ssh_sftp(3)

NAME
ssh_sftp - SFTP client.

DESCRIPTION

This module implements an SSH FTP (SFTP) client. SFTP is a secure, encrypted file transfer service available for SSH.

DATA TYPES

chunk_size() :: undefined | pos_integer().
crypto_fun() :: fun((TextIn :: binary(), crypto_state()) -> crypto_result()).
crypto_result() :: {ok, TextOut :: binary(), crypto_state()} | {ok, TextOut :: binary(), crypto_state(), chunk_size()}.

    The initial crypto_state/0 returned from the init_fun/0 is folded into repeated applications of the crypto_fun/0 in the tar_crypto_spec. The binary returned from that fun is sent to the remote SFTP server and the new crypto_state/0 is used in the next call of the crypto_fun/0.

    If the crypto_fun/0 reurns a chunk_size/0, that value is as block size for further blocks in calls to crypto_fun/0.
crypto_state() :: any().

    The init_fun/0 in the tar_crypto_spec is applied once prior to any other crypto operation. The intention is that this function initiates the encryption or decryption for example by calling crypto:crypto_init/4 or similar. The crypto_state/0 is the state such a function may return.

    If the selected cipher needs to have the input data partitioned into blocks of a certain size, the init_fun/0 should return the second form of return value with the chunk_size/0 set to the block size. If the chunk_size/0 is undefined, the size of the PlainBins varies, because this is intended for stream crypto, whereas a fixed chunk_size/0 is intended for block crypto. A chunk_size/0 can be changed in the return from the crypto_fun/0. The value can be changed between pos_integer/0 and undefined.
decrypt_spec() :: {init_fun(), crypto_fun()}.

    Specifies the encryption or decryption applied to tar files when using open_tar/3 or open_tar/4.

    The encryption or decryption is applied to the generated stream of bytes prior to sending the resulting stream to the SFTP server.

    For code examples see Section Example with encryption in the ssh Users Guide.
encrypt_spec() :: {init_fun(), crypto_fun(), final_fun()}.
final_fun() :: fun((FinalTextIn :: binary(), crypto_state()) -> {ok, FinalTextOut :: binary()}).

    If doing encryption, the final_fun/0 in the tar_crypto_spec is applied to the last piece of data. The final_fun/0 is responsible for padding (if needed) and encryption of that last piece.
init_fun() :: fun(() -> {ok, crypto_state()}) | fun(() -> {ok, crypto_state(), chunk_size()}).
reason() :: atom() | string() | tuple().

    A description of the reason why an operation failed.

    The atom/0 value is formed from the sftp error codes in the protocol-level responses as defined in draft-ietf-secsh-filexfer-13 section 9.1. The codes are named as SSH_FX_* which are transformed into lowercase of the star-part. E.g. the error code SSH_FX_NO_SUCH_FILE will cause the reason/0 to be no_such_file.

    The string/0 reason is the error information from the server in case of an exit-signal. If that information is empty, the reason is the exit signal name.

    The tuple/0 reason are other errors like for example {exit_status,1}.
sftp_option() :: {timeout, timeout()} | {sftp_vsn, pos_integer()} | {window_size, pos_integer()} | {packet_size, pos_integer()}.

    Specifies available SFTP options.
tar_crypto_spec() :: encrypt_spec() | decrypt_spec().

FUNCTIONS

apread(ChannelPid, Handle, Position, Len) -> {async, N} | Error when ChannelPid :: pid(), Handle :: term(), Position :: integer(), Len :: integer(), Error :: {error, reason()}, N :: term().

    The apread/4 function reads from a specified position, combining the position/3 and aread/3 functions.
apwrite(ChannelPid, Handle, Position, Data) -> {async, N} | Error when ChannelPid :: pid(), Handle :: term(), Position :: integer(), Data :: binary(), Error :: {error, reason()}, N :: term().

    The apwrite/4 function writes to a specified position, combining the position/3 and awrite/3 functions.
aread(ChannelPid, Handle, Len) -> {async, N} | Error when ChannelPid :: pid(), Handle :: term(), Len :: integer(), Error :: {error, reason()}, N :: term().

    Reads from an open file, without waiting for the result. If the handle is valid, the function returns {async, N}, where N is a term guaranteed to be unique between calls of aread. The actual data is sent as a message to the calling process. This message has the form {async_reply, N, Result}, where Result is the result from the read, either {ok, Data}, eof, or {error, reason()}.
awrite(ChannelPid, Handle, Data) -> {async, N} | Error when ChannelPid :: pid(), Handle :: term(), Data :: binary(), Error :: {error, reason()}, N :: term().

    Writes to an open file, without waiting for the result. If the handle is valid, the function returns {async, N}, where N is a term guaranteed to be unique between calls of awrite. The result of the write operation is sent as a message to the calling process. This message has the form {async_reply, N, Result}, where Result is the result from the write, either ok, or {error, reason()}.
close(ChannelPid, Handle, Timeout) -> ok | Error when ChannelPid :: pid(), Handle :: term(), Timeout :: timeout(), Error :: {error, reason()}.

    Closes a handle to an open file or directory on the server.
del_dir(ChannelPid, Name, Timeout) -> ok | Error when ChannelPid :: pid(), Name :: string(), Timeout :: timeout(), Error :: {error, reason()}.

    Deletes a directory specified by Name. The directory must be empty before it can be successfully deleted.
delete(ChannelPid, Name, Timeout) -> ok | Error when ChannelPid :: pid(), Name :: string(), Timeout :: timeout(), Error :: {error, reason()}.

    Deletes the file specified by Name.
list_dir(ChannelPid, Path, Timeout) -> {ok, FileNames} | Error when ChannelPid :: pid(), Path :: string(), Timeout :: timeout(), FileNames :: [FileName], FileName :: string(), Error :: {error, reason()}.

    Lists the given directory on the server, returning the filenames as a list of strings.
make_dir(ChannelPid, Name, Timeout) -> ok | Error when ChannelPid :: pid(), Name :: string(), Timeout :: timeout(), Error :: {error, reason()}.

    Creates a directory specified by Name. Name must be a full path to a new directory. The directory can only be created in an existing directory.
make_symlink(ChannelPid, Name, Target, Timeout) -> ok | Error when ChannelPid :: pid(), Name :: string(), Target :: string(), Timeout :: timeout(), Error :: {error, reason()}.

    Creates a symbolic link pointing to Target with the name Name.
open(ChannelPid, Name, Mode, Timeout) -> {ok, Handle} | Error when ChannelPid :: pid(), Name :: string(), Mode :: [read | write | append | binary | raw], Timeout :: timeout(), Handle :: term(), Error :: {error, reason()}.

    Opens a file on the server and returns a handle, which can be used for reading or writing.
open_tar(ChannelPid, Path, Mode, Timeout) -> {ok, Handle} | Error when ChannelPid :: pid(), Path :: string(), Mode :: [read | write | {crypto, tar_crypto_spec()}], Timeout :: timeout(), Handle :: term(), Error :: {error, reason()}.

    Opens a handle to a tar file on the server, associated with ChannelPid. The handle can be used for remote tar creation and extraction. The actual writing and reading is performed by calls to erl_tar:add/3,4 and erl_tar:extract/2. Note: The erl_tar:init/3 function should not be called, that one is called by this open_tar function.

    For code examples see Section SFTP Client with TAR Compression in the ssh Users Guide.

    The crypto mode option is explained in the data types section above, see Crypto operations for open_tar. Encryption is assumed if the Mode contains write, and decryption if the Mode contains read.
opendir(ChannelPid, Path, Timeout) -> {ok, Handle} | Error when ChannelPid :: pid(), Path :: string(), Timeout :: timeout(), Handle :: term(), Error :: {error, reason()}.

    Opens a handle to a directory on the server. The handle can be used for reading directory contents.
position(ChannelPid, Handle, Location, Timeout) -> {ok, NewPosition} | Error when ChannelPid :: pid(), Handle :: term(), Location :: Offset | {bof, Offset} | {cur, Offset} | {eof, Offset} | bof | cur | eof, Timeout :: timeout(), Offset :: integer(), NewPosition :: integer(), Error :: {error, reason()}.

    Sets the file position of the file referenced by Handle. Returns {ok, NewPosition} (as an absolute offset) if successful, otherwise {error, reason()}. Location is one of the following: Offset
        The same as {bof, Offset}.
    {bof, Offset}
        Absolute offset.
    {cur, Offset}
        Offset from the current position.
    {eof, Offset}
        Offset from the end of file.
    bof | cur | eof
        The same as eariler with Offset 0, that is, {bof, 0} | {cur, 0} | {eof, 0}.
pread(ChannelPid, Handle, Position, Len, Timeout) -> {ok, Data} | eof | Error when ChannelPid :: pid(), Handle :: term(), Position :: integer(), Len :: integer(), Timeout :: timeout(), Data :: string() | binary(), Error :: {error, reason()}.

    The pread/3,4 function reads from a specified position, combining the position/3 and read/3,4 functions.
pwrite(ChannelPid, Handle, Position, Data, Timeout) -> ok | Error when ChannelPid :: pid(), Handle :: term(), Position :: integer(), Data :: iolist(), Timeout :: timeout(), Error :: {error, reason()}.

    The pwrite/3,4 function writes to a specified position, combining the position/3 and write/3,4 functions.
read(ChannelPid, Handle, Len, Timeout) -> {ok, Data} | eof | Error when ChannelPid :: pid(), Handle :: term(), Len :: integer(), Timeout :: timeout(), Data :: string() | binary(), Error :: {error, reason()}.

    Reads Len bytes from the file referenced by Handle. Returns {ok, Data}, eof, or {error, reason()}. If the file is opened with binary, Data is a binary, otherwise it is a string.

    If the file is read past eof, only the remaining bytes are read and returned. If no bytes are read, eof is returned.
read_file(ChannelPid, File, Timeout) -> {ok, Data} | Error when ChannelPid :: pid(), File :: string(), Data :: binary(), Timeout :: timeout(), Error :: {error, reason()}.

    Reads a file from the server, and returns the data in a binary.
read_file_info(ChannelPid, Name, Timeout) -> {ok, FileInfo} | Error when ChannelPid :: pid(), Name :: string(), Timeout :: timeout(), FileInfo :: file:file_info(), Error :: {error, reason()}.

    Returns a file_info record from the file system object specified by Name or Handle. See file:read_file_info/2 for information about the record.

    Depending on the underlying OS:es links might be followed and info on the final file, directory etc is returned. See read_link_info/2 on how to get information on links instead.
read_link(ChannelPid, Name, Timeout) -> {ok, Target} | Error when ChannelPid :: pid(), Name :: string(), Target :: string(), Timeout :: timeout(), Error :: {error, reason()}.

    Reads the link target from the symbolic link specified by name.
read_link_info(ChannelPid, Name, Timeout) -> {ok, FileInfo} | Error when ChannelPid :: pid(), Name :: string(), FileInfo :: file:file_info(), Timeout :: timeout(), Error :: {error, reason()}.

    Returns a file_info record from the symbolic link specified by Name or Handle. See file:read_link_info/2 for information about the record.
rename(ChannelPid, OldName, NewName, Timeout) -> ok | Error when ChannelPid :: pid(), OldName :: string(), NewName :: string(), Timeout :: timeout(), Error :: {error, reason()}.

    Renames a file named OldName and gives it the name NewName.
start_channel(ssh:open_socket(), [ssh:client_option() | sftp_option()]) -> {ok, pid(), ssh:connection_ref()} | {error, reason()}; (ssh:connection_ref(), [ssh:client_option() | sftp_option()]) -> {ok, pid()} | {ok, pid(), ssh:connection_ref()} | {error, reason()}; (ssh:host(), [ssh:client_option() | sftp_option()]) -> {ok, pid(), ssh:connection_ref()} | {error, reason()}.

    Starts new ssh channel for communicating with the SFTP server.

    Starts an ssh channel when first argument is a connection reference.

    Equivalent to start_channel(Host, 22, UserOptions) when first argument is recognized as network host.

    Otherwise, first argument is treated as a network socket which will be used for establishing new SSH connection. New connection reference will be used for starting an SSH channel.

    The returned pid for this process is to be used as input to all other API functions in this module.

    See also (start_channel/3).
start_channel(ssh:host(), inet:port_number(), [ssh:client_option() | sftp_option()]) -> {ok, pid(), ssh:connection_ref()} | {error, reason()}.

    Starts new ssh connection and channel for communicating with the SFTP server.

    The returned pid for this process is to be used as input to all other API functions in this module.

    Options: {timeout, timeout()}
        There are two ways to set a timeout for the underlying ssh connection:

            • If the connection timeout option connect_timeout is set, that value is used also for the negotiation timeout and this option (timeout) is ignored.

            • Otherwise, this option (timeout) is used as the negotiation timeout only and there is no connection timeout set

        The value defaults to infinity.
    {sftp_vsn, integer()}
        Desired SFTP protocol version. The actual version is the minimum of the desired version and the maximum supported versions by the SFTP server.

    All other options are directly passed to ssh:connect/3 or ignored if a connection is already provided.
stop_channel(ChannelPid) -> ok when ChannelPid :: pid().

    Stops an SFTP channel. Does not close the SSH connection. Use ssh:close/1 to close it.
write(ChannelPid, Handle, Data, Timeout) -> ok | Error when ChannelPid :: pid(), Handle :: term(), Data :: iodata(), Timeout :: timeout(), Error :: {error, reason()}.

    Writes data to the file referenced by Handle. The file is to be opened with write or append flag. Returns ok if successful or {error, reason()} otherwise.
write_file(ChannelPid, File, Data, Timeout) -> ok | Error when ChannelPid :: pid(), File :: string(), Data :: iodata(), Timeout :: timeout(), Error :: {error, reason()}.

    Writes a file to the server. The file is created if it does not exist but overwritten if it exists.
write_file_info(ChannelPid, Name, FileInfo, Timeout) -> ok | Error when ChannelPid :: pid(), Name :: string(), FileInfo :: file:file_info(), Timeout :: timeout(), Error :: {error, reason()}.

    Writes file information from a file_info record to the file specified by Name. See file:write_file_info/2,3 for information about the record.