The WOPI CGI falcon module front-end, called cgi_fm is a module that can be injected in a script executed through the falcon command line interpreter, causing the WOPI interface to be made available in the calling script.
The script must be made executable and the web server must be configured so that it can ask the system to execute a standard falcon interpreter to run the script.
On POSIX systems, this usually means adding a sh-bang directive on the very first line of the main script (the one that is directly loaded by the server), like the following:
#!/usr/bin/falcon -pcgi
Usually, web servers running on MS-Windows operating systems can be configured so that target scripts can be passed to a certain executable interpreter, together with other parameters on the command line through which the program is invoked.
The main CGI script may also use the load falcon directive to activate the CGI module, but this would make it impossible to be used as-is under other WOPI front-ends.
Note: The Falcon command line interpreter sends error reports on the process error stream. This makes errors invisible on the remote browser side, but web servers are usually copying the text sent on the standard error of CGI programs to a log facility. Fatal errors caused by scripts using this front-end shall be logged directly by the web server. Future versions of Falcon command line program may include options to control this behavior.
Note: Be sure to read the Isomorphism of CGI based sites. documentation about specificities of the CGI model.
The CGI front-end reads the following attributes from the main module:
Other than that, you have to activate the ability to execute CGI programs from within the web server you're currently using. Check the documentation of the web server for further information.