Apache: The Definitive Guide, 3rd Edition

Environment Variables

Every request from a browser brings a raft of information with it to Apache, which reappears as environment variables. It can be very useful to have a subroutine like this:

sub print_env
    {
    foreach my $e (keys %ENV)
        {
        print "$e=$ENV{$e}\n";
        }
    }

If you call it at the top of a web page, you see something like this on your browser screen:

SERVER_SOFTWARE = Apache/1.3.9 (Unix) mod_perl/1.22
GATEWAY_INTERFACE = CGI/1.1
DOCUMENT_ROOT = /usr/www/APACHE3/MedicPlanet/site.medic/htdocs
REMOTE_ADDR = 192.168.123.1
SERVER_PROTOCOL = HTTP/1.1
SERVER_SIGNATURE = 
REQUEST_METHOD = GET
QUERY_STRING = 
HTTP_USER_AGENT = Mozilla/4.0 (compatible; MSIE 4.01; Windows 95)
PATH = /sbin:/bin:/usr/sbin:/usr/bin:/usr/games:/usr/local/sbin:/usr/local/bin:
/usr/X11R6/bin:/root/bin
HTTP_ACCEPT = image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, 
application/vnd.ms-excel, application/msword, application/vnd.ms-powerpoint, */*
HTTP_CONNECTION = Keep-Alive
REMOTE_PORT = 1104
SERVER_ADDR = 192.168.123.5
HTTP_ACCEPT_LANGUAGE = en-gb
SCRIPT_NAME = 
HTTP_ACCEPT_ENCODING = gzip, deflate
SCRIPT_FILENAME = /usr/www/APACHE3/MedicPlanet/cgi-bin/MP_home
SERVER_NAME = www.Medic-Planet-here.com
PATH_INFO = /
REQUEST_URI = /
HTTP_COOKIE = Apache=192.168.123.1.1811957344309436; Medic-Planet=8335562231
SERVER_PORT = 80
HTTP_HOST = www.medic-planet-here.com
PATH_TRANSLATED = /usr/www/APACHE3/MedicPlanet/cgi-bin/MP_home/
SERVER_ADMIN = [no address given

All of these environment variables are available to your ...