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 RFC 959). 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 mode option for open/[1,2,3] where this default behavior may be changed. Also the mode option replaces the API function force_active/1 that now has become deprecated. (force_active/1 is removed from the documentation but is still available in the code for now.)

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.

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

account(Pid, Account) -> ok | {error, Reason}

Types

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 [, RemoteFile]) -> ok | {error, Reason}

Types

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}

Types

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}

Types

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 neccessery to to call append_chunk_end to get the proper reason.

append_chunk_start(Pid, File) -> ok | {error, Reason}

Types

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}

Types

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}

Types

Pid = pid()

Dir = string()

Reason = restriction_reason() | common_reason()

Changes the working directory at the remote server to Dir.

close(Pid) -> ok

Types

Pid = pid()

Ends the ftp session.

delete(Pid, File) -> ok | {error, Reason}

Types

Pid = pid()

File = string()

Reason = restriction_reason() | common_reason()

Deletes the file File at the remote server.

formaterror(Tag) -> string()

Types

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}

Types

Pid = pid()

Dir = string()

Reason = restriction_reason()

Changes the working directory to Dir for the local client.

lpwd(Pid) -> {ok, Dir}

Types

Pid = pid()

Returns the current working directory at the local client.

ls(Pid [, Dir]) -> {ok, Listing} | {error, Reason}

Types

Pid = pid()

Dir = string()

Listing = string()

Reason = restriction_reason() | common_reason()

Returns a listing of the contents of the remote current directory (ls/1) or the specified directory (ls/2). 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}

Types

Pid = pid()

Dir = string()

Reason = restriction_reason() | common_reason()

Creates the directory Dir at the remote server.

nlist(Pid [, Dir]) -> {ok, Listing} | {error, Reason}

Types

Pid = pid()

Dir = string()

Listing = string()

Reason = restriction_reason() | common_reason()

Returns a listing of the contents of the remote current directory (nlist/1) or the specified directory (nlist/2). 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 [, Port] [, Flags]) -> {ok, Pid} | {error, Reason}

open({option_list, Option_list}) -> {ok, Pid} | {error, Reason}

Types

Host = string() | ip_address()

ip_address() = {byte(), byte(), byte(), byte()} {byte(), byte(), byte(), byte(), byte(), byte(), byte(), byte()}

byte() = 0 | 1 | ... | 255

Port = integer()

Flags = [Flag]

Flag = verbose | debug | ip_v6_disabled

Pid = pid()

Reason = ehost

Option_list = [Options]

Options = {host, Host} | {port, Port} | {mode, Mode} | {flags, Flags} | {timeout, Timeout} | {progress, ProgressOption}

Mode = active | passive

Timeout = integer()

ProgressOption = ignore | {CBModule, CBFunction, InitProgress}

CallBackModule = atom()

CallBackFunction = atom()

InitProgress = term()

Opens a session with the ftp server at Host. The argument Host is either the name of the host, its IP address in dotted decimal notation (e.g. "150.236.14.136"), or a tuple of arity 4 (ipv4) or 8 (ipv6) (ex: {150, 236, 14, 136}).

If Port is supplied, a connection is attempted using this port number instead of the default (21).

Default value for Mode is passive.

If the atom verbose is included in Flags, response messages from the remote server will be written to standard output.

The progress option is intended to be used by applications that want 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.

*

Every time a chunk of bytes is transfered the following call will be made:

*

At the end of the file the following call will be made to indicate the end of the transfer.

CBModule:CBFunction(InitProgress, File, {file_size, FileSize})

 CBModule:CBFunction(UserProgressTerm, File, {transfer_size, TransferSize})

 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:

Note:

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 or send_chunk_end/1, before a call to send_chunk_start/2; or a call has been made to another transfer function during chunk sending, i.e. before a call to send_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].

file, filename, J. Postel and J. Reynolds: File Transfer Protocol (RFC 959).

Peter Högfeldt - support@erlang.ericsson.se
Ingela Anderton Andin - support@erlang.ericsson.se