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“main” (Installation and Administration) — 2004/6/25 — 13:29 — page 543 — #569

The Apache Web Server

22.9.1 Server Side Includes: SSI

Server-side includes are directives that are embedded in special

comments and executed by Apache. The result is embedded

in the output. For example, the current date can be printed with

. The # at the end of the opening

comment mark <!-- shows Apache that this is an SSI directive and not a

simple comment.

SSIs can be activated in several ways. The easiest approach is to search all

executable ﬁles for SSIs. Another approach is to specify certain ﬁle types to

search for SSIs. Both settings are explained in Section 22.7.2 on page 540.

22.9.2 Common Gateway Interface: CGI

CGI is the abbreviation for common gateway interface. With CGI, the server

does not simply deliver a static HTML page, but executes a program that

generates the page. This enables the generation of pages representing the

result of a calculation, such as the result of the search in a database. By

means of arguments passed to the executed program, the program can re-

turn an individual response page for every request.

The main advantage of CGI is that this technology is quite simple. The pro-

gram merely must exist in a speciﬁc directory to be executed by the web

server just like a command-line program. The server sends the program

output on the standard output channel (stdout) to the client.

22.9.3 GET and POST

Input parameters can be passed to the server with GET or POST. Depend-

ing on which method is used, the server passes the parameters to the script

in various ways. With POST, the server passes the parameters to the pro-

gram on the standard input channel (stdin). The program would receive

its input in the same way when started from a console.

With GET, the server uses the environment variable QUERY_STRING to pass

the parameters to the program. An environment variable is a variable made

available globally by the system (such as the variable PATH, which contains

a list of paths the system searches for executable commands when the user

enters a command).

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SUSE LINUX Enterprise Server