Transferring Files (FTP)

One of the backbones of the Internet is the ability to transfer files. There are thousands of fcservers from which you can download files. For the latest graphic board drivers to the best in shareware to the entire set of UNIX sources, ftp is the answer.

The program in ftp.pl downloads the Perl FAQ in compressed format from ftp.cis.ufl.edu and displays a directory in two formats.

It operates as follows:

• Turn on the warning compiler option. Load the ftplib library.
• Turn on the strict pragma.
• Declare a variable to hold directory listings.
• Turn debugging mode on. This will display all of the protocol commands and responses on STDERR.
• Connect to the ftp server providing a userid of anonymous and your email address as the password.
• Use the list() function to get a directory listing without first changing to the directory.
• Change to the /pub/perl/faq directory.
• Start binary mode. This is very important when getting compressed files or executables.
• Get the Perl FAQ file.
• Use list() to find out which files are in the current directory and then print the list.
• Use dir() to find out which files are in the current directory andthen print the list.
• Turn debugging off.
• Change to the /pub/perl/faq directory.
• Use list() to find out which files are in the current directory and then print the list.

The Perl code for ftp.pl is as follows:

#!/usr/bin/perl -w


require('ftplib.pl');
use strict;


my(@dirList);


ftp::debug('ON');
ftp::open('ftp.cis.ufl.edu', 'anonymous', 'medined@planet.net') or die($!);


@dirList = ftp::list('pub/perl/faq');


ftp::cwd('/pub/perl/faq');
ftp::binary();
ftp::gets('FAQ.gz');


@dirList = ftp::list();
print("list of /pub/perl/faq\n");
foreach (@dirList) {
print("\t$_\n");


}
@dirList = ftp::dir();
print("list of /pub/perl/faq\n");
foreach (@dirList) {
print("\t$_\n");
}
ftp::debug();
ftp::cwd('/pub/perl/faq');
@dirList = ftp::list();
print("list of /pub/perl/faq\n");
foreach (@dirList) {
print("\t$_\n");
}

This program displays:

<< 220 flood FTP server (Version wu-2.4(21) Tue Apr 9 17:01:12 EDT 1996) 
ready.
>> user anonymous
<< 331 Guest login ok, send your complete e-mail address as password.
>> pass .....
<< 230-                     Welcome to the
<< 230-                  University of Florida
.


.


.
<< 230 Guest login ok, access restrictions apply.
>> port 207,3,100,103,4,135
<< 200 PORT command successful.
>> nlst pub/perl/faq
<< 150 Opening ASCII mode data connection for file list.
<< 226 Transfer complete.
>> cwd /pub/perl/faq
<< 250 CWD command successful.
>> type i
<< 200 Type set to I.
>> port 207,3,100,103,4,136
<< 200 PORT command successful.
>> retr FAQ.gz
<< 150 Opening BINARY mode data connection for FAQ.gz (75167 bytes).
<< 226 Transfer complete.
>> port 207,3,100,103,4,138
<< 200 PORT command successful.
>> nlst
<< 150 Opening BINARY mode data connection for file list.
<< 226 Transfer complete.
list of /pub/perl/faq
 FAQ
 FAQ.gz
>> port 207,3,100,103,4,
139
<< 200 PORT command successful.
>> list
<< 150 Opening BINARY mode data connection for /bin/ls.
<< 226 Transfer complete.
list of /pub/perl/faq
 total 568
 drwxrwxr-x   2 1208     31           512 Nov  7  1995 .
 drwxrwxr-x  10 1208     68           512 Jun 18 21:32 ..
 -rw-rw-r--   1 1208     31        197446 Nov  4  1995 FAQ
 -rw-r--r--   1 1208     31         75167 Nov  7  1995 FAQ.gz
list of /pub/perl/faq
 FAQ
 FAQ.gz

Make sure that you can pick out the different ftp commands and responses in this output. Notice that the ftp commands and responses are only displayed when the debugging feature is turned on.