ftp

MODULE

ftp

MODULE SUMMARY

A File Transfer Protocol client

DESCRIPTION

The ftp module implements a client for file transfer according to a subset of the File Transfer Protocol (see RFC 959).

The following is a simple example of an ftp session, where the user guest with password password logs on to the remote host erlang.org, and where the file appl.erl is transferred from the remote to the local host. When the session is opened, the current directory at the remote host is /home/guest, and /home/fred at the local host. Before transferring the file, the current local directory is changed to /home/eproj/examples, and the remote directory is set to /home/guest/appl/examples.

1> {ok, Pid} = ftp:open("erlang.org").
{ok,<0.22.0>}
2> ftp:user(Pid, "guest", "password").
ok
3> ftp:pwd(Pid).
{ok, "/home/guest"}
4> ftp:cd(Pid, "appl/examples").
ok
5> ftp:lpwd(Pid).
{ok, "/home/fred"}.
6> ftp:lcd(Pid, "/home/eproj/examples").
ok
7> ftp:recv(Pid, "appl.erl").
ok
8> ftp:close(Pid).
ok
    

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 contiguous parts of a file to be stored in a remote file (see send_chunk_start/2, send_chunk/2 and send_chunk_end/1).

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.

EXPORTS

cd(Pid, Dir) -> ok | {error, Reason}

Types:
Pid = pid()
Dir = string()
Reason = epath | elogin | econn

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 = epath | elogin | econn

Deletes the file File at the remote server.

formaterror(Tag) -> string()

Types:
Tag = {error, atom()} | atom()

Given an error return value {error, Reason}, this function returns a readable string describing the error.

lcd(Pid, Dir) -> ok | {error, Reason}

Types:
Pid = pid()
Dir = string()
Reason = epath

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 = epath | elogin | econn

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 = epath | elogin | econn

Creates the directory Dir at the remote server.

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

Types:
Pid = pid()
Dir = string()
Listing = string()
Reason = epath | elogin | econn

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

Types:
Host = string() | ip_address()
ip_address() = {byte(), byte(), byte(), byte()}
byte() = 0 | 1 | ... | 255
Flags = [Flag]
Flag = verbose
Pid = pid()
Reason = ehost

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 (e.g. {150, 236, 14, 136}).

If Flags is set, response messages from the remote server will be written to standard output.

The file transfer type is set to binary when the session is opened.

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. The ftp client process is linked to the caller.

pwd(Pid) -> {ok, Dir} | {error, Reason}

Types:
Pid = pid()
Reason = elogin | econn

Returns the current working directory at the remote server.

recv(Pid, RemoteFile [, LocalFile]) -> ok | {error, Reason}

Types:
Pid = pid()
RemoteFile = LocalFile = string()
Reason = epath | elogin | econn

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.

recv_bin(Pid, RemoteFile) -> {ok, Bin} | {error, Reason}

Types:
Pid = pid()
Bin = binary()
RemoteFile = string()
Reason = epath | elogin | econn

Transfers the file RemoteFile from the remote server and receives it as a binary.

rename(Pid, Old, New) -> ok | {error, Reason}

Types:
Pid = pid()
CurrFile = NewFile = string()
Reason = epath | elogin | econn

Renames Old to New at the remote server.

rmdir(Pid, Dir) -> ok | {error, Reason}

Types:
Pid = pid()
Dir = string()
Reason = epath | elogin | econn

Removes directory Dir at the remote server.

send(Pid, LocalFile [, RemoteFile]) -> ok | {error, Reason}

Types:
Pid = pid()
LocalFile = RemoteFile = string()
Reason = epath | elogin | econn | etnospc | epnospc | efnamena

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}

Types:
Pid = pid()
Bin = binary()()
RemoteFile = string()
Reason = epath | elogin | enotbinary | econn | etnospc | epnospc | efnamena

Transfers the binary Bin into the file RemoteFile at the remote server.

send_chunk(Pid, Bin) -> ok | {error, Reason}

Types:
Pid = pid()
Bin = binary()
Reason = elogin | echunk | enotbinary | econn

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 neccessery to to call send_chunk_end to get the proper reason.

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

Types:
Pid = pid()
File = string()
Reason = epath | elogin | econn

Start transfer of chunks into the file File at the remote server.

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

Types:
Pid = pid()
Reason = elogin | echunk | econn | etnospc | epnospc | efnamena

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}

Types:
Pid = pid()
Type = ascii | binary
Reason = etype | elogin | econn

Sets the file transfer type to ascii or binary. When an ftp session is opened, the transfer type is set to binary.

user(Pid, User, Password) -> ok | {error, Reason}

Types:
Pid = pid()
User = Password = string()
Reason = euser | econn

Performs login of User with Password.

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 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].

SEE ALSO

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

AUTHORS

Peter Högfeldt - support@erlang.ericsson.se