Perl coding download#

The browser uses this value to report the estimated download time for a file.ДЄll the CGI program will have access to the following environment variables. The length, in bytes, of the data being returned. The date of last modification of the file. You can use this filed to redirect a request to any other location. The URL that should be returned instead of the URL requested. A valid date string should be in the format 12:00:00 GMT. This should be used by the browser to decide when a page needs to be refreshed. The date when the information becomes invalid. Sr.No.ДЄ MIME string defining the format of the content being returned. There are few other important HTTP headers, which you will use frequently in your CGI Programming. All the HTTP header will be in the following form в€’ДЇor Example в€’ Content-type: text/html The very first line Content-type:text/html is a part of HTTP header, which is sent to the browser so that browser can understand the incoming content from server side. This script can interact with any other exertnal system also to exchange information such as a database, web services, or any other complex interfaces. Now you must have undertood basic concept of CGI and you can write many complicated CGI programs using Perl. This line is sent back to the browser and specifies the content type to be displayed on the browser screen. There is one important and extra feature available which is first line to be printed Content-type:text/html . This hello.cgi script is a simple Perl script which is writing its output on STDOUT file, i.e., screen.

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 в€’ Hello Word! This is my first CGI program Print 'Hello Word! This is my first CGI program' Before running your CGI program, make sure you have change mode of file using chmod 755 hello.cgi UNIX command. This file has been kept in /cgi-bin/ directory and it has the following content. Here is a simple link which is linked to a CGI script called hello.cgi. By convention Perl CGI files will have extention as. This directory is called CGI directory and by convention it is named as /cgi-bin. All the CGI programs to be executed by the web server are kept in a pre-configured directory. CGI Architecture Diagram Web Server Support and ConfigurationД«efore you proceed with CGI Programming, make sure that your Web Server supports CGI functionality and it is configured to handle CGI programs. These CGI programs can be a PERL Script, Shell Script, C or C++ program, etc. 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. 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. Web browser takes response from web server and displays either the received file content or an error message in case file is not found. 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. Web Server will check the URL and will look for the filename requested. Your browser contacts web server using HTTP protocol and demands for the URL, i.e., web page filename.

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. The current version is CGI/1.1 and CGI/1.2 is under progress. The Common Gateway Interface, or CGI, is a standard for external gateway programs to interface with information servers such as HTTP servers. The CGI specs are currently maintained by the NCSA and NCSA defines CGI is as follows в€’ 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.

Perl coding