lftp-2.6.3: description + notes
This package `lftp' contains the following components:
lftp
sophisticated command line file transfer program (ftp/http client, also supports fish protocol and file URLs).
lftpget
shell script for downloading by URL, it calls `lftp -c'.
lftp is written in C++ and uses a cooperative-threaded model.

lftp

lftp is command line file transfer program. It supports FTP and HTTP protocols. GNU Readline library is used for input.

Low level stuff supported: ftp proxy, http proxy, ftp over http, opie/skey, fxp transfers, automatic retrying on non-fatal errors and timeouts, ipv6, socks. See FEATURES for more detailed list of features.

Every operation in lftp is reliable, that is any non-fatal error is ignored and the operation is retried. So if downloading breaks, it will be restarted from the point automatically. Even if ftp server does not support REST command, lftp will try to retrieve the file from the very beginning until the file is transferred completely.

lftp has shell-like command syntax allowing you to launch several commands in parallel in background (&). It is also possible to group commands within () and execute them in background. All background jobs are executed in the same single process. You can bring a foreground job to background with ^Z (c-z) and back with command `wait' (or `fg' which is alias to `wait'). To list running jobs, use command `jobs'. Some commands allow redirecting their output (cat, ls, ...) to file or via pipe to external command. Commands can be executed conditionally based on termination status of previous command (&&, ||).

If you exit lftp when some jobs are not finished yet, lftp will move itself to nohup mode in background. The same happens when you have a real modem hangup or when you close an xterm.

lftp has builtin mirror which can download or update a whole directory tree. There is also reverse mirror (mirror -R) which uploads or updates a directory tree on server.

There is command `at' to launch a job at specified time in current context, command `queue' to queue commands for sequential execution for current server, and much more.

On startup, lftp executes /etc/lftp.conf and then ~/.lftprc and ~/.lftp/rc. You can place aliases and `set' commands there. Some people prefer to see full protocol debug, use `debug' to turn the debug on. Use `debug 3' to see only greeting messages and error messages.

lftp has a number of settable variables. You can use `set -a' to see all variables and their values or `set -d' to see list of defaults. Variable names can be abbreviated and prefix can be omitted unless the rest becomes ambiguous.

Use command `help' or read documentation (man lftp) to learn more.

If lftp was compiled with ssl support, then it includes software developed by the OpenSSL Project for use in the OpenSSL Toolkit. (http://www.openssl.org/)

Where to get

By FTP: By HTTP: By CVS: See also home page `http://lftp.yar.ru/'.

Internals

All this is based on SMTask class which implements non-preemptive multitasking via Do method. The method Do does a little bit of work, sets wake up condition (block member) and returns.

The class Ftp allows reliable deliver of files via ftp protocol, it hides all the details from application and allows asynchronous operation. Reconnect and reget are done as necessary. It can also speed up ftp operations by sending several commands at once and then checking all the responses. It seems this sometimes does not work, so it is disabled by default. To turn it on, use `set sync-mode n' in lftp or --async-mode for ftpget.

Note that sending several commands is considered as violation or protocol, but RFC959 says: ``The user-process sending another command before the completion reply would be in violation of protocol; but server-FTP processes should queue any commands that arrive while a preceding command is in progress.''

It is known that some network software dealing with address translation works incorrectly in case of several FTP commands in one network packet.

Systems

The package is known to compile on Solaris2.5(gcc), Linux, FreeBSD, NetBSD, SCO v5.0(gcc), IRIX(gcc), Tru64(gcc) and other systems. If you can't compile it on your system, let me know. It is possible that lftp version 2.0 can be compiled with non-gcc compilers since it does not have gcc-isms, and it was successfully compiled by Sun C++ v5.0 compiler using CXXFLAGS="-compat=4 -features=bool".

Mailing list

There is a mailing list for discussion of lftp and announcements. It is managed by majordomo; to subscribe, send mail to majordomo@uniyar.ac.ru with `subscribe lftp' in body of message; to send letters to the list, send them to lftp@uniyar.ac.ru; to unsubscribe, send mail to majordomo@uniyar.ac.ru with `unsubscribe lftp' in body of message. This is low volume list.

There is also list lftp-devel@uniyar.ac.ru for snapshot announcements and other development. These lists are archived at

Author

Author: Alexander V. Lukyanov (lav@yars.free.net)
My home page: http://www.yars.free.net/~lav/

Other people have contributed to lftp development, see THANKS and ChangeLog files.

Comments and bug reports are welcome. Please send them to the list: lftp@uniyar.ac.ru.

License

Copyright (c) 1996-2002 by Alexander V. Lukyanov (lav@yars.free.net)

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

In addition, as a special exception, permission is given to link the code of this release of lftp with the OpenSSL project's "OpenSSL" library (or with modified versions of it that use the same license as the "OpenSSL" library), and distribute the linked executables. You must obey the GNU General Public License in all respects for all of the code used other than "OpenSSL". If you modify this file, you may extend this exception to your version of the file, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.

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