CGI

From DreamHost

Common Gateway Interface ('CGI) is an important World Wide Web technology that enables a client web browser to request data from a program executed on the Web server. CGI specifies a standard for passing request data between a web server and the program used to service that request. CGI are often preferred by web developers because of their speed and their minimal resource requirements. A CGI on DreamHost could be a java .jar, a shell script .sh, a perl .pl, a ruby .rb, python, etc. In fact, the PHP interpreter preferred and installed by default on DreamHost is a CGI version. /dh/cgi-system/php5.cgi

To install a cgi script on dreamhost the following seems to work:

• create a directory where you want to place the script. For example you could create a cgi-bin directory in your domain (yourdomain/cgi-bin).
• edit or create the .htaccess file in that directory and add Options +ExecCGI (this is not necessary as we automatically set this for all domains and it works for any folder within domains. --Dallas 12:10, 7 April 2008 (PDT))
• place the scripts in that directory
• because dreamhost runs suexec (which means that the scripts will be run with you as user and not the apache www user) you need to also do the following:
  • chmod -R 755 cgi-bin (See Suexec)
  • try chmod u+rx on your security sensitive scripts to allow your user execute perms
  • make sure that you are listed as a user
  • make sure that your default group is listed as group (else do a chgrp -R pg****** cgi-bin)
  • if you set up permissions incorrectly, you'll probably get "500 Internal Server Error"
• take care of the script file name extension. The server understands several extensions, like ".pl", but if you get source code of your script instead of result of its execution, try to use universal extension ".cgi" (or ".fcgi" for FastCGI)

Contents 1 CGI Examples Scripts 1.1 CGI Shell Script 1.2 PerlCGI Example 1.3 Suexec 2 FAQs 3 External Links 4 See Also

CGI Examples Scripts

CGI Shell Script

Create this file as test-cgi.cgi in your /cgi-bin/ directory with permissions set as chmod u+rx or the least secure, 750.

#!/bin/sh

# disable filename globbing
set -f

echo "Content-type: text/plain; charset=iso-8859-1"
echo

echo CGI/1.0 test script report:
echo

echo argc is $#. argv is "$*".
echo

echo SERVER_SOFTWARE = $SERVER_SOFTWARE
echo SERVER_NAME = $SERVER_NAME
echo GATEWAY_INTERFACE = $GATEWAY_INTERFACE
echo SERVER_PROTOCOL = $SERVER_PROTOCOL
echo SERVER_PORT = $SERVER_PORT
echo REQUEST_METHOD = $REQUEST_METHOD
echo HTTP_ACCEPT = "$HTTP_ACCEPT"
echo PATH_INFO = "$PATH_INFO"
echo PATH_TRANSLATED = "$PATH_TRANSLATED"
echo SCRIPT_NAME = "$SCRIPT_NAME"
echo QUERY_STRING = "$QUERY_STRING"
echo REMOTE_HOST = $REMOTE_HOST
echo REMOTE_ADDR = $REMOTE_ADDR
echo REMOTE_USER = $REMOTE_USER
echo AUTH_TYPE = $AUTH_TYPE
echo CONTENT_TYPE = $CONTENT_TYPE
echo CONTENT_LENGTH = $CONTENT_LENGTH

PerlCGI Example

#!/usr/bin/perl
##
##  printenv -- demo CGI program which just prints its environment
##

print "Content-type: text/plain; charset=iso-8859-1\n\n";
foreach $var (sort(keys(%ENV))) {
    $val = $ENV{$var};
    $val =~ s|\n|\\n|g;
    $val =~ s|"|\\"|g;
    print "${var}=\"${val}\"\n";
}

Suexec

The suEXEC feature provides DreamHost users the ability to run CGI programs that are different from the calling web server. Normally, when a CGI executes, it runs as the same user who is running the web server.

Suexec has very strict permission checking, and any failure in that checking will result in your CGI programs failing with

Premature end of script headers.

Also note that suexec wips out all environment variables that don't start with HTTP_. So in .htaccess:

SetEnv FOO "will not work"
SetEnv HTTP_BAR "will work"

This is a bit hacky but it seems to be the only workaround.

FAQs

Question: Do I have to place a CGI script in the cgi-bin directory?

Answer: No, well... maybe you should try it out first. For example, the blosxom.com perl based CGI works fine in the domain home folder renamed index.cgi

External Links

• Apache Tutorial: Dynamic Content with CGI
• suEXEC Information
• Writing a CGI Program
• cgi Apache Module mod_cgi

See Also

• PHP FastCGI
• suexec

(Old KB Article on CGI)