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(zsh.info)The zsh/zftp Module
The zsh/zftp Module
===================
The zsh/zftp module makes available one builtin command:
zftp SUBCOMMAND [ ARGS ]
The zsh/zftp module is a client for FTP (file transfer protocol).
It is implemented as a builtin to allow full use of shell command
line editing, file I/O, and job control mechanisms. Often, users
will access it via shell functions providing a more powerful
interface; a set is provided with the zsh distribution and is
described in Note: Zftp Function System. However, the zftp
command is entirely usable in its own right.
All commands consist of the command name zftp followed by the name
of a subcommand. These are listed below. The return status of
each subcommand is supposed to reflect the success or failure of
the remote operation. See a description of the variable
ZFTP_VERBOSE for more information on how responses from the server
may be printed.
Subcommands
-----------
open HOST [ USER [ PASSWORD [ ACCOUNT ] ] ]
Open a new FTP session to HOST, which may be the name of a TCP/IP
connected host or an IP number in the standard dot notation.
Remaining arguments are passed to the login subcommand. Note that
if no arguments beyond HOST are supplied, open will _not_
automatically call login. If no arguments at all are supplied,
open will use the parameters set by the params subcommand.
After a successful open, the shell variables ZFTP_HOST, ZFTP_IP
and ZFTP_SYSTEM are available; see `Variables' below.
login [ NAME [ PASSWORD [ ACCOUNT ] ] ]
user [ NAME [ PASSWORD [ ACCOUNT ] ] ]
Login the user NAME with parameters PASSWORD and ACCOUNT. Any of
the parameters can be omitted, and will be read from standard
input if needed (NAME is always needed). If standard input is a
terminal, a prompt for each one will be printed on standard error
and PASSWORD will not be echoed. If any of the parameters are not
used, a warning message is printed.
After a successful login, the shell variables ZFTP_USER,
ZFTP_ACCOUNT and ZFTP_PWD are available; see `Variables' below.
This command may be re-issued when a user is already logged in, and
the server will first be reinitialized for a new user.
params [ HOST [ USER [ PASSWORD [ ACCOUNT ] ] ] ]
params -
Store the given parameters for a later open command with no
arguments. Only those given on the command line will be
remembered. If no arguments are given, the parameters currently
set are printed, although the password will appear as a line of
stars; the return value is one if no parameters were set, zero
otherwise.
Any of the parameters may be specified as a `?', which may need to
be quoted to protect it from shell expansion. In this case, the
appropriate parameter will be read from stdin as with the login
subcommand, including special handling of PASSWORD. If the `?' is
followed by a string, that is used as the prompt for reading the
parameter instead of the default message (any necessary
punctuation and whitespace should be included at the end of the
prompt). The first letter of the parameter (only) may be quoted
with a `\'; hence an argument "\\$word" guarantees that the string
from the shell parameter $word will be treated literally, whether
or not it begins with a `?'.
If instead a single `-' is given, the existing parameters, if any,
are deleted. In that case, calling open with no arguments will
cause an error.
The list of parameters is not deleted after a close, however it
will be deleted if the zsh/zftp module is unloaded.
For example,
zftp params ftp.elsewhere.xx juser '?Password for juser: '
will store the host ftp.elsewhere.xx and the user juser and then
prompt the user for the corresponding password with the given
prompt.
test
Test the connection; if the server has reported that it has closed
the connection (maybe due to a timeout), return status 2; if no
connection was open anyway, return status 1; else return status 0.
The test subcommand is silent, apart from messages printed by the
$ZFTP_VERBOSE mechanism, or error messages if the connection
closes. There is no network overhead for this test.
The test is only supported on systems with either the select(2) or
poll(2) system calls; otherwise the message `not supported on this
system' is printed instead.
The test subcommand will automatically be called at the start of
any other subcommand for the current session when a connection is
open.
cd DIRECTORY
Change the remote directory to DIRECTORY. Also alters the shell
variable ZFTP_PWD.
cdup
Change the remote directory to the one higher in the directory
tree. Note that cd .. will also work correctly on non-UNIX
systems.
dir [ ARGS... ]
Give a (verbose) listing of the remote directory. The ARGS are
passed directly to the server. The command's behaviour is
implementation dependent, but a UNIX server will typically
interpret ARGS as arguments to the ls command and with no
arguments return the result of `ls -l'. The directory is listed to
standard output.
ls [ ARGS ]
Give a (short) listing of the remote directory. With no ARGS,
produces a raw list of the files in the directory, one per line.
Otherwise, up to vagaries of the server implementation, behaves
similar to dir.
type [ TYPE ]
Change the type for the transfer to TYPE, or print the current type
if TYPE is absent. The allowed values are `A' (ASCII), `I'
(Image, i.e. binary), or `B' (a synonym for `I').
The FTP default for a transfer is ASCII. However, if zftp finds
that the remote host is a UNIX machine with 8-bit byes, it will
automatically switch to using binary for file transfers upon open.
This can subsequently be overridden.
The transfer type is only passed to the remote host when a data
connection is established; this command involves no network
overhead.
ascii
The same as type A.
binary
The same as type I.
mode [ S | B ]
Set the mode type to stream (S) or block (B). Stream mode is the
default; block mode is not widely supported.
remote FILES...
local [ FILES... ]
Print the size and last modification time of the remote or local
files. If there is more than one item on the list, the name of the
file is printed first. The first number is the file size, the
second is the last modification time of the file in the format
CCYYMMDDhhmmSS consisting of year, month, date, hour, minutes and
seconds in GMT. Note that this format, including the length, is
guaranteed, so that time strings can be directly compared via the
[[ builtin's < and > operators, even if they are too long to be
represented as integers.
Not all servers support the commands for retrieving this
information. In that case, the remote command will print nothing
and return status 2, compared with status 1 for a file not found.
The local command (but not remote) may be used with no arguments,
in which case the information comes from examining file descriptor
zero. This is the same file as seen by a put command with no
further redirection.
get FILE [...]
Retrieve all FILEs from the server, concatenating them and sending
them to standard output.
put FILE [...]
For each FILE, read a file from standard input and send that to
the remote host with the given name.
append FILE [...]
As put, but if the remote FILE already exists, data is appended to
it instead of overwriting it.
getat FILE POINT
putat FILE POINT
appendat FILE POINT
Versions of get, put and append which will start the transfer at
the given POINT in the remote FILE. This is useful for appending
to an incomplete local file. However, note that this ability is
not universally supported by servers (and is not quite the
behaviour specified by the standard).
delete FILE [...]
Delete the list of files on the server.
mkdir DIRECTORY
Create a new directory DIRECTORY on the server.
rmdir DIRECTORY
Delete the directory DIRECTORY on the server.
rename OLD-NAME NEW-NAME
Rename file OLD-NAME to NEW-NAME on the server.
site ARGS...
Send a host-specific command to the server. You will probably
only need this if instructed by the server to use it.
quote ARGS...
Send the raw FTP command sequence to the server. You should be
familiar with the FTP command set as defined in RFC959 before doing
this. Useful commands may include STAT and HELP. Note also the
mechanism for returning messages as described for the variable
ZFTP_VERBOSE below, in particular that all messages from the
control connection are sent to standard error.
close
quit
Close the current data connection. This unsets the shell
parameters ZFTP_HOST, ZFTP_IP, ZFTP_SYSTEM, ZFTP_USER,
ZFTP_ACCOUNT, ZFTP_PWD, ZFTP_TYPE and ZFTP_MODE.
session [ SESSNAME ]
Allows multiple FTP sessions to be used at once. The name of the
session is an arbitrary string of characters; the default session
is called `default'. If this command is called without an
argument, it will list all the current sessions; with an argument,
it will either switch to the existing session called SESSNAME, or
create a new session of that name.
Each session remembers the status of the connection, the set of
connection-specific shell parameters (the same set as are unset
when a connection closes, as given in the description of close),
and any user parameters specified with the params subcommand.
Changing to a previous session restores those values; changing to
a new session initialises them in the same way as if zftp had just
been loaded. The name of the current session is given by the
parameter ZFTP_SESSION.
rmsession [ SESSNAME ]
Delete a session; if a name is not given, the current session is
deleted. If the current session is deleted, the earliest existing
session becomes the new current session, otherwise the current
session is not changed. If the session being deleted is the only
one, a new session called `default' is created and becomes the
current session; note that this is a new session even if the
session being deleted is also called `default'. It is recommended
that sessions not be deleted while background commands which use
zftp are still active.
Parameters
----------
The following shell parameters are used by zftp. Currently none of
them are special.
ZFTP_TMOUT
Integer. The time in seconds to wait for a network operation to
complete before returning an error. If this is not set when the
module is loaded, it will be given the default value 60. A value
of zero turns off timeouts. If a timeout occurs on the control
connection it will be closed. Use a larger value if this occurs
too frequently.
ZFTP_IP
Readonly. The IP address of the current connection in dot
notation.
ZFTP_HOST
Readonly. The hostname of the current remote server. If the host
was opened as an IP number, ZFTP_HOST contains that instead; this
saves the overhead for a name lookup, as IP numbers are most
commonly used when a nameserver is unavailable.
ZFTP_SYSTEM
Readonly. The system type string returned by the server in
response to an FTP SYST request. The most interesting case is a
string beginning "UNIX Type: L8", which ensures maximum
compatibility with a local UNIX host.
ZFTP_TYPE
Readonly. The type to be used for data transfers , either `A' or
`I'. Use the type subcommand to change this.
ZFTP_USER
Readonly. The username currently logged in, if any.
ZFTP_ACCOUNT
Readonly. The account name of the current user, if any. Most
servers do not require an account name.
ZFTP_PWD
Readonly. The current directory on the server.
ZFTP_CODE
Readonly. The three digit code of the last FTP reply from the
server as a string. This can still be read after the connection
is closed, and is not changed when the current session changes.
ZFTP_REPLY
Readonly. The last line of the last reply sent by the server.
This can still be read after the connection is closed, and is not
changed when the current session changes.
ZFTP_SESSION
Readonly. The name of the current FTP session; see the
description of the session subcommand.
ZFTP_PREFS
A string of preferences for altering aspects of zftp's behaviour.
Each preference is a single character. The following are defined:
P
Passive: attempt to make the remote server initiate data
transfers. This is slightly more efficient than sendport
mode. If the letter S occurs later in the string, zftp will
use sendport mode if passive mode is not available.
S
Sendport: initiate transfers by the FTP PORT command. If
this occurs before any P in the string, passive mode will
never be attempted.
D
Dumb: use only the bare minimum of FTP commands. This
prevents the variables ZFTP_SYSTEM and ZFTP_PWD from being
set, and will mean all connections default to ASCII type. It
may prevent ZFTP_SIZE from being set during a transfer if the
server does not send it anyway (many servers do).
If ZFTP_PREFS is not set when zftp is loaded, it will be set to a
default of `PS', i.e. use passive mode if available, otherwise
fall back to sendport mode.
ZFTP_VERBOSE
A string of digits between 0 and 5 inclusive, specifying which
responses from the server should be printed. All responses go to
standard error. If any of the numbers 1 to 5 appear in the string,
raw responses from the server with reply codes beginning with that
digit will be printed to standard error. The first digit of the
three digit reply code is defined by RFC959 to correspond to:
1.
A positive preliminary reply.
2.
A positive completion reply.
3.
A positive intermediate reply.
4.
A transient negative completion reply.
5.
A permanent negative completion reply.
It should be noted that, for unknown reasons, the reply `Service
not available', which forces termination of a connection, is
classified as 421, i.e. `transient negative', an interesting
interpretation of the word `transient'.
The code 0 is special: it indicates that all but the last line of
multiline replies read from the server will be printed to standard
error in a processed format. By convention, servers use this
mechanism for sending information for the user to read. The
appropriate reply code, if it matches the same response, takes
priority.
If ZFTP_VERBOSE is not set when zftp is loaded, it will be set to
the default value 450, i.e., messages destined for the user and
all errors will be printed. A null string is valid and specifies
that no messages should be printed.
Functions
---------
zftp_chpwd
If this function is set by the user, it is called every time the
directory changes on the server, including when a user is logged
in, or when a connection is closed. In the last case, $ZFTP_PWD
will be unset; otherwise it will reflect the new directory.
zftp_progress
If this function is set by the user, it will be called during a
get, put or append operation each time sufficient data has been
received from the host. During a get, the data is sent to
standard output, so it is vital that this function should write to
standard error or directly to the terminal, _not_ to standard
output.
When it is called with a transfer in progress, the following
additional shell parameters are set:
ZFTP_FILE
The name of the remote file being transferred from or to.
ZFTP_TRANSFER
A G for a get operation and a P for a put operation.
ZFTP_SIZE
The total size of the complete file being transferred: the
same as the first value provided by the remote and local
subcommands for a particular file. If the server cannot
supply this value for a remote file being retrieved, it will
not be set. If input is from a pipe the value may be
incorrect and correspond simply to a full pipe buffer.
ZFTP_COUNT
The amount of data so far transferred; a number between zero
and $ZFTP_SIZE, if that is set. This number is always
available.
The function is initially called with ZFTP_TRANSFER set
appropriately and ZFTP_COUNT set to zero. After the transfer is
finished, the function will be called one more time with
ZFTP_TRANSFER set to GF or PF, in case it wishes to tidy up. It
is otherwise never called twice with the same value of ZFTP_COUNT.
Sometimes the progress meter may cause disruption. It is up to the
user to decide whether the function should be defined and to use
unfunction when necessary.
Problems
--------
A connection may not be opened in the left hand side of a pipe as this
occurs in a subshell and the file information is not updated in the main
shell. In the case of type or mode changes or closing the connection
in a subshell, the information is returned but variables are not
updated until the next call to zftp. Other status changes in subshells
will not be reflected by changes to the variables (but should be
otherwise harmless).
Deleting sessions while a zftp command is active in the background can
have unexpected effects, even if it does not use the session being
deleted. This is because all shell subprocesses share information on
the state of all connections, and deleting a session changes the
ordering of that information.
On some operating systems, the control connection is not valid after a
fork(), so that operations in subshells, on the left hand side of a
pipeline, or in the background are not possible, as they should be.
This is presumably a bug in the operating system.
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