View Source ssh_connection (ssh v5.2.3)
This module provides API functions to send SSH Connection Protocol events to the other side of an SSH channel.
The SSH Connection Protocol is used by clients and servers, that is, SSH channels, to communicate over the SSH connection. The API functions in this module send SSH Connection Protocol events, which are received as messages by the remote channel handling the remote channel. The Erlang format of thoose messages is (see also below):
{ssh_cm, ``t:ssh:connection_ref/0``, ``t:channel_msg/0``}
If the ssh_client_channel
behavior is used to implement the channel process,
these messages are handled by
handle_ssh_msg/2.
Summary
Types: SSH Connection Protocol: General
As mentioned in the introduction, the
SSH Connection Protocol events are
handled as messages. When writing a channel handling process without using the
support by the ssh_client_channel
behavior the process must handle thoose
messages.
Equivalent to channel_msg/0
.
Messages that include a WantReply
expect the channel handling process to call
ssh_connection:reply_request/4 with the boolean value of
WantReply
as the second argument.
Types: Data Transfer (RFC 4254, section 5.2)
Data has arrived on the channel. This event is sent as a result of calling ssh_connection:send/3,4,5.
Types: Closing a Channel (RFC 4254, section 5.3)
This event is sent as a result of calling ssh_connection:close/2.
Both the handling of this event and sending it are taken care of by the
ssh_client_channel
behavior.
Indicates that the other side sends no more data. This event is sent as a result of calling ssh_connection:send_eof/2.
Types: Requesting a Pseudo-Terminal (RFC 4254, section 6.2)
Equivalent to term_mode/0
.
A pseudo-terminal has been requested for the session. Terminal
is the value of
the TERM environment variable value, that is, vt100
. Zero dimension parameters
must be ignored. The character/row dimensions override the pixel dimensions
(when non-zero). Pixel dimensions refer to the drawable area of the window.
Opcode
in the TerminalModes
list is the mnemonic name, represented as a
lowercase Erlang atom, defined in
RFC 4254, Section 8. It can
also be an Opcode
if the mnemonic name is not listed in the RFC. Example:
OP code: 53, mnemonic name ECHO erlang atom: echo
. This event is sent as a
result of calling ssh_connection:ptty_alloc/4.
Types: Environment Variable Passing (RFC 4254, section 6.4)
Environment variables can be passed to the shell/command to be started later. This event is sent as a result of calling ssh_connection:setenv/5.
Types: Starting a Shell or Command (RFC 4254, section 6.5)
This message requests that the server starts execution of the given command. This event is sent as a result of calling ssh_connection:exec/4 .
This message requests that the user default shell is started at the other end. This event is sent as a result of calling ssh_connection:shell/2.
Types: Signals (RFC 4254, section 6.9)
A signal can be delivered to the remote process/service using the following message. Some systems do not support signals, in which case they are to ignore this message. There is currently no function to generate this event as the signals referred to are on OS-level and not something generated by an Erlang program.
Types: Returning Exit Status (RFC 4254, section 6.10)
A remote execution can terminate violently because of a signal. Then this message can be received. For details on valid string values, see RFC 4254 Section 6.10, which shows a special case of these signals.
When the command running at the other end terminates, the following message can
be sent to return the exit status of the command. A zero exit_status
usually
means that the command terminated successfully. This event is sent as a result
of calling ssh_connection:exit_status/3.
Types
The result of a call.
The status of a request. Corresponds to the SSH_MSG_CHANNEL_SUCCESS
and
SSH_MSG_CHANNEL_FAILURE
values in
RFC 4254, Section 5.4.
The valid values are 0
("normal") and 1
("stderr"), see
RFC 4254, Section 5.2.
Functions
Adjusts the SSH flow control window. This is to be done by both the client- and server-side channel processes.
A server- or client-channel process can choose to close their session by sending a close event.
Is to be called by a client-channel process to request that the server starts
executing the given command. The result is several messages according to the
following pattern. The last message is a channel close message, as the exec
request is a one-time execution that closes the channel when it is done.
Is to be called by a server-channel process to send the exit status of a command to the client.
Equivalent to ptty_alloc/4
.
Sends an SSH Connection Protocol pty_req
, to allocate a pseudo-terminal. Is to
be called by an SSH client process.
Sends status replies to requests where the requester has stated that it wants a
status report, that is, WantReply = true
. If WantReply
is false
, calling
this function becomes a "noop". Is to be called while handling an SSH Connection
Protocol message containing a WantReply
boolean value.
Equivalent to send/5
.
Equivalent to send(ConnectionRef, ChannelId, 0, Data, TimeOut) if called with TimeOut being integer.
send(ConnectionRef, ChannelId, Type, Data, TimeOut) -> ok | Error
Sends EOF on channel ChannelId
.
Equivalent to session_channel/4
.
Opens a channel for an SSH session. The channel id returned from this function is the id used as input to the other functions in this module.
Environment variables can be passed before starting the shell/command. Is to be called by a client channel processes.
Is to be called by a client channel process to request that the user default shell (typically defined in /etc/passwd in Unix systems) is executed at the server end.
Is to be called by a client-channel process for requesting to execute a predefined subsystem on the server.
Types: SSH Connection Protocol: General
-type channel_msg() :: data_ch_msg() | eof_ch_msg() | closed_ch_msg() | pty_ch_msg() | env_ch_msg() | shell_ch_msg() | exec_ch_msg() | signal_ch_msg() | window_change_ch_msg() | exit_status_ch_msg() | exit_signal_ch_msg().
As mentioned in the introduction, the
SSH Connection Protocol events are
handled as messages. When writing a channel handling process without using the
support by the ssh_client_channel
behavior the process must handle thoose
messages.
-type event() :: {ssh_cm, ssh:connection_ref(), channel_msg()}.
Equivalent to channel_msg/0
.
-type want_reply() :: boolean().
Messages that include a WantReply
expect the channel handling process to call
ssh_connection:reply_request/4 with the boolean value of
WantReply
as the second argument.
Types: Data Transfer (RFC 4254, section 5.2)
-type data_ch_msg() :: {data, ssh:channel_id(), ssh_data_type_code(), Data :: binary()}.
Data has arrived on the channel. This event is sent as a result of calling ssh_connection:send/3,4,5.
Types: Closing a Channel (RFC 4254, section 5.3)
-type closed_ch_msg() :: {closed, ssh:channel_id()}.
This event is sent as a result of calling ssh_connection:close/2.
Both the handling of this event and sending it are taken care of by the
ssh_client_channel
behavior.
-type eof_ch_msg() :: {eof, ssh:channel_id()}.
Indicates that the other side sends no more data. This event is sent as a result of calling ssh_connection:send_eof/2.
Types: Requesting a Pseudo-Terminal (RFC 4254, section 6.2)
-type pty_ch_msg() :: {pty, ssh:channel_id(), want_reply(), {Terminal :: string(), CharWidth :: non_neg_integer(), RowHeight :: non_neg_integer(), PixelWidth :: non_neg_integer(), PixelHeight :: non_neg_integer(), TerminalModes :: [term_mode()]}}.
Equivalent to term_mode/0
.
-type term_mode() :: {Opcode :: atom() | byte(), Value :: non_neg_integer()}.
A pseudo-terminal has been requested for the session. Terminal
is the value of
the TERM environment variable value, that is, vt100
. Zero dimension parameters
must be ignored. The character/row dimensions override the pixel dimensions
(when non-zero). Pixel dimensions refer to the drawable area of the window.
Opcode
in the TerminalModes
list is the mnemonic name, represented as a
lowercase Erlang atom, defined in
RFC 4254, Section 8. It can
also be an Opcode
if the mnemonic name is not listed in the RFC. Example:
OP code: 53, mnemonic name ECHO erlang atom: echo
. This event is sent as a
result of calling ssh_connection:ptty_alloc/4.
Types: Environment Variable Passing (RFC 4254, section 6.4)
-type env_ch_msg() :: {env, ssh:channel_id(), want_reply(), Var :: string(), Value :: string()}.
Environment variables can be passed to the shell/command to be started later. This event is sent as a result of calling ssh_connection:setenv/5.
Types: Starting a Shell or Command (RFC 4254, section 6.5)
-type exec_ch_msg() :: {exec, ssh:channel_id(), want_reply(), Command :: string()}.
This message requests that the server starts execution of the given command. This event is sent as a result of calling ssh_connection:exec/4 .
-type shell_ch_msg() :: {shell, ssh:channel_id(), want_reply()}.
This message requests that the user default shell is started at the other end. This event is sent as a result of calling ssh_connection:shell/2.
Types: Window Dimension Change Message (RFC 4254, section 6.7)
Types: Signals (RFC 4254, section 6.9)
-type signal_ch_msg() :: {signal, ssh:channel_id(), SignalName :: string()}.
A signal can be delivered to the remote process/service using the following message. Some systems do not support signals, in which case they are to ignore this message. There is currently no function to generate this event as the signals referred to are on OS-level and not something generated by an Erlang program.
Types: Returning Exit Status (RFC 4254, section 6.10)
-type exit_signal_ch_msg() :: {exit_signal, ssh:channel_id(), ExitSignal :: string(), ErrorMsg :: string(), LanguageString :: string()}.
A remote execution can terminate violently because of a signal. Then this message can be received. For details on valid string values, see RFC 4254 Section 6.10, which shows a special case of these signals.
-type exit_status_ch_msg() :: {exit_status, ssh:channel_id(), ExitStatus :: non_neg_integer()}.
When the command running at the other end terminates, the following message can
be sent to return the exit status of the command. A zero exit_status
usually
means that the command terminated successfully. This event is sent as a result
of calling ssh_connection:exit_status/3.
Types
-type channel_id() :: ssh:channel_id().
-type connection_ref() :: ssh:connection_ref().
-type reason() :: closed | timeout.
The result of a call.
If the request reached the peer, was handled and the response reached the
requesting node the req_status/0
is the status reported from the peer.
If not, the reason/0
indicates what went wrong:
closed
- indicates that the channel or connection was closed when trying to send the requesttimeout
- indicates that the operation exceeded a time limit
-type req_status() :: success | failure.
The status of a request. Corresponds to the SSH_MSG_CHANNEL_SUCCESS
and
SSH_MSG_CHANNEL_FAILURE
values in
RFC 4254, Section 5.4.
-type result() :: req_status() | {error, reason()}.
Equivalent to reason/0
.
-type ssh_data_type_code() :: non_neg_integer().
The valid values are 0
("normal") and 1
("stderr"), see
RFC 4254, Section 5.2.
Functions
-spec adjust_window(ConnectionRef, ChannelId, NumOfBytes) -> ok when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), NumOfBytes :: integer().
Adjusts the SSH flow control window. This is to be done by both the client- and server-side channel processes.
Note
Channels implemented with the
ssh_client_channel
behavior do not normally need to call this function as flow control is handled by the behavior. The behavior adjusts the window every time the callback handle_ssh_msg/2 returns after processing channel data.
-spec close(ConnectionRef, ChannelId) -> ok when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id().
A server- or client-channel process can choose to close their session by sending a close event.
Note
This function is called by the
ssh_client_channel
behavior when the channel is terminated, seessh_client_channel
. Thus, channels implemented with the behavior are not to call this function explicitly.
-spec exec(ConnectionRef, ChannelId, Command, Timeout) -> result() when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Command :: string(), Timeout :: timeout().
Is to be called by a client-channel process to request that the server starts
executing the given command. The result is several messages according to the
following pattern. The last message is a channel close message, as the exec
request is a one-time execution that closes the channel when it is done.
N x data message(s) - The result of executing the command can be only one line or thousands of lines depending on the command.
0 or 1 x eof message - Indicates that no more data is to be sent.
0 or 1 x exit signal message - Not all systems send signals. For details on valid string values, see RFC 4254, Section 6.10
0 or 1 x exit status message - It is recommended by the SSH Connection Protocol to send this message, but that is not always the case.
1 x closed status message - Indicates that the
ssh_client_channel
started for the execution of the command has now been shut down.
See the User's Guide section on One-Time Execution for examples.
-spec exit_status(ConnectionRef, ChannelId, Status) -> ok when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Status :: integer().
Is to be called by a server-channel process to send the exit status of a command to the client.
-spec ptty_alloc(ConnectionRef, ChannelId, Options) -> result() when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Options :: proplists:proplist().
Equivalent to ptty_alloc/4
.
ptty_alloc(ConnectionRef, ChannelId, Options, Timeout)
View Source (since OTP 17.4)-spec ptty_alloc(ConnectionRef, ChannelId, Options, Timeout) -> result() when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Options :: proplists:proplist(), Timeout :: timeout().
Sends an SSH Connection Protocol pty_req
, to allocate a pseudo-terminal. Is to
be called by an SSH client process.
Options:
{term, string()} - Defaults to os:getenv("TERM") or vt100 if it is undefined.
{width, integer()} - Defaults to 80 if
pixel_width
is not defined.{height, integer()} - Defaults to 24 if
pixel_height
is not defined.{pixel_width, integer()} - Is disregarded if
width
is defined.{pixel_height, integer()} - Is disregarded if
height
is defined.{pty_opts, [{posix_atom(), integer()}]} - Option can be an empty list. Otherwise, see possible POSIX names in Section 8 in RFC 4254.
-spec reply_request(ConnectionRef, WantReply, Status, ChannelId) -> ok when ConnectionRef :: ssh:connection_ref(), WantReply :: boolean(), Status :: req_status(), ChannelId :: ssh:channel_id().
Sends status replies to requests where the requester has stated that it wants a
status report, that is, WantReply = true
. If WantReply
is false
, calling
this function becomes a "noop". Is to be called while handling an SSH Connection
Protocol message containing a WantReply
boolean value.
-spec send(connection_ref(), channel_id(), iodata()) -> ok | {error, timeout | closed}.
Equivalent to send/5
.
-spec send(connection_ref(), channel_id(), iodata(), timeout()) -> ok | {error, reason()}; (connection_ref(), channel_id(), ssh_data_type_code(), iodata()) -> ok | {error, reason()}.
Equivalent to send(ConnectionRef, ChannelId, 0, Data, TimeOut) if called with TimeOut being integer.
Equivalent to send(ConnectionRef, ChannelId, 0, Data, infinity) if called with TimeOut being infinity atom.
Equivalent to send(ConnectionHandler, ChannelId, Type, Data, infinity) if called with last argument which is not integer or infinity atom.
-spec send(connection_ref(), channel_id(), ssh_data_type_code(), iodata(), timeout()) -> ok | {error, reason()}.
send(ConnectionRef, ChannelId, Type, Data, TimeOut) -> ok | Error
Is to be called by client- and server-channel processes to send data to each other.
The function subsystem/4
and subsequent calls of send/3,4,5
must be executed
in the same process.
-spec send_eof(ConnectionRef, ChannelId) -> ok | {error, closed} when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id().
Sends EOF on channel ChannelId
.
-spec session_channel(ConnectionRef, Timeout) -> Result when ConnectionRef :: ssh:connection_ref(), Timeout :: timeout(), Result :: {ok, ssh:channel_id()} | {error, reason()}.
Equivalent to session_channel/4
.
session_channel(ConnectionRef, InitialWindowSize, MaxPacketSize, Timeout)
View Source-spec session_channel(ConnectionRef, InitialWindowSize, MaxPacketSize, Timeout) -> Result when ConnectionRef :: ssh:connection_ref(), InitialWindowSize :: pos_integer() | undefined, MaxPacketSize :: pos_integer() | undefined, Timeout :: timeout(), Result :: {ok, ssh:channel_id()} | {error, reason()}.
Opens a channel for an SSH session. The channel id returned from this function is the id used as input to the other functions in this module.
-spec setenv(ConnectionRef, ChannelId, Var, Value, Timeout) -> success when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Var :: string(), Value :: string(), Timeout :: timeout().
Environment variables can be passed before starting the shell/command. Is to be called by a client channel processes.
-spec shell(ConnectionRef, ChannelId) -> Result when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Result :: ok | success | failure | {error, timeout}.
Is to be called by a client channel process to request that the user default shell (typically defined in /etc/passwd in Unix systems) is executed at the server end.
Note: the return value is ok
instead of success
unlike in other functions in
this module. This is a fault that was introduced so long ago that any change
would break a large number of existing software.
-spec subsystem(ConnectionRef, ChannelId, Subsystem, Timeout) -> result() when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Subsystem :: string(), Timeout :: timeout().
Is to be called by a client-channel process for requesting to execute a predefined subsystem on the server.
The function subsystem/4
and subsequent calls of
send/3,4,5 must be executed in the same process.