We need to start this exercise by making sure that you are able to install and run simple CGI programs on Grace written in Perl.

Setup: Create a subdirectory in your 'www/409' directory on grace called "cgi". Remember to set the permissions so that the web server can read and execute both the contents _and_ the program files. (Example: chmod 755 first.cgi)

Create the Program File: Using a text editor type in the following program, _exactly_ as it appears below:

Install the Program File: If you created it on your PC or Mac, now upload it to your cgi subdirectory. Make sure you transfer the file in "ASCII" or "Text" mode and not "binary." Then login to grace and view the file using a Unix text editor (like pico or vi). Make sure it looks okay (are the line endings in the right place? are there strange characters? if there are problems, you may need to save it in a different format, or upload it differently...)

What should the output of this program be? (Describe it in your blog entry?)

Make sure you understand what the program is supposed to be doing, so you will recognize correct output when you see it.

Test the Program File: Now, run the program directly on Grace, by typing this command at the prompt:

perl first.cgi

If all goes well, your program should execute. If it doesn't, track down and fix the syntax errors until it runs.

Capture the output: To more accurately simulate how the web server will execute your program, use redirection of output to capture the output of your program into a text file. Try running your program a slightly different way:

first.cgi > firstout.txt

Notice we don't _have_ to use the "Perl" command at the command line.

Examine the output to make sure it is formed correctly by viewing the file firstout.txt. If everything looks okay, keep going. If not, see if you can find the problem.

Question to answer in your blog entry: What precedes the html in your output? Why would that need to be there?

Now you are ready to see if the program can be run as a cgi program.

Note: on some systems the program must end in a .cgi suffix regardless of the language in which it was written, in order to run as a cgi program. Grace is one of them. Some servers also require that all cgi files be placed in a "cgi-bin" directory in your main web directory, but Grace does not require this; you can place .cgi files anywhere in your web directory.

Test your cgi program by loading it in a browser (http://www.rit.edu/~yourid/409/cgi/first.cgi).

Create Another CGI Program: If that works, create a second cgi program--call it second.cgi. This second program will not produce a web page. All that it will do is output an http response header to send the user to a new location. Not surprisingly, this uses a Location: header, and works much like a html refresh meta-tag. It tells the browser to request another document at another location. Have the program redirect to your 409 personal page. (http://www.rit.edu/~yourid/409/).

Here's an example of a Location header:

Location: http://www.w3.org/pub/WWW/People.html

How would you output this? You use a print statement to output this type of header, of course. The header is for the browser and tells it to look elsewhere for a document. Remember to output a blank line after the header! There is no html output by this program and that means, you do not return content from your program (so what header don't you need?).

Test the Second Program: Create an index.html file for your cgi directory, and include a link to both cgi programs. When a user clicks on the link to the second.cgi program, s/he should be redirected immediately to your main 409 page.

Question to answer on your blog: Is this a useful thing? Why bother?