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Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
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ftp
Peter Högfeldt
1997-11-05
B
ftp.xml
ftp
A File Transfer Protocol client.
This module implements a client for file transfer
according to a subset of the File Transfer Protocol (FTP), see
RFC 959.
The FTP client always tries to use passive FTP mode and only resort
to active FTP mode if this fails. This default behavior can be
changed by start option mode.
An FTP client can be started in two ways. One is using the
service_start function,
the other is to start it directly as a standalone process
using function open.
For a simple example of an FTP session, see
FTP 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 be
stored as remote files (see send_bin/3).
A set of functions is provvided 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. For receive, see
recv_chunk_start/2 and recv_chunk/).
The return values of the following functions depend
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 example, 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 a directory
that exists but is empty.
FTP CLIENT SERVICE START/STOP
The FTP client can be started and stopped dynamically in runtime by
calling the ftp application API
ftp:start_service(ServiceConfig) and
ftp:stop_service(Pid).
The available configuration options are as follows:
{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()
Determines if the FTP communication is to 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, that is,
tries to use IPv6, and only if that does not work it
uses IPv4).
Default is inet (IPv4).
{timeout, Timeout}
-
Timeout = non_neg_integer()
Connection time-out.
Default is 60000 (milliseconds).
{dtimeout, DTimeout}
-
DTimeout = non_neg_integer() | infinity
Data connect time-out.
The time the client waits for the server to connect to the
data socket.
Default is infinity.
{progress, Progress}
-
Progress = ignore | {CBModule, CBFunction, InitProgress}
CBModule = atom(), CBFunction = atom()
InitProgress = term()
Default is ignore.
Option progress is intended to be used by applications that
want to create some type of progress report, such as a progress bar in
a GUI. Default for the progress option is ignore,
that is, the option is not used. When the progress option is
specified, the following happens when ftp:send/[3,4] or
ftp:recv/[3,4] are called:
-
Before a file is transferred, the following call is
made to indicate the start of the file transfer and how large
the file is. The return value of the callback function
is to be a new value for the UserProgressTerm that will
be used as input the next time the callback function is
called.
CBModule:CBFunction(InitProgress, File, {file_size, FileSize})
-
Every time a chunk of bytes is transferred the
following call is made:
CBModule:CBFunction(UserProgressTerm, File, {transfer_size, TransferSize})
-
At the end of the file the following call is
made to indicate the end of the transfer:
CBModule:CBFunction(UserProgressTerm, File, {transfer_size, 0})
The callback function is to be defined as follows:
CBModule:CBFunction(UserProgressTerm, File, Size) -> UserProgressTerm
CBModule = CBFunction = atom()
UserProgressTerm = term()
File = string()
Size = {transfer_size, integer()} | {file_size, integer()} | {file_size, unknown}
For remote files, ftp cannot determine the
file size in a platform independent way. In this case the size
becomes unknown and it is left to the application to
determine the size.
The callback is made by a middleman process, hence the
file transfer is not affected by the code in the progress
callback function. If the callback crashes, this is
detected by the FTP connection process, which then prints an
info-report and goes on 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 (compare 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 are to
be called by the process that created the connection. The FTP
client process monitors the process that created it and
terminates if that process terminates.
DATA TYPES
The following type definitions 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
- all restrictions are not always relevant to all functions
common_reason() = econn | eclosed | term()
- some explanation of what went wrong
account(Pid, Account) -> ok | {error, Reason}
Specifies which account to use.
Pid = pid()
Account = string()
Reason = eacct | common_reason()
Sets the account for an operation, if needed.
append(Pid, LocalFile) ->
append(Pid, LocalFile, RemoteFile) -> ok | {error, Reason}
Transfers a file to remote server, and appends it to
Remotefile.
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 is appended to is set to RemoteFile, otherwise
to LocalFile. If the file does not exists,
it is created.
append_bin(Pid, Bin, RemoteFile) -> ok | {error, Reason}
Transfers a binary into a remote file.
Pid = pid()
Bin = binary()()
RemoteFile = string()
Reason = restriction_reason()| shortage_reason() | common_reason()
Transfers the binary Bin to the remote server and appends
it to the file RemoteFile. If the file does not exist, it
is created.
append_chunk(Pid, Bin) -> ok | {error, Reason}
Appends a chunk to the remote file.
Pid = pid()
Bin = binary()
Reason = echunk | restriction_reason() | common_reason()
Transfers the chunk Bin to the remote server, which
appends it to the file specified in the call to
append_chunk_start/2.
For some errors, for example, file system full, it is
necessary to call append_chunk_end to get the
proper reason.
append_chunk_start(Pid, File) -> ok | {error, Reason}
Starts transfer of file chunks for appending to File.
Pid = pid()
File = string()
Reason = restriction_reason() | common_reason()
Starts the transfer of chunks for appending to the file
File at the remote server. If the file does not exist,
it is created.
append_chunk_end(Pid) -> ok | {error, Reason}
Stops transfer of chunks for appending.
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}
Changes remote working directory.
Pid = pid()
Dir = string()
Reason = restriction_reason() | common_reason()
Changes the working directory at the remote server to
Dir.
close(Pid) -> ok
Ends the FTP session.
Pid = pid()
Ends an FTP session, created using function
open.
delete(Pid, File) -> ok | {error, Reason}
Deletes a file at the remote server.
Pid = pid()
File = string()
Reason = restriction_reason() | common_reason()
Deletes the file File at the remote server.
formaterror(Tag) -> string()
Returns error diagnostics.
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}
Changes local working directory.
Pid = pid()
Dir = string()
Reason = restriction_reason()
Changes the working directory to Dir for the local client.
lpwd(Pid) -> {ok, Dir}
Gets local current working directory.
Pid = pid()
Returns the current working directory at the local client.
ls(Pid) ->
ls(Pid, Pathname) -> {ok, Listing} | {error, Reason}
List of files.
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
a file. The Pathname string can contain wildcards.
ls/1 implies the current remote directory of the user.
The format of Listing depends on the operating system.
On UNIX, it is typically produced from the output of the
ls -l shell command.
mkdir(Pid, Dir) -> ok | {error, Reason}
Creates a remote directory.
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}
List of files.
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
a file. The Pathname string can contain wildcards.
nlist/1 implies the current remote directory of the user.
The format of Listing is a stream of
filenames where each filename is separated by <CRLF> or
<NL>. Contrary to function ls, the purpose of
nlist is to enable a program to
process filename information automatically.
open(Host) -> {ok, Pid} | {error, Reason}
open(Host, Opts) -> {ok, Pid} | {error, Reason}
Starts a standalone FTP client.
Host = string() | ip_address()
Opts = options()
options() = [option()]
option() = start_option() | open_option()
start_option() = {verbose, verbose()} | {debug, debug()}
verbose() = boolean() (default is false)
debug() = disable | debug | trace (default is disable)
open_option() = {ipfamily, ipfamily()} | {port, port()} | {mode, mode()} | {tls, tls_options()} | {timeout, timeout()} | {dtimeout, dtimeout()} | {progress, progress()}
ipfamily() = inet | inet6 | inet6fb4 (default is inet)
port() = integer() > 0 (default is 21)
mode() = active | passive (default is passive)
tls_options() = [ssl:ssloption()]
timeout() = integer() > 0 (default is 60000 milliseconds)
dtimeout() = integer() > 0 | infinity (default is infinity)
pogress() = ignore | {module(), function(), initial_data()} (default is ignore)
module() = atom()
function() = atom()
initial_data() = term()
Reason = ehost | term()
Starts a standalone FTP client process
(without the ftp service framework) and
opens a session with the FTP server at Host.
If option {tls, tls_options()} is present, the FTP session
is transported over tls (ftps, see
RFC 4217).
The list tls_options() can be empty. The function
ssl:connect/3
is used for securing both the control connection and the data sessions.
A session opened in this way is closed using function
close.
pwd(Pid) -> {ok, Dir} | {error, Reason}
Gets the remote current working directory.
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}
Transfers a file from remote server.
Pid = pid()
RemoteFile = LocalFile = string()
Reason = restriction_reason() | common_reason() | file_write_error_reason()
file_write_error_reason() = see file:write/2
Transfers the file RemoteFile from the remote server
to the file system of the local client. If
LocalFile is specified, the local file will be
LocalFile, otherwise
RemoteFile.
If the file write fails (for example, enospc), the command is
aborted and {error, file_write_error_reason()} is returned.
However, the file is not removed.
recv_bin(Pid, RemoteFile) -> {ok, Bin} | {error, Reason}
Transfers a file from remote server as a binary.
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}
Starts chunk-reading of the remote file.
Pid = pid()
RemoteFile = string()
Reason = restriction_reason() | common_reason()
Starts transfer of the file RemoteFile from the
remote server.
recv_chunk(Pid) -> ok | {ok, Bin} | {error, Reason}
Receives a chunk of the remote file.
Pid = pid()
Bin = binary()
Reason = restriction_reason() | common_reason()
Receives a chunk of the remote file (RemoteFile of
recv_chunk_start). The return values have 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}
Renames a file at the remote server.
Pid = pid()
CurrFile = NewFile = string()
Reason = restriction_reason() | common_reason()
Renames Old to New at the remote server.
rmdir(Pid, Dir) -> ok | {error, Reason}
Removes a remote directory.
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}
Transfers a file to the remote server.
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 to LocalFile.
send_bin(Pid, Bin, RemoteFile) -> ok | {error, Reason}
Transfers a binary into a remote file.
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}
Writes a chunk to the remote file.
Pid = pid()
Bin = binary()
Reason = echunk | restriction_reason() | common_reason()
Transfers the chunk Bin to the remote server, which
writes it into the file specified in the call to
send_chunk_start/2.
For some errors, for example, 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}
Starts transfer of file chunks.
Pid = pid()
File = string()
Reason = restriction_reason() | common_reason()
Starts transfer of chunks into the file File at the
remote server.
send_chunk_end(Pid) -> ok | {error, Reason}
Stops transfer of chunks.
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.
start_service(ServiceConfig) -> {ok, Pid} | {error, Reason}
Dynamically starts an FTP
session after the ftp application has been started.
ServiceConfig = [{Option, Value}]
Option = property()
Value = term()
Dynamically starts an FTP session after the ftp
application has been started.
As long as the ftp application is operational,
the FTP sessions are supervised and can be soft code upgraded.
stop_service(Reference) -> ok | {error, Reason}
Stops an FTP session.
Reference = pid() | term() - service-specified reference
Reason = term()
Stops a started FTP session.
type(Pid, Type) -> ok | {error, Reason}
Sets transfer type to asciior binary.
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 default
according to RFC 959.
user(Pid, User, Password) -> ok | {error, Reason}
User login.
Pid = pid()
User = Password = string()
Reason = euser | common_reason()
Performs login of User with Password.
user(Pid, User, Password, Account) -> ok | {error, Reason}
User login.
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]
Sends an arbitrary FTP command.
Pid = pid()
Command = string()
FTPLine = string(
The telnet end of line characters, from the FTP
protocol definition, CRLF, for example, "\\r\\n" has been removed.
Sends an arbitrary FTP command and returns verbatim a list
of the lines sent back by the FTP server. This function is
intended to give application accesses to FTP commands
that are server-specific or that cannot be provided by
this FTP client.
FTP commands requiring a data connection cannot be
successfully issued with this function.
ERRORS
The possible error reasons and the corresponding diagnostic strings
returned by formaterror/1 are as follows:
echunk
-
Synchronization error during chunk sending according to one
of the following:
- A call is made to send_chunk/2 or send_chunk_end/1
before a call to send_chunk_start/2.
- A call has been made to another transfer function during chunk
sending, that is, before a call to send_chunk_end/1.
eclosed
-
The session is closed.
econn
-
Connection to the remote server is prematurely closed.
ehost
-
Host is not found, FTP server is not found, or connection is rejected
by FTP server.
elogin
-
User is 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
-
Invalid username or password.
etnospc
-
Insufficient storage space in system [452].
epnospc
-
Exceeded storage allocation (for current directory or
dataset) [552].
efnamena
-
Filename not allowed [553].
SEE ALSO
file(3)
filename(3)
and J. Postel and J. Reynolds: File Transfer Protocol
(RFC 959).