sitehost: manual: 11 - CGI ]
Chapter Eleven - CGI Scripts
CGI stands for "Common Gateway Interface," a fancy name meaning computer programs running on the web server that can be invoked from a www page at the browser. The "bin" part alludes to the binary executables that result from compiled or assembled programs. It is a bit misleading because cgi's can also be Unix shell scripts or interpreted languages like Perl. CGI scripts need to be saved in ASCII format and uploaded to your server's cgi-bin in ASCII or text format. This is very important.
We do not provide Technical Support for CGI scripts. So if you are not already familiar with CGI scripting, you may want to read a book on the subject or find places on the Internet with CGI scripting information. There are many good resources for CGI scripts found on the web. The scripts at Matt's Script Archive found at http://www.worldwidemart.com/scripts/ are very good. You'll find many scripts free of charge and with detailed configuration information. Another excellent resource is The CGI Resource Index found at http://www.cgi-resources.com/ -- if you are not an expert, look for scripts that are very well documented and come with step-by-step instructions.
Put your cgi-bin scripts in the www subdirectory named "cgi-bin".
Here are your paths to the common server resources that CGI scripts often require:
The following is a simple explanation of file permissions in Unix. To list the access permissions of a file or directory, telnet to your server, then:
to change the directory until you are either in the directory above the file you are interested in, or above the directory you are checking.
Type: ls -l filename
and you will see what the current permission settings are for that file, along with a bunch of other stuff.
Examples of using chmod:
To change permissions for a file named filename.cgi, you need to chmod the file (change mode). For example, when you type this:
chmod u=rwx,g=rx,o=rx filename.cgi
by typing this you have given:
read, execute, and write access to the user (that's you)
read and execute access to the group and;
read and execute access to others
Some scripts will tell you to chmod 775 (for example). Doing the above is the same thing as typing chmod 775. You can use either method with our Unix servers. Let me explain:
When using the numeric system, the code for permissions is as follows:
r = 4 w = 2 x = 1 rwx = 7
The first 7 of our chmod775 tells Unix to change the user's permissions to rxw (because r=4 + w=2 + x=1 adds up to 7. The second 7 applies to the group, and the last number 5, refers to others (4+1=5).
When doing an ls -l on the file, telnet always shows the permissions this way:
Ignore the first dash, then break up the above into three groups of letters. If there's a dash where a letter should be, it means that there is no permission for those people.
Remember: the first 3 apply to user, the second 3 apply to group, and the third 3 apply to others.
Some FTP clients support changing permissions in a more graphical way. If you have Fetch for the Mac, you have an easy way to change permissions. Go to the file you want to change the permissions on, and highlight it. Under the Remote menu, select Change Permissions. A window will pop up showing the current permissions for the file you had highlighted. Click on the boxes to change permissions as needed.
WS_FTP accomplishes the same task as above. Just highlight the file you want to check, and right-click on it. A menu will pop up, then select CHMOD.
Below are solutions to some of the more common CGI script problems, in question and answer format. You will find a list of proper permission settings for the scripts we provide at the end.
When I activate my CGI program, I get back a page that says "Internal Server Error. The server encountered an internal error or mis-configuration and was unable to complete your request."
This is generally caused by a problem within the script. Log in via Telnet and test your script in local mode to get a better idea of what the problem is. To do this, go into the directory in which your script is located, then execute the script. To execute the script, you can do it by two ways:
1) Type "perl myscript.pl" (Perl being the language interpreter in this case).
2) Or simply type "myscript.pl" alone, that will work if the first line is well written to indicate the location of Perl.
The first one is useful to see if there's any error IN your script. The second one is useful to test if your "calling line" (the first line of the script) is okay, i.e. if you entered the right location of Perl.
I am being told "File Not Found," or "No Such File or Directory."
Upload your Perl or CGI script in ASCII mode, not binary mode.
When I test my Perl script in local mode (by Telnet), I have the following error: "Literal @domain now requires a back slash at myscript.pl line 3, within string. Execution of myscript.pl aborted due to compilation errors."
This is caused by a misinterpretation by Perl. You see, the "@" sign has a special meaning in Perl; it identifies an array (a table of elements). Since it cannot find the array named domain, it generates an error. You should place a back slash (\) before the "@" symbol to tell Perl to see it as a regular symbol, as in an email address.
I am getting the message "POST not implemented."
You are probably using the wrong reference for cgiemail. Use the reference /cgi-bin/cgiemail/mail.txt. Another possibility is that you are pointing to a cgi-bin script that you have not put in your cgi-bin directory. In general, this message really means that the web server is not recognizing the cgi-bin script you are calling as a program. It thinks it is a regular text file.
It's saying I don't have permission to access /
This error message means that you are missing your index.htm file. Note that files that start with a "." are hidden files. To see them, type ls -al. If you wish to FTP this file in, go to the home/yourdomain directory.
FormMail is a generic www form to e-mail gateway, which will parse the results of any form and send them to the specified user. This script has many formatting and operational options, most of which can be specified through the form, meaning you don't need any programming knowledge or multiple scripts for multiple forms. This also makes FormMail the perfect system-wise solution for allowing users form-based user feedback capabilities without the risks of allowing freedom of CGI access.
There is only one form field that you must have in your form, for FormMail to work correctly. This is the recipient field. Other hidden configuration fields can also be used to enhance the operation of FormMail on your site. The action of your form needs to point towards this script (obviously), and the method must be POST in capital letters.
Here's an example of the form fields to put in your form:
<FORM ACTION = "/cgi-sys/formmail.pl" METHOD = "POST"> <input type=hidden name="recipient" value="ANYONE@YOURDOMAIN.COM"> <input type=hidden name="subject" value="SUBJECT"> <input type=hidden name="return_link_title" value="TITLE"> <input type=hidden name="redirect" value="http://YOURDOMAIN.COM/PAGE.HTML">
The following are descriptions and proper syntax for fields you can use with FormMail.
Description: This form field allows you to specify to whom you wish for your form results to be mailed. Most likely you will want to configure this option as a hidden form field with a value equal to that of your email address.
Syntax: <input type=hidden name="recipient" value="firstname.lastname@example.org">
Description: The subject field will allow you to specify the subject that you wish to appear in the email that is sent to you after this form has been filled out. If you do not have this option turned on, then the script will default to a message subject: "WWW Form Submission".
Syntax: If you wish to choose what the subject is:
<input type=hidden name="subject" value="Your Subject">
To allow the user to choose a subject:
<input type=text name="subject">
Description: This form field will allow the user to specify their return email address. If you want to be able to return e-mail to your user, I strongly suggest that you include this form field and allow them to fill it in. This will be put into the From: field of the message you receive. If you want to require an email address with valid syntax, add this field name to the 'required' field.
Syntax: <input type=text name="email">
Description: The realname form field will allow the user to input their real name. This field is useful for identification purposes and will also be put into the From: line of your message header.
Syntax: <input type=text name="realname">
Description: If you wish to redirect the user to a different URL, rather than having them see the default response to the fill-out form, you can use this hidden variable to send them to a pre-made HTML page.
Syntax: To choose the URL they will end up at:
<input type=hidden name="redirect" value="http://yourdomain.com/to/file.html">
To allow them to specify a URL they wish to travel to once the form is filled out:
<input type=text name="redirect">
Description: You can require certain fields in your form to be filled in before the user can successfully submit the form. Simply place all field names that you want to be mandatory into this field, separated by commas. If the required fields are not filled in, the user will be notified of what they need to fill in, and a link back to the form they just submitted will be provided.
To use a customized error page, see "missing_fields_redirect"
Syntax: If you want to require that they fill in the email and phone fields in your form, so that you can reach them once you have received the mail, use the syntax like:
<input type=hidden name="required" value="email,phone">
Description: Allows you to have Environment variables included in the email message you receive after a user has filled out your form. Useful if you wish to know what browser they were using, what domain they were coming from or any other attributes associated with environment variables. The following is a short list of valid environment variables that might be useful:
REMOTE_HOST - Sends the host name making the request.
(Note: In our case, both REMOTE_HOST and REMOTE_ADDR are the same, since our servers don't do the reverse DNS look up needed to generate the true REMOTE_HOST string).
Syntax: If you wanted to find all the above variables, you would put the following into your form:
<input type=hidden name="env_report" value="REMOTE_HOST,REMOTE_ADDR,HTTP_USER_AGENT">
Description: This field allows you to choose the order in which you wish for your variables to appear in the email form that FormMail generates. You can choose to have the field sorted alphabetically or specify a set order in which you want the fields to appear in your mail message. By leaving this field out, the order will simply default to the order in which the browsers send the information to the script (which is usually the exact same order as they appeared in the form).
When sorting by a set order of fields, you should include the phrase "order:" as the first part of your value for the sort field, and then follow that with the field names you want to be listed in the email message, separated by commas.
Syntax: To sort alphabetically:
<input type=hidden name="sort" value="alphabetic">
To sort by a set field order:
<input type=hidden name="sort" value="order:name1,name2,etc...">
Description: print_config allows you to specify which of the config variables you would like to have printed in your e-mail message. By default, no config fields are printed to your email. This is because the important form fields, like email, subject, etc. are included in the header of the message. However some users have asked for this option so they can have these fields printed in the body of the message. The config fields that you wish to have printed should be in the value attribute of your input tag separated by commas.
Syntax: If you want to print the email and subject fields in the body of your message, you would place the following form tag:
<input type=hidden name="print config" value="email, subject">
Description: print_blank_fields allows you to request that all form fields are printed in the return HTML, regardless of whether or not they were filled in. FormMail defaults to turning this off, so that unused form fields aren't emailed.
Syntax: <input type=hidden name="print_blank_fields" value="1">
Description: This form field allows you to specify the title and header that will appear on the resulting page if you do not specify a redirect URL.
Syntax: If you wanted a title of 'Feedback Form Results':
<input type=hidden name="title" value="Feedback Form Results">
Description: This field allows you to specify a URL that will appear, as return_link_title, on the following report page. This field will not be used if you have the redirect field set, but it is useful if you allow the user to receive the report on the following page, but want to offer them a way to get back to your main page.
Syntax: <input type=hidden name="return_link_url" value="http://yourdomain.com/index.htm">
Description: This is the title that will be used to link the user back to the page you specify with return_link_url. The two fields will be shown on the resulting form page as:
Back to Main Page
Syntax: <input type=hidden name="return_link_title" value="Back to Main Page">
What is SSI?
Used properly, the SSI can help make your pages more responsive and can even help make maintaining your site an easier task.
Put simply, SSI is sort of like using your HTML server as a cut and paste editor. Here is basically what happens when your server handles a request for an SSI document. If you use SSI, you must rename the page so that it ends in .shtml so that the server knows to parse the page for SSI commands.
SSI also seems to be one of the better kept secrets around. In any web related book, they seem to get about 1 page for every 200 pages on CGI and FORMS. Well, I've never been one to leave you in the dark when it comes to being a better webmaster.
How to Use SSI
The syntax ofr an SSI include is as follows:
<!--#include file="mailform1.txt" -->
Where mailform1.txt is the path to the file that you want to be included. For instance if you have a file called file.shtml and you include the SSI
<!--#include file="mailform1.txt" -->
The contents of mailform1.txt will be displayed in file.shtml.
There are many good tutorials in SSI available on the Web. Here are a few that we recommend:
All text and images unless otherwise indicated are Copyright © 1999 - 2001 by Studio Braun.