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CGI Programming on the World Wide Web

CGI Programming on the World Wide Web

By Shishir Gundavaram
1st Edition March 1996

This book is out of print, but it has been made available online through the O'Reilly Open Books Project.

Previous Chapter 2
Input to the Common Gateway Interface

2.8 Examining Environment Variables

What would the chapter be without a program that displays some of the commonly used environment variables? Here it is:

%list = ('SERVER_SOFTWARE',   'The server software is: ',
         'SERVER_NAME',       'The server hostname, DNS alias, or IP address is: ',
         'GATEWAY_INTERFACE', 'The CGI specification revision is: ',   
         'SERVER_PROTOCOL',   'The name and revision of info protocol is: ',
         'SERVER_PORT',       'The port number for the server is: ',
         'REQUEST_METHOD',    'The info request method is: ',
         'PATH_INFO',         'The extra path info is: ',
         'PATH_TRANSLATED',   'The translated PATH_INFO is: ',
         'DOCUMENT_ROOT',     'The server document root directory is: ',
         'SCRIPT_NAME',       'The script name is: ',
         'QUERY_STRING',      'The query string is (FORM GET): ',
         'REMOTE_HOST',       'The hostname making the request is: ',
         'REMOTE_ADDR',       'The IP address of the remote host is: ',
         'AUTH_TYPE',         'The authentication method is: ',
         'REMOTE_USER',       'The authenticated user is: ',
         'REMOTE_IDENT',      'The remote user is (RFC 931): ',
         'CONTENT_TYPE',      'The content type of the data is (POST, PUT): ',
         'CONTENT_LENGTH',    'The length of the content is: ',
         'HTTP_ACCEPT',       'The MIME types that the client will accept are: ',
         'HTTP_USER_AGENT',   'The browser of the client is: ',
         'HTTP_REFERER',      'The URL of the referer is: ');
print "Content-type: text/html","\n\n";
print "<HTML>", "\n";
print  "<HEAD><TITLE>List of Environment Variables</TITLE></HEAD>", "\n";
print "<BODY>", "\n";
print "<H1>", "CGI Environment Variables", "</H1>", "<HR>", "\n";
while ( ($env_var, $info) = each %list ) {
      print $info, "<B>", $ENV{$env_var}, "</B>", "<BR>","\n";
print "<HR>", "\n";
print "</BODY>", "</HTML>", "\n";
exit (0);

The associative array contains each environment variable and its description. The while loop iterates through the array one variable at a time with the each command. Figure 2.3 shows what the output will look in a browser window.

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