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NAME

       ftp - 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 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 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(3erl) 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 = non_neg_integer()

           Connection timeout.

           Default is 60000 (milliseconds).

         {dtimeout, DTimeout}:

           DTimeout = non_neg_integer() | infinity

           Data  Connect  timeout. The time the client will wait 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.

       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.

EXPORTS

       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) ->
       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  necessary  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 an ftp session, created using the open function.

       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) ->
       ls(Pid, Pathname) -> {ok, Listing} | {error, Reason}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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()} | {tls,
                 tls_options()} | {timeout, timeout()}  |  {dtimeout,  dtimeout()}  |  {progress,
                 progress()}
                 ipfamily() = inet | inet6 | inet6fb4 (defaults to inet)
                 port() = integer() > 0 (defaults to 21)
                 mode() = active | passive (defaults to passive)
                 tls_options() = [ssl:ssloption()]
                 timeout() = integer() > 0 (defaults to 60000 milliseconds)
                 dtimeout() = integer() > 0 | infinity (defaults to infinity)
                 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.

              If the option {tls, tls_options()} is present, the ftp session will be  transported
              over  tls  (ftps,  see RFC 4217). The list tls_options() may 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 the close function.

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

              Types:

                 Pid = pid()
                 Reason = restriction_reason() | common_reason()

              Returns the current working directory at the remote server.

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

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 Pid = pid()
                 CurrFile = NewFile = string()
                 Reason = restriction_reason() | common_reason()

              Renames Old to New at the remote server.

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

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 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}

              Types:

                 Pid = pid()
                 User = Password = string()
                 Reason = euser | common_reason()

              Performs login of User with Password.

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

              Types:

                 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]

              Types:

                 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  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).