The question was specifically about CGI. As part of the CGI specification, you'll see that some environmental variables are specifically set for every request. (including the two I mentioned originally)

It's always possible that some of the other more-than-just-CGI implementations (FastCGI, mod_perl, etc), behave differently, as well as software that doesn't correctly implement the CGI specifications.

However, for my install of mod_perl (using Apache::Registry, Apache 1.3, Mac OS X), in using the following simple script:

#!/usr/bin/perl --

use Data::Dumper;
print "Content-Type: text/plain\n\n",
      Dumper \%ENV;

[download]

I get after censoring out the host name:

$VAR1 = {
          'SCRIPT_NAME' => '/cgi/test-cgi',
          'SERVER_NAME' => '[censored]',
          'SERVER_ADMIN' => '[no address given]',
          'PERL_SEND_HEADER' => 'On',
          'REQUEST_METHOD' => 'GET',
          'SCRIPT_URI' => 'http://[censored]/cgi/test-cgi',
          'SCRIPT_FILENAME' => '/Library/Webserver/Mod_Perl-Executable
+s/test-cgi',
          'SERVER_SOFTWARE' => 'Apache/1.3.33 (Darwin) mod_perl/1.29',
          'QUERY_STRING' => '',
          'REMOTE_PORT' => '53739',
          'SERVER_SIGNATURE' => '<ADDRESS>Apache/1.3.33 Server at [cen
+sored] Port 80</ADDRESS>
',
          'SERVER_PORT' => '80',
          'REMOTE_ADDR' => '127.0.0.1',
          'SERVER_PROTOCOL' => 'HTTP/1.0',
          'PATH' => '/bin:/sbin:/usr/bin:/usr/sbin:/usr/libexec:/Syste
+m/Library/CoreServices',
          'REQUEST_URI' => '/cgi/test-cgi',
          'GATEWAY_INTERFACE' => 'CGI-Perl/1.1',
          'SCRIPT_URL' => '/cgi/test-cgi',
          'SERVER_ADDR' => '127.0.0.1',
          'DOCUMENT_ROOT' => '/Library/WebServer/Documents',
          'MOD_PERL' => 'mod_perl/1.29'
        };

[download]

You'll notice that 'GATEWAY_INTERFACE' is still defined, and indicates that it's not a standard CGI.

Using Apache::PerlRun is the almost identical:

$VAR1 = {
          'SCRIPT_NAME' => '/perl/test-cgi',
          'SERVER_NAME' => '[censored]',
          'SERVER_ADMIN' => '[no address given]',
          'PERL_SEND_HEADER' => 'On',
          'REQUEST_METHOD' => 'GET',
          'SCRIPT_URI' => 'http://[censored]/perl/test-cgi',
          'SCRIPT_FILENAME' => '/Library/Webserver/Mod_Perl-Executable
+s/test-cgi',
          'SERVER_SOFTWARE' => 'Apache/1.3.33 (Darwin) mod_perl/1.29',
          'QUERY_STRING' => '',
          'REMOTE_PORT' => '53741',
          'SERVER_SIGNATURE' => '<ADDRESS>Apache/1.3.33 Server at [cen
+sored] Port 80</ADDRESS>
',
          'SERVER_PORT' => '80',
          'REMOTE_ADDR' => '127.0.0.1',
          'SERVER_PROTOCOL' => 'HTTP/1.0',
          'PATH' => '/bin:/sbin:/usr/bin:/usr/sbin:/usr/libexec:/Syste
+m/Library/CoreServices',
          'REQUEST_URI' => '/perl/test-cgi',
          'GATEWAY_INTERFACE' => 'CGI-Perl/1.1',
          'SCRIPT_URL' => '/perl/test-cgi',
          'SERVER_ADDR' => '127.0.0.1',
          'DOCUMENT_ROOT' => '/Library/WebServer/Documents',
          'MOD_PERL' => 'mod_perl/1.29'
        };

[download]

In reply to Re^4: Telling if your script is running from web page or CLI by jhourcle
in thread Telling if your script is running from web page or CLI by dizzyg

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