ftp
A File Transfer Protocol client
The ftp
module implements a client for file transfer
according to a subset of the File Transfer Protocol (see RFC959).
Starting from inets version 4.4.1 the ftp client will always try to use passive ftp mode and only resort to active ftp mode if this fails. There is a start option mode where this default behavior may be changed.
There are two ways to start an ftp client. One is using the Inets service framework and the other is to start it directy as a standalone process using the open function.
For a simple example of an ftp session see Inets User's Guide.
In addition to the ordinary functions for receiving and sending
files (see recv/2
, recv/3
, send/2
and
send/3
) there are functions for receiving remote files as
binaries (see recv_bin/2
) and for sending binaries to to be
stored as remote files (see send_bin/3
).
There is also a set of functions for sending and receiving
contiguous parts of a file to be stored in a remote file (for send
see send_chunk_start/2
, send_chunk/2
and
send_chunk_end/1
and for receive see
recv_chunk_start/2
and recv_chunk/
).
The particular return values of the functions below depend very
much on the implementation of the FTP server at the remote
host. In particular the results from ls
and nlist
varies. Often real errors are not reported as errors by ls
,
even if for instance a file or directory does not
exist. nlist
is usually more strict, but some
implementations have the peculiar behaviour of responding with an
error, if the request is a listing of the contents of directory
which exists but is empty.
FTP CLIENT SERVICE START/STOP
The FTP client can be started and stopped dynamically in runtime by
calling the Inets application API
inets:start(ftpc, ServiceConfig)
,
or inets:start(ftpc, ServiceConfig, How)
, and
inets:stop(ftpc, Pid)
.
See inets(3) for more info.
Below follows a description of the available configuration options.
- {host, Host}
-
Host =
string() | ip_address()
- {port, Port}
-
Port =
integer() > 0
Default is 21.
- {mode, Mode}
-
Mode =
>active | passive
Default is
passive
. - {verbose, Verbose}
-
Verbose =
boolean()
This determines if the FTP communication should be verbose or not.
Default is
false
. - {debug, Debug}
-
Debug =
trace | debug | disable
Debugging using the dbg toolkit.
Default is
disable
. - {ipfamily, IpFamily}
-
IpFamily =
inet | inet6 | inet6fb4
With
inet6fb4
the client behaves as before (it tries to use IPv6 and only if that does not work, it uses IPv4).Default is
inet
(IPv4). - {timeout, Timeout}
-
Timeout =
integer() >= 0
Connection timeout.
Default is 60000 (milliseconds).
- {progress, Progress}
-
Progress =
ignore | {CBModule, CBFunction, InitProgress}
CBModule =
atom()
, CBFunction =atom()
InitProgress =
term()
Default is
ignore
.
The progress option is intended to be used by applications that want to create some type of progress report such as a progress bar in a GUI. The default value for the progress option is ignore e.i. the option is not used. When the progress option is specified the following will happen when ftp:send/[3,4] or ftp:recv/[3,4] are called.
-
Before a file is transfered the following call will be made to indicate the start of the file transfer and how big the file is. The return value of the callback function should be a new value for the UserProgressTerm that will bu used as input next time the callback function is called.
CBModule:CBFunction(InitProgress, File, {file_size, FileSize})
-
Every time a chunk of bytes is transfered the following call will be made:
CBModule:CBFunction(UserProgressTerm, File, {transfer_size, TransferSize})
-
At the end of the file the following call will be made to indicate the end of the transfer.
CBModule:CBFunction(UserProgressTerm, File, {transfer_size, 0})
The callback function should be defined as
CBModule:CBFunction(UserProgressTerm, File, Size) -> UserProgressTerm
CBModule = CBFunction = atom()
UserProgressTerm = term()
File = string()
Size = {transfer_size, integer()} | {file_size, integer()} | {file_size, unknown}
Alas for remote files it is not possible for ftp to determine the
file size in a platform independent way. In this case the size
will be unknown
and it is left to the application to find
out the size.
Note!
The callback is made by a middleman process, hence the file transfer will not be affected by the code in the progress callback function. If the callback should crash this will be detected by the ftp connection process that will print an info-report and then go one as if the progress option was set to ignore.
The file transfer type is set to the default of the FTP server when the session is opened. This is usually ASCCI-mode.
The current local working directory (cf. lpwd/1
) is set to
the value reported by file:get_cwd/1
. the wanted
local directory.
The return value Pid
is used as a reference to the
newly created ftp client in all other functions, and they should
be called by the process that created the connection. The ftp
client process monitors the process that created it and
will terminate if that process terminates.
COMMON DATA TYPES
Here follows type definitions that are used by more than one function in the FTP client API.
pid() - identifier of an ftp connection.
string() = list of ASCII characters.
shortage_reason() = etnospc | epnospc
restriction_reason() = epath | efnamena | elogin | enotbinary
- note not all restrictions may always relevant to all functions
common_reason() = econn | eclosed | term() - some kind of
explanation of what went wrong.
Functions
account(Pid, Account) -> ok | {error, Reason}
Pid = pid()
Account = string()
Reason = eacct | common_reason()
If an account is needed for an operation set the account with this operation.
append(Pid, LocalFile) ->
append(Pid, LocalFile, RemoteFile) -> ok | {error, Reason}
Pid = pid()
LocalFile = RemoteFile = string()
Reason = epath | elogin | etnospc | epnospc | efnamena | common_reason
Transfers the file LocalFile
to the remote server. If
RemoteFile
is specified, the name of the remote file that the
file will be appended to is set to RemoteFile
; otherwise
the name is set to LocalFile
If the file does not exists the
file will be created.
append_bin(Pid, Bin, RemoteFile) -> ok | {error, Reason}
Pid = pid()
Bin = binary()()
RemoteFile = string()
Reason = restriction_reason()| shortage_reason() | common_reason()
Transfers the binary Bin
to the remote server and append
it to the file RemoteFile
. If the file does not exists it
will be created.
append_chunk(Pid, Bin) -> ok | {error, Reason}
Pid = pid()
Bin = binary()
Reason = echunk | restriction_reason() | common_reason()
Transfer the chunk Bin
to the remote server, which
append it into the file specified in the call to
append_chunk_start/2
.
Note that for some errors, e.g. file system full, it is
necessary to to call append_chunk_end
to get the
proper reason.
append_chunk_start(Pid, File) -> ok | {error, Reason}
Pid = pid()
File = string()
Reason = restriction_reason() | common_reason()
Start the transfer of chunks for appending to the file
File
at the remote server. If the file does not exists
it will be created.
append_chunk_end(Pid) -> ok | {error, Reason}
Pid = pid()
Reason = echunk | restriction_reason() | shortage_reason()
Stops transfer of chunks for appending to the remote server.
The file at the remote server, specified in the call to
append_chunk_start/2
is closed by the server.
cd(Pid, Dir) -> ok | {error, Reason}
Pid = pid()
Dir = string()
Reason = restriction_reason() | common_reason()
Changes the working directory at the remote server to
Dir
.
delete(Pid, File) -> ok | {error, Reason}
Pid = pid()
File = string()
Reason = restriction_reason() | common_reason()
Deletes the file File
at the remote server.
formaterror(Tag) -> string()
Tag = {error, atom()} | atom()
Given an error return value {error, AtomReason}
,
this function returns a readable string describing the error.
lcd(Pid, Dir) -> ok | {error, Reason}
Pid = pid()
Dir = string()
Reason = restriction_reason()
Changes the working directory to Dir
for the local client.
lpwd(Pid) -> {ok, Dir}
Pid = pid()
Returns the current working directory at the local client.
ls(Pid) ->
ls(Pid, Pathname) -> {ok, Listing} | {error, Reason}
Pid = pid()
Pathname = string()
Listing = string()
Reason = restriction_reason() | common_reason()
Returns a list of files in long format.
Pathname
can be a directory, a group of files or
even a file. The Pathname
string can contain wildcard(s).
ls/1
implies the user's current remote directory.
The format of Listing
is operating system dependent
(on UNIX it is typically produced from the output of the
ls -l
shell command).
mkdir(Pid, Dir) -> ok | {error, Reason}
Pid = pid()
Dir = string()
Reason = restriction_reason() | common_reason()
Creates the directory Dir
at the remote server.
nlist(Pid) ->
nlist(Pid, Pathname) -> {ok, Listing} | {error, Reason}
Pid = pid()
Pathname = string()
Listing = string()
Reason = restriction_reason() | common_reason()
Returns a list of files in short format.
Pathname
can be a directory, a group of files or
even a file. The Pathname
string can contain wildcard(s).
nlist/1
implies the user's current remote directory.
The format of Listing
is a stream of
file names, where each name is separated by <CRLF> or
<NL>. Contrary to the ls
function, the purpose of
nlist
is to make it possible for a program to
automatically process file name information.
open(Host) -> {ok, Pid} | {error, Reason}
open(Host, Opts) -> {ok, Pid} | {error, Reason}
Host = string() | ip_address()
Opts = options()
options() = [option()]
option() = start_option() | open_option()
start_option() = {verbose, verbose()} | {debug, debug()}
verbose() = boolean() (defaults to false)
debug() = disable | debug | trace (defaults to disable)
open_option() = {ipfamily, ipfamily()} | {port, port()} | {mode, mode()} | {timeout, timeout()} | {progress, progress()}
ipfamily() = inet | inet6 | inet6fb4 (defaults to inet)
port() = integer() > 0 (defaults to 21)
mode() = active | passive (defaults to passive)
timeout() = integer() >= 0 (defaults to 60000 milliseconds)
pogress() = ignore | {module(), function(), initial_data()} (defaults to ignore)
module() = atom()
function() = atom()
initial_data() = term()
Reason = ehost | term()
This function is used to start a standalone ftp client process
(without the inets service framework) and
open a session with the FTP server at Host
.
A session opened in this way, is closed using the close function.
pwd(Pid) -> {ok, Dir} | {error, Reason}
Pid = pid()
Reason = restriction_reason() | common_reason()
Returns the current working directory at the remote server.
pwd(Pid) -> {ok, Dir} | {error, Reason}
Pid = pid()
Reason = restriction_reason() | common_reason()
Returns the current working directory at the remote server.
recv(Pid, RemoteFile) ->
recv(Pid, RemoteFile, LocalFile) -> ok | {error, Reason}
Pid = pid()
RemoteFile = LocalFile = string()
Reason = restriction_reason() | common_reason() | file_write_error_reason()
file_write_error_reason() = see file:write/2
Transfer the file RemoteFile
from the remote server
to the the file system of the local client. If
LocalFile
is specified, the local file will be
LocalFile
; otherwise it will be
RemoteFile
.
If the file write fails
(e.g. enospc), then the command is aborted and {error, file_write_error_reason()}
is returned. The file is
however not removed.
recv_bin(Pid, RemoteFile) -> {ok, Bin} | {error, Reason}
Pid = pid()
Bin = binary()
RemoteFile = string()
Reason = restriction_reason() | common_reason()
Transfers the file RemoteFile
from the remote server and
receives it as a binary.
recv_chunk_start(Pid, RemoteFile) -> ok | {error, Reason}
Pid = pid()
RemoteFile = string()
Reason = restriction_reason() | common_reason()
Start transfer of the file RemoteFile
from the
remote server.
recv_chunk(Pid) -> ok | {ok, Bin} | {error, Reason}
Pid = pid()
Bin = binary()
Reason = restriction_reason() | common_reason()
Receive a chunk of the remote file (RemoteFile
of
recv_chunk_start
). The return values has the following
meaning:
ok
the transfer is complete.{ok, Bin}
just another chunk of the file.{error, Reason}
transfer failed.
rename(Pid, Old, New) -> ok | {error, Reason}
Pid = pid()
CurrFile = NewFile = string()
Reason = restriction_reason() | common_reason()
Renames Old
to New
at the remote server.
rmdir(Pid, Dir) -> ok | {error, Reason}
Pid = pid()
Dir = string()
Reason = restriction_reason() | common_reason()
Removes directory Dir
at the remote server.
send(Pid, LocalFile) ->
send(Pid, LocalFile, RemoteFile) -> ok | {error, Reason}
Pid = pid()
LocalFile = RemoteFile = string()
Reason = restriction_reason() | common_reason() | shortage_reason()
Transfers the file LocalFile
to the remote server. If
RemoteFile
is specified, the name of the remote file is set
to RemoteFile
; otherwise the name is set to LocalFile
.
send_bin(Pid, Bin, RemoteFile) -> ok | {error, Reason}
Pid = pid()
Bin = binary()()
RemoteFile = string()
Reason = restriction_reason() | common_reason() | shortage_reason()
Transfers the binary Bin
into the file RemoteFile
at the remote server.
send_chunk(Pid, Bin) -> ok | {error, Reason}
Pid = pid()
Bin = binary()
Reason = echunk | restriction_reason() | common_reason()
Transfer the chunk Bin
to the remote server, which
writes it into the file specified in the call to
send_chunk_start/2
.
Note that for some errors, e.g. file system full, it is
necessary to to call send_chunk_end
to get the
proper reason.
send_chunk_start(Pid, File) -> ok | {error, Reason}
Pid = pid()
File = string()
Reason = restriction_reason() | common_reason()
Start transfer of chunks into the file File
at the
remote server.
send_chunk_end(Pid) -> ok | {error, Reason}
Pid = pid()
Reason = restriction_reason() | common_reason() | shortage_reason()
Stops transfer of chunks to the remote server. The file at the
remote server, specified in the call to send_chunk_start/2
is closed by the server.
type(Pid, Type) -> ok | {error, Reason}
Pid = pid()
Type = ascii | binary
Reason = etype | restriction_reason() | common_reason()
Sets the file transfer type to ascii
or binary
. When
an ftp session is opened, the default transfer type of the
server is used, most often ascii
, which is the default
according to RFC 959.
user(Pid, User, Password) -> ok | {error, Reason}
Pid = pid()
User = Password = string()
Reason = euser | common_reason()
Performs login of User
with Password
.
user(Pid, User, Password, Account) -> ok | {error, Reason}
Pid = pid()
User = Password = string()
Reason = euser | common_reason()
Performs login of User
with Password
to the account
specified by Account
.
quote(Pid, Command) -> [FTPLine]
Pid = pid()
Command = string()
FTPLine = string() - Note the telnet end of line characters, from the ftp protocol definition, CRLF e.g. "\\r\\n" has been removed.
Sends an arbitrary FTP command and returns verbatimly a list of the lines sent back by the FTP server. This functions is intended to give an application accesses to FTP commands that are server specific or that may not be provided by this FTP client.
Note!
FTP commands that require a data connection can not be successfully issued with this function.
ERRORS
The possible error reasons and the corresponding diagnostic strings
returned by formaterror/1
are as follows:
echunk
-
Synchronisation error during chunk sending.
A call has been made to
send_chunk/2
orsend_chunk_end/1
, before a call tosend_chunk_start/2
; or a call has been made to another transfer function during chunk sending, i.e. before a call tosend_chunk_end/1
. eclosed
-
The session has been closed.
econn
-
Connection to remote server prematurely closed.
ehost
-
Host not found, FTP server not found, or connection rejected by FTP server.
elogin
-
User not logged in.
enotbinary
-
Term is not a binary.
epath
-
No such file or directory, or directory already exists, or permission denied.
etype
-
No such type.
euser
-
User name or password not valid.
etnospc
-
Insufficient storage space in system [452].
epnospc
-
Exceeded storage allocation (for current directory or dataset) [552].
efnamena
-
File name not allowed [553].
SEE ALSO
file, filename, J. Postel and J. Reynolds: File Transfer Protocol (RFC 959).
- account/2
- append/2
- append/3
- append_bin/3
- append_chunk/2
- append_chunk_start/2
- append_chunk_end/1
- cd/2
- close/1
- delete/2
- formaterror/1
- lcd/2
- lpwd/1
- ls/1
- ls/2
- mkdir/2
- nlist/1
- nlist/2
- open/1
- open/2
- pwd/1
- pwd/1-1
- recv/2
- recv/3
- recv_bin/2
- recv_chunk_start/2
- recv_chunk/1
- rename/3
- rmdir/2
- send/2
- send/3
- send_bin/3
- send_chunk/2
- send_chunk_start/2
- send_chunk_end/1
- type/2
- user/3
- user/4
- quote/2