File Transfer Protocol (ftp) developed at Berkeley is a separate communication or connection program that is used automatically by some browsers. It can also be used explicity as a utility from your shell acount. The following is a description of the use of ftp from your shell account.
I'll assume that you have read the section on logging in to your shell account and familiarized yourself with the what you can do under the shell.
As under dos, a program or utility is started up by using its name on the command line. Commands generally take both options and arguments. The 'ftp' utility takes no options, but takes an optional single argument. The most efficient way to use ftp is with the argument. The argument is Fully Qualified Domain Name of a computer system on the internet for which your you actually have an account, or a computer system which allows "anonymous ftp login". If you have an account on the remote system then you will use the login name and password for that account. More likely you will be accessing an anonymous ftp site. These pages contain a link to a list of anonymous ftp sites.
What do anonymous ftp sites have that I might be interested in? Mostly, such sites are archives of various kinds of files: FAQ documents for various usenet news groups are contained in the archives of
rtfm.mit.edu
and
pit-manager.mit.edu
Archives of backissues of various electronic journals and magazines
are also frequently available from ftp sites. Software either
in binary or source code are also maintained at certain sites.
tsx-11.mit.edu
is a repository for source code of many programs that are
at the "beta stage".
Many documents directly concerned with internet standards
(RFC, FYI, STD) documents and structure are at
nic.merit.edu
and
farnet.org
This should pretty much explain what ftp sites are good for.
Accessing the site:
On the command line use, for example
ftp nic.merit.edu
This should make the ftp connection with nic.merit.edu.
Under heavy use, a site may refuse the connection and suggest
that you try later.
You don't have much choice.
There is a more elaborate method.
Use as command
ftp
This returns an ftp prompt but makes no connection
When the connection is made, you will probably see a full screen of written material concrning the site and its use. Remember that your use of an "anonymous ftp site" is not a right, but a privilege. Someone is opening their home to you, computer though it may be, and the same common sense rules of courtesy apply. Some considerations, however, are not so much common sense and need little explanations as we go along here. Read the opening screen message carefully, and certainly comply with any requests. Even if the site does not demand it, it is conventional courtesy to login using "anonymous" as the login name and your email address as the password. Clearly "anonymous ftp login" is not exactly anonymous. Bear in mind that some ftp sites can capture your email address regardless of what you enter; it is best not to play games.
So are now logged in by ftp and are presumably looking for something. There are various command that ftp understands, most of which, not surprisingly, have to do with file transfer. You do *not* have to stay on line and connected to the remote site to search the entire archive, by hand. Unlike an http connection, which gracefully connects and disconnects to the designated URL as needed, an ftp connection is fixed. This puts the onus of politeness more squarely on you. In this case, "politeness" means not only conforming to the house rules, but by limiting your connect time and generally *not* using the very powerful and system intensive command
ls -lR = list in long format recursively, every file
and directory found beneath the present working
directory (See already prepared files below.)
Remember that that there are quite literally millions of people
who are potential accessors for this site.
You limit your connect time by knowing what you're doing.
This document is supposed to give you the requisite knowledge
to be polite.
Most sites keep index files
that can be recognized by their name.
When you are first logged in and see the
ftp>
prompt, there are two commands that useful for orienting yourself.
The command 'pwd' is recognized and should be familiar.
The most probable response will be "/", indicating that you are positioned
at the top of the file system.
The command 'ls' or the command 'dir' is recognized and will list the
contents of the root directory.
The file and directory names should be in the rightmost column.
Look for files whose names are any of:
Possible name extensions
README .txt
index, Index, INDEX .zip
ls-lR, ls-Rl .gz
.z
.Z
.tar
.tar.gz
These are the files should be downloaded to the server of your
access provider or to your own computer if appropriate,
and read first.
Find what you want, and then reconnect to download the
desired file(s).
Notice, with an 'ls' command, the leftmost character will be
either '_' signifying a file or 'd' signifying a directory.
The output of 'ls' under ftp is same as under a unix shell.
You cannot download an directory as any attempt to do so will
readily show.
File name extensions and their significance:
none
.txt
A standard ascii text file.
.z
Ambiguous in compression scheme, but -
a "binary" file. Possible compression schemes:
zip, pkzip, "old" unix pack.
.Z
A file that has been compressed by the unix 'compress' utility -
a "binary" file.
.zip
A file(s) or directory that has been compressed by either
'zip' or 'pkzip' - a "binary" file. NOTE: zipping can be
nested: after an 'unzip' there may be files that still need
to be unzipped again.
.gz
A file that has been compressed by the GNU gzip/gunzip utilities -
a "binary" file.
.tar
Usually a directory archive file created by the venerable 'tar'
(originally "Tape ARchive") utility of unix - a binary file.
.tar.gz
A tar archive which has then been gzip'd. This may be the
cleanest way of archiving entire directories, and the easiest
to undo - also a binary file.
Why do I bother with such sordid details? Your ftp connection supports two modes of transfer
"ascii" and "binary"
One of these modes is set as the default when you finish
logging in. Although some sites have smart software that
will set the transfer mode that is appropriate to the file
you are downloading, some do not.
1) ascii files dowloaded in either mode will give good files.
2) binary files dowloaded in binary mode will give good files.
3) binary files dowloaded in ascii mode will give *garbage*.
On most systems you can and should, as a matter of course set the
appropriate transfer mode by issuing as a command to ftp either
"ascii" or "binary".
Changing to the Appropriate Directory
The change directory command 'cd' works in ftp just as it
does from a unix shell.
The command 'cdup' is an alias for 'cd ..'.
Sometimes, backing up on an ftp command line may not work and
instead just generates '^H' characters which are literal backspaces.
If you encounter the problem, just hit the ENTER key and be prepared
for an error message about "no such file or directory".
It pays to type carefully.
If the pathname of your goal directory is long, try taking it in steps.
An 'ls' or two along the way is fine.
Downloading a single file
Now, you've gotten yourself positioned in the right directory,
and an 'ls' has shown the right file name.
Be sure that it *is* a file and not a directory.
(The following will work for only *one* file.)
ftp> get filename
where filename is the name of the file you want.
Remember, you are accessing a unix system: file names are
case sensitive.
Type any upper or lower case letters exactly.
1) Some flavors of generic unix allow very long file names,
and some people make use of this freedom.
Just take entering the file name slowly and accurately.
2) There are certain characters that have special meaning to
unix shell. These are called metacharacters; more mundanely
in DOSese they are referred to as "wild cards". It has
been convention and practice in years of unix past *not*
to use these metachracters in the naming of files and
directories, precisely because it makes referencing the
files and directories so named difficult, clumsey and
arcane. That convention is now sometimes *not* adhered to.
The assumption behind their use is either 'let's be perverse'
or that the user knows unix and will not be fooled.
The standard shell metacharacters that mess up referencing
and that are used, are:
[ ] ( ) { } < > ? * & $
If you see any of these characters in the filename, when typing the
filename for the ftp "get", precede the metacharacter with a backslash
(not the forward leaning slash used to construct pathnames).
The backslash is the unix "escape character".
An ftp "get" allows a second argument.
The command line
ftp> get filename file2
will retrieve "filename" on the remote ftp server copying it
to your server under a new name "file2".
Dowloading multiple files
To dowload more than one file with a single command,
replace "get" with "mget". The command line will look like
ftp> mget file1 file2 file3 ... filen
The locution
ftp> mget file?
may work on some systems, but most often, the locution
ftp> mget *
is disallowed.
When using "mget", there is an automatic interrogation of the
user (y/n) to transfer the next file.
You can turn this off by
ftp> prompt
This is a toggle switch command that turns such prompting on and off.
If the impending transfer by either "get" or "mget" is known to be large
it is helpful to issue the command
ftp> tick
before the file transfer command.
This will cause a display of the progress of the transfer and
show up any hanging that might occur during the transfer.
This prevents sitting there for half an hour just woundering
whether the file is bigger than you thought.
When the file transfer has terminated and the ftp-prompt has returned
ftp> bye
will disconnect the remote ftp connection and return your shell
prompt.
I've discussed only the *essential* ftp commands. See the crib sheet below for the full list. Most of them you will not need.
A final comment on Mirrors and Politeness. For much accessed archives and repositories there are mirror sites which duplicate the files of a primary repository. It is good netequette to retrieve from the closest site. If you can retrieve files from a mirror site of material originating in Finland, do so rather than accessing the originating site.
The command syntax of ftp is designed so that it can be invoked and manipulated within "shell scripts" and so that ftp usage can be automated. To go further than that brief comment would mean requiring a greater knowledge of unix shells and their use as programing languages.
FTP CRIB SHEET
Syntax
ftp <Fully-Qualified-Domain>
ftp>
or
ftp
ftp> open <Fully-Qualified-Domain>
Ftp Commands
ftp> help
Commands may be abbreviated. Commands are:
! debug mget pwd status
$ dir mkdir quit struct
account disconnect mls quote system
append form mode recv sunique
ascii get modtime reget tenex
bell glob mput rstatus tick
binary hash newer rhelp trace
bye help nmap rename type
case idle nlist reset user
cd image ntrans restart umask
cdup lcd open rmdir verbose
chmod ls prompt runique ?
close macdef proxy send
cr mdelete sendport site
delete mdir put size
Ftp command synopsis:
! <cmd> Run command on local system
$ execute macro
account send account command to remote server
append Set to append transferred file to an existing one
ascii Set xfer protocol for text files
bell beep when command completed
binary Set xfer protocol for text files
bye Close ftp connection
case toggle mget upper/lower case id mapping
cd Change directory on remote system
cdup = cd .. on remote system
chmod chmod on remote system
close = bye
cr on/off toggle of using ^M at EOL or not
delete delete remote file
debug toggle/set debugging mode
dir List directory contents in DOS format
disconnect terminate ftp session (don't exit ftp)
form set file transfer format
get [get rfile | get rfile lfile] Transfer one file to local
glob toggle metacharacter expansion of local file names
hash on/off toggle: Show stats on bytes xferred and yet to be xferred
help [help | help <cmd>] Display above message without argument
idle get (set) idle timer on remote side
image = binary
lcd change directory on local system
ls List in unix ls -l style
macdef define a macro
mdelete delete multiple files
mdir list contents of multiple remote directories
mget [get rfile1 rfile2 ...] get multiple files
mkdir mkdir on remote system
mls list contents of multiple remote directories
mode set file transfer mode
mkdir Make directory on remote system
mput [put rfile1 rfile2 ...] put multiple files
newer get file if remote file is newer than local file
nmap set templates for default file name mapping
nlist nlist contents of remote directory
ntrans set translation table for default file name mapping
open open connection to named site
prompt toggle on/off default prompts between multiple get/put
proxy issue command on alternate connection
sendport toggle use of PORT cmd for each data connection
put [put lfile | put lfile rfile] Transfer one file to remote
pwd pwd on remote system
quit = bye
quote send arbitrary ftp command
recv receive file
reget get file restarting at end of local file
rstatus show status of remote machine
rhelp get help from remote server
rename rename file
reset clear queued command replies
restart restart file transfer at bytecount
rmdir Remove directory on remote system
runique toggle store unique for local files
send send one file
site send site specific command to remote server
Try "rhelp site" or "site help" for more information
size show size of remote file
status show current status
struct set file transfer structure
system show remote system type
sunique toggle store unique on remote machine
tenex Set transfer mode to DEC TOPS-10 format
tick toggle printing byte counter during transfers
trace toggle packet tracing
type Display the transfer mode: ascii, binary, image, tenex
user Specify user name to remote system
umask get (set) umask on remote side
verbose toggle verbose mode
? = help
Useful Locutions (that don't always work!):
ftp> ls *.txt | more
Displays the listing through the paginator
ftp> get README | more
Displays the file README rather than transferring to local system
ftp> get README "| grep <pattern>"
Displays the lines of README with pattern
^C Should stop a file transfer, if not
^\ will most certainly do it.