1 Copyright © 2002 Pearson Education, Inc.. 2 Chapter 2 Getting Started.

1 Copyright © 2002 Pearson Education, Inc.


Chapter 2

Getting Started


What You Need to Get Started

Getting the appropriate FTP or Telnet software Connecting to the Web server Setting up your directories. Getting the location of the Perl interpreter.


Connecting with Telnet

Connect to the Internet Start Telnet.

» On a Windows PC start Microsoft Telnet for Windows by clicking Start, Run, telnet.

Connect to your Web server with Telnet. Log into the server.


An Initial Telnet Sreen


Successful Telnet Login


Connecting with FTP

Connect to the Internet. Start FTP. Connect to your Web server with FTP.


An Initial FTP Login Screen


A Successful FTP Login Screen


Navigating UNIX Directories

/ - Operating system files/

home /home - ISP User directories

perlpgm /home/perlpgm -My files

and directories

bin etc . . .Some UNIX system

directories

usr

jsmith/home/jsmith -

jsmith's files and directories.

. . .


Navigating UNIX Directories - 2

/home/perlpgm /home/perlpgm -My files and directories.

/home/perlpgm/perl-pgm-www/cgi-bin- Where I need to place my web application

programs.

data

cgi-bin

/home/perlpgm/perl-pgm-www -Where I need to place my HTML files.

perl-pgm-www/home/perlpgm/data -A directory I place data I want on

the server but not on the Internet.


Some UNIX Navigation Commands

Command Command’s Effect

pwd Prints the Working Directory. Outputs the directory path of the

current directory.

ls LiSts the files and directories in the current directories. Returns all

of the files and directories in the current directory.

cd dir_name Changes the Directory to the directory named dir_name. Changes

the current directory to the one you specify. (Note that you can

navigate up one directory by executing cd .. —that is, cd

followed by two periods.)


Some UNIX Navigation Commands

UnixCommands


Navigating UNIX Directories with FTP

Homediron web server

C:\Tempon PC


Finding The Location Of Perl

Perl interpreter

» A program that translates Perl program commands into commands that are understandable to a computer.

» Runs your Perl programs and generates any output.

» Its command name is simply perl.

» It can be installed in any of several places on a Web server.


Finding Location Of Perl

Find the location of Perl Interpreter Telnet onto Web Server enter:

» which perl » where is perl

Perl InterpreterLocation


Starting Your Program Development Process

Each time you develop and run a program:» Create a program file and copy (or save) it into the

correct directory.» Change your program’s access permissions.» Check your program’s syntax. » Run your program.


Create Your Program File

Editors are computer applications that enable you to create, change, and save files» Microsoft Windows, Notepad is a simple editor

that works well for Perl development.

» On UNIX systems, the Pico, Vi, and Emacs editors are popular choices.

» Will describe the use of Pico on a UNIX Web Server.


Starting Pico

Telnet into Web Server and enter “pico”


Starting Your First Program

Start Editor and enter the following:1. #!/usr/bin/perl 2. # This program prints out a simple

message

3. print “Steady Plodding Brings

Prosperity\n”;


Program Entered in Pico


Run The Program

Save the program file on the web server. Enter the full path to the program file to run. For example

» /home/perlpgm/perl-pgm-www/cgi-bin/simple1.cgi

Program File

Home Directory

Directories On Web Server


Change the Program’s Permissions On A Unix Web

Server

UNIX access permissions are used to define the access rights of your files» read permissions define if the file can be read» write permissions define if the file can be changed, » execute permissions define if the file can be

executed as a program You set access permissions for your user ID,

your user ID’s group, and everyone else


Use The chmod command

chmod 755 /home/perlpgm/perl-pgm-www/cgi-bin/simple1.cgiThe UNIX chmod

commandchanges

file permissions

Your personal access permissions to the file.

Your group's access permissions to the file.

Any other user's access permissions to the file.

The file that you are changingread, write, and execution access

permissions to.


Use The chmod command

Digit Permissions Meaning

7 Gives read, write, or execute access to the file

6 Gives read or write access to the file, but not execute access5 Gives read or execute access to the file, but not write access4 Gives read access to the file, but not write or execute access


Change the Program’s Permissions On A Unix Web

Server

» chmod 777 simple1.cgi - end-user and his/her work group and anyone else to read, write, or execute the file simple1.cgi.

» chmod 755 simple1.cgi - end-user can read, write, or execute the file simple1.cgi, but everyone else can only read or execute it.

» chmod 644 simple1.cgi - you can read or write the file simple1.cgi, but everyone else can only read it. (Good for data files).


Setting Permissions with FTP on a UNIX Web Server

1. Log into the Web server using the FTP command.

2.Navigate to the appropriate directories on the Web server.

3.Select the file you want to change on your Web server, then right -click it. A drop-down menu will appear. Select FTP commands, and then chmod. (See Next Slide).

4. Select the desired read, write, and execute access permissions for your user ID, your group, and anyone else.


An FTP Change Permission Screen


Check and Correct Your Program’s Syntax

syntax checking - verifies that program statements are grammatically correct as specified by the program language grammar» Check the syntax of your programs before

attempting to run them.


To Check Your Program Syntax

(on a UNIX Web Server) establish a Telnet session, navigate to the directory that contains the file, enter perl –c filename, where filename is

the program file whose syntax you want to. For example,

–cd perl-pgm-www/cgi-bin–perl –c simple1.cgi

If no syntax errors then receive:– simple1.cgi syntax OK


Program with Syntax errors

Missingquote mark


Running Your Program

At least two different ways to run your Perl programs:» Directly on a Web server or PC without a

browser» Using your browser over the Internet.


Running Your Program - On A PC

1. Open a MS-DOS prompt window. » Click Start, Run and then enter command.

2. Run the program. » At the MS-DOS prompt, enter the location of Perl, followed

by the location of your program:» C:\Perl\bin\Perl C:\temp\simple1.pl» Perl C:\temp\simple1.pl » You Can also use cd

–cd C:\temp

–Perl simple1.pl


Getting Ready to Run Your Program Over the

Internet

1. To use a browser over the Internet, add the following MIME content-type line:

print “Content-type: text/html\n\n”;.

1.#!/usr/bin/perl

2.print “Content-type: text/html\n\n”;

3.# This program prints out a simple message

4.print “Steady Plodding Brings Prosperity\n”;


Change Program Process

1. Edit the program

2. Change the program.

3. Save the file.

4. Check the program’s syntax.

5. Run the program.


Running Your Program Over the Internet

1. Connect to the Internet.

2. Start your browser.

3. Enter the URL or Web address to your file

4. Check the program’s syntax.

5. Run the program.

For example, assume saved the in a file called simple2.cgi in my cgi-bin directory on the Web server. Can execute by the following: http://perl-pgm.com/cgi-bin/simple2.cgi


Output Of Program Executed Over the Internet


Dealing with Problems

Many Web servers redirect the errors from CGI programs into a separate error log located on the server. » You may receive a generic, cryptic message

when running program’s with errors. » Two common messages are Internal Server

Error (Figure 2.17) and 500 Server Error.


Some Things to Check Verify the program syntax. Verify the access permission. Verify the file has the proper extension. Verify the program is stored in the correct directory. Verify the correct Web address to your program. Verify the first line has the correct of the Perl

interpreter. Confirm the accuracy of your MIME Content-type line.


An Internet Server Error


Generating HTML Statement from Perl

Programs

1. #!/usr/bin/perl2. print "Content-type: text/html\n\n";3. print "<HTML> <HEAD> <TITLE> Example </TITLE></HEAD>";

4. print "<BODY>";5. print "<B><Font Size=5>This is a Test </FONT></B>";

6. print "A very Interesting test";

7. print "</BODY></HTML>";


Program Output


Summary

There are several different configurations you can use to develop CGI/Perl programs.» Using FTP and Telent are common

Steps to create a program: create with editor, enter program, set permissions, check syntax, and run the program.

Two statements are required:» First line identifies Perl interpreter location.

» Second line specifies the MIME Content-type.

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1 Copyright © 2002 Pearson Education, Inc.. 2 Chapter 2 Getting Started.

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