set-Cookie HTTP 标头来设置 Cookie。设置 Expires、Domain 和 Path 等 Cookie 属性是可选的。务必要注意，在发送魔术行 "Content-type:text/html\r\n\r\n 之前设置 Cookie。

Here we used Set-Cookie HTTP header to set cookies. It is optional to set cookies attributes like Expires, Domain, and Path. It is important to note that cookies are set before sending magic line "Content-type:text/html\r\n\r\n.

Retrieving Cookies

非常容易检索所有设置的 Cookie。Cookie 存储在 CGI 环境变量 HTTP_COOKIE 中，它们将具有以下形式。

It is very easy to retrieve all the set cookies. Cookies are stored in CGI environment variable HTTP_COOKIE and they will have following form.

key1 = value1;key2 = value2;key3 = value3....

以下是有关如何检索 cookie 的示例。

Here is an example of how to retrieve cookies.

#!/usr/bin/perl
$rcvd_cookies = $ENV{'HTTP_COOKIE'};
@cookies = split /;/, $rcvd_cookies;
foreach $cookie ( @cookies ) {
   ($key, $val) = split(/=/, $cookie); # splits on the first =.
   $key =~ s/^\s+//;
   $val =~ s/^\s+//;
   $key =~ s/\s+$//;
   $val =~ s/\s+$//;
   if( $key eq "UserID" ) {
      $user_id = $val;
   } elsif($key eq "Password") {
      $password = $val;
   }
}
print "User ID  = $user_id\n";
print "Password = $password\n";

在调用读取 cookie 脚本之前设置好 cookie，将产生以下结果，如上所述。

This will produce the following result, provided above cookies have been set before calling retrieval cookies script.

User ID = XYZ
Password = XYZ123

CGI Modules and Libraries

您会在互联网上找到许多内置模块，这些模块为您提供了可在 CGI 程序中直接使用的功能。以下是最重要的。

You will find many built-in modules over the internet which provides you direct functions to use in your CGI program. Following are the important once.

  1. CGI Module

  2. Berkeley cgi-lib.pl