CGI & Perl Articles

Synopsis: The Common Gateway Interface (CGI) is a standard for interfacing external programs with the Web servers. In absence of appropriate security measures, CGI scripts can present a variety of security problems to their host. Solutions are suggested by Pankaj Kamthan to minimize these problems, and even eliminate them in certain cases.

Techniques: CGI, SSI, privileges, security, NOBODY, wrappers, CGIWrap, SBOX, suEXEC, Apache, tainting, Shell, back ticks, pre-built CGI scripts

Synopsis: In this article Jason Nugent describes a counter that can be run as a Server Side Include. Essentially that means writing a Perl script that will run each time the page is loaded and its output will contain a line of text indicating how many people have seen the page.

Techniques: Counter, Perl, Server Side Include, SSI

Synopsis: The Common Gateway Interface (CGI) is a standard for interfacing external programs with the Web servers. Under testing conditions, such as computationally-intensive tasks or large number of concurrent users, CGI scripts can degrade in performance. Reasons for this behaviour are pointed out and solutions are suggested by Pankaj Kamthan.

Techniques: CGI Performance, CGI Optimization, Perl, Tools, I/O Buffering, Reverse DNS Lookups, Non-Parsed Headers, NPH, Client-Side Processing, State Persistence Using Cookies, Coprocessing, mod_perl

Synopsis: The Common Gateway Interface (CGI) is a standard for external gateway programs to interface with HTTP servers. CGI libraries simplify the task of writing CGI scripts. The use of one widely used CGI library, CGI.pm, is discussed in detail by Pankaj Kamthan.

Techniques: CGI Libraries, cgi-lib.pl, CGI Lite, CGI :: * Modules, CGI.pm

Synopsis: Server-side includes (SSI's) extend and introduce implicit dynamism in HTML documents, and can be a useful alternative to CGI's in certain cases. Use of SSI's, and their extensions in the Apache WWW server, XSSI's, are described. Applications SSI's and XSSI's are given. Written by Pankaj Kamthan

Techniques: Server-Side Includes, SSI, Extended Server-Side Includes, XSSI, Editing, Environment Variables, Directives, config, echo, exec, flastmod, fsize, include, Configuration, Debugging, printenv, set, if, elif, else, endif, Variable Substitution, XBitHack, Applications of XSSI's, Concerns, Performance, Security

Synopsis: Ha Quach explains how to use the Perl crypt() function to create random and recursive crypted passwords for both Unix and Win32 systems

Techniques: crypt(), Unix, Win32, Perl, salt keys, passwords, cryption, rand()

Synopsis: Pankaj Kamthan presents two solutions - one on the client-side, and the other on the server-side - to the problem of including the date of last modification of an HTML document. Limitations of these approaches are also pointed out.

Techniques: Date & Time stampimg, lastModified, SSI, Server Side Includes, *.shtml, #echo, #include, Client Side JavaScript, JavaScript source files, Perl, finding and renaming files

Synopsis: Wing Lu shows how to delete files using Perl, and provides a simple trick to eanble you to recover files from a trash directory.

Techniques: Perl, files, create, delete, unlink, link, rename, rmdir, recovering trashed files

Synopsis: Jason Nugent shows how to combine a form with a Perl script to enable visitors to leave their email addresses in a file on your server, which can then be used with yet another Perl program to send out a regular newsletter

Techniques: Perl, CGI-BIN, Forms, email, newsletters, writing and reading files on the server

Synopsis: This article written by Jason Nugent will discuss the mechanisms most often used in Perl scripts to store data out to the filesystem so it can be used again at a later time. Once your data is in a file on the server, other programs may access it, you can manipulate it, graph it, or do just about anything you want with it.

Techniques: reading and writing files, file handle, open(), read, write, append, flock(), locking files, die, $!, print, close

Synopsis: Jason Nugent continues the CGI/Perl series of articles - this issue dicusses Server Side Includes and CGI Security

Techniques: SSI, Server Side Includes, config, include, echo, fsize, flastmod, exec, errmsg, sizefmt, LAST_MODIFIED, DOCUMENT_NAME, DOCUMENT_URI, DATE_LOCAL, SERVER_NAME, cgi, cmd, Apache, .shtml, .shtm, .sht, security, HTTP_REFERER

Synopsis: Written by Jason Nugent. In this article, the detailed steps required to extract the information that is sent to your CGI program is described. The article is fairly Perl intensive, but hopefully the examples will make it easy enough to follow.

Techniques: CGI, GET, POST, Perl variables, scalars, arrays, Hashes, Associative Arrays, $ENV, QUERY_STRING, REQUEST_METHOD, CONTENT_LENGTH, Regular Expressions, form parser script

Synopsis: Jason Nugent continues with the new series of articles on CGI scripting.

Techniques: form, action, method, get, post, perl, encoding, print

Synopsis: Jason Nugent returns this time with the first in a new series of articles on CGI (Common Gateway Interface) Scripts. This article introduces CGI, the benefits, the drawbacks, and the language of choice: Perl.

Techniques: CGI, Perl