Comparison of CGI libraries in C

This is a work-in-progress comparing the available libraries for dealing with CGI (Common Gateway Interface) in C. After having looked at the available libraries shown below for dealing with CGI in C, I actually decided to write my own. At the moment it is not ready for public release. As part of the process of preparing it for general release, I've made the following comparison.

Libraries

Library name (host) (Links open in a new window)	Last update	Author	Last version	Licence
Lightweight CGI Library (www.infodrom.org)	2009-02-08	Martin Schulze	0.7	GNU GPL	Download
cgic (www.boutell.com)	2008	Thomas Boutrell	2.05	Advertising (see site for details)	Download
libcgic (www.pavluk.org)	2008	Vladimir V. Pavluk
CGL (www.harding.motd.ca)	2005-08-18	Carson Harding	1.2	BSD-like	Download
cgi-util (www.newbreedsoftware.com)	2005	Bill Kendrick, Mike Simons	2.2.1	GNU Library GPL	Download
CGI-LIB (www.joeldare.com)	2004	Noel V Aguilar, Joel Dare
cgihtml (www.eekim.com)	2001-05-25	Eric E. Kim	1.69	Unspecified	Download
A CGI Library for C (sourceforge.net)	1999	William L. Chatfield	1.0	GNU GPL or GNU Library GPL	Download

Features

Basics

	C version	Documentation	Automated tests
Lightweight CGI Library	`GNU C`	`yes (man files)`	?
cgic	`ANSI`	`yes (web page)`	?
libcgic	Unknown	×	?
CGL	Unknown	`yes (doc/cgl.txt)`	?
cgi-util	Unknown	`yes (README.txt)`	?
CGI-LIB	Unknown	?	?
cgihtml	Unknown	○	?
A CGI Library for C	Unknown	×	?

HTTP headers

	Set content type	Set encoding	Set status	Set error message	Add arbitrary HTTP headers	Print header
Lightweight CGI Library	`cgiSetType`	×	×	×	`cgiSetHeader`	`cgiHeader`
cgic	`cgiHeaderContentType`	×	`cgiHeaderStatus`	`cgiHeaderStatus`	×	×
libcgic	?	?	?	?	?	?
CGL	`cgl_content_header`	×	`cgl_status_header`	`cgl_status_header`	×	`cgl_html_header`
cgi-util	×	×	×	×	×	×
CGI-LIB	?	?	?	?	?	?
cgihtml	`mime_header`	×	`status`	`status`	×	`http_header`
A CGI Library for C	×	×	×	×	×	×

Form parsing

	process query string	application/x-url-formencoded	multipart/form-data (file upload)	Multiple values for one key	uri escape	uri unescape
Lightweight CGI Library	○	○	○	`separated by \n`	×	×
cgic	○	○	○	`cgiFormStringMultiple`	×	×
libcgic	?	?	?	?	?	?
CGL	○	○	×	`cgl_getvalues`	`cgl_urlencode`	`cgl_urldecode`
cgi-util	○	○	○	×	×	`unescape_url`
CGI-LIB	?	?	?	?	?	?
cgihtml	○	○	○	`cgi_name_multi`	×	`unescape_url`
A CGI Library for C	○	○	○	×	×	×

Cookies

	Read cookies	Set cookies	Create cookie time strings	Delete cookies
Lightweight CGI Library	○	×	×	×
cgic	○	○	○	×
libcgic	?	?	?	?
CGL	○	○	`cgl_cookietime`	×
cgi-util	`cgi_getcookie`	×	×	×
CGI-LIB	?	?	?	?
cgihtml	○	○	×	×
A CGI Library for C	×	×	×	×

Extras

	html generation	compression	save environment	Redirects
Lightweight CGI Library	×	×	×	`cgiRedirect`
cgic	×	×	`cgiWriteEnvironment`	`cgiHeaderLocation`
libcgic	?	?	?	?
CGL	○	×	`cgl_dumpenv`	×
cgi-util	×	×	×	×
CGI-LIB	?	?	?	?
cgihtml	○	×	`print_cgi_env`	×
A CGI Library for C	×	×	×	×

Key:

×: Does not have this feature
?: Unknown or not tested
◯: Has this feature

Reviews

"Lightweight CGI Library" by Martin Schulze

Appears to be the author's personal hack more than anything else. The use of C string functions in parsing multipart/form-data is likely to cause problems in the case of binary file uploads with bytes equal to zero.

The web page for this library claims that it supports writing cookies, but I could not see where this was implemented.

"cgic" by Thomas Boutrell

The "advertising" licence is a nuisance, and limits the library's usefulness. For some reason, this library provides a main function, and insists that the user uses something called cgiMain instead. The first thing the library does is to read every possible environment variable, but most of these it goes on to completely ignore. The library is missing some obvious features such as the ability to set the page's encoding.

"CGL" by Carson Harding

A lot of this code looks useful, but it barely seems to be robust.

Careless in the way that it relies on printf for functions like setting the HTTP headers, so there is no distinction between creating the flow of output and setting the headers. This kind of behaviour tends to make debugging difficult. The library is also missing the feature of multipart form handling (file uploads).

The extensive use of hash tables to store form name and value pairs looks a bit excessive considering the number of these things in even a fairly large HTML form.

The library also contains a facility to print headers as if it was a web server rather than a CGI library.

"cgi-util" by Bill Kendrick, Mike Simons

This library is not clearly documented, and seems to be somewhat incomplete. For example, it provides nothing to deal with HTTP headers or cookies. On the bright side, it contains a lot of error status checking. It also contains odd-bod functions like an email address validation routine.

"cgihtml" by Eric E. Kim

This library is no longer updated by its author. Its internals refer to ancient bugs of Netscape Navigator and use fairly cludgy methods to do things like detect whether the browser can accept images.

"A CGI Library for C" by William L. Chatfield

This library has no documentation. Scanning the code, it looks like the main ability is to parse HTML form data. However, it does not cope with multiple values with the same name. It does not seem to have any output parts.