ssh_connection (ssh v4.12.3)
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, ssh:connection_ref(), channel_msg()}
If the ssh_client_channel behavior is used to implement the channel process, these messages are handled by handle_ssh_msg/2.
Link to this section Summary
Types
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.
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.
Data has arrived on the channel. This event is sent as a result of calling ssh_connection:send/[3,4,5].
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.
Indicates that the other side sends no more data. This event is sent as a result of calling ssh_connection:send_eof/2.
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.
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 .
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.
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.
The result of a call.
The status of a request. Coresponds to the SSH_MSG_CHANNEL_SUCCESS and SSH_MSG_CHANNEL_FAILURE values in RFC 4254, Section 5.4.
The result of a call.
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.
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.
The valid values are 0 ("normal") and 1 ("stderr"), see RFC 4254, Section 5.2.
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.
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.
When the window (terminal) size changes on the client side, it can send a message to the server side to inform it of the new dimensions. No API function generates this event.
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.
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.
- ConnectionRef = ssh:connection_ref()
- ChannelId = ssh:channel_id()
- Data = iodata()
- Type = ssh_data_type_code()
- Timeout = timeout()
- Error = {error, reason()}
Is to be called by client- and server-channel processes to send data to each other.
Sends EOF on channel ChannelId.
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.
Link to this section Types
-type channel_msg() :: term().
Specs
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 closed_ch_msg() :: term().
Specs
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 data_ch_msg() :: term().
Specs
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].
-type env_ch_msg() :: term().
Specs
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.
-type eof_ch_msg() :: term().
Specs
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.
-type event() :: term().
Specs
event() :: {ssh_cm, ssh:connection_ref(), channel_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 exec_ch_msg() :: term().
Specs
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 exit_signal_ch_msg() :: term().
Specs
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() :: term().
Specs
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.
-type pty_ch_msg() :: term().
Specs
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()]}}.
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.
-type reason() :: term().
Specs
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() is the status reported from the peer.
If not, the reason() indicates what went wrong:
closed- indicates that the channel or connection was closed when trying to send the request
timeout- indicates that the operation exceeded a time limit
-type req_status() :: term().
Specs
req_status() :: success | failure.
The status of a request. Coresponds to the SSH_MSG_CHANNEL_SUCCESS and SSH_MSG_CHANNEL_FAILURE values in RFC 4254, Section 5.4.
-type result() :: term().
Specs
result() :: req_status() | {error, reason()}.
The result of a call.
If the request reached the peer, was handled and the response reached the requesting node the req_status() is the status reported from the peer.
If not, the reason() indicates what went wrong:
closed- indicates that the channel or connection was closed when trying to send the request
timeout- indicates that the operation exceeded a time limit
-type shell_ch_msg() :: term().
Specs
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.
-type signal_ch_msg() :: term().
Specs
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.
-type ssh_data_type_code() :: term().
Specs
ssh_data_type_code() :: non_neg_integer().
The valid values are 0 ("normal") and 1 ("stderr"), see RFC 4254, Section 5.2.
-type term_mode() :: term().
Specs
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.
-type want_reply() :: term().
Specs
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.
-type window_change_ch_msg() :: term().
Specs
window_change_ch_msg() ::
{window_change,
ssh:channel_id(),
CharWidth :: non_neg_integer(),
RowHeight :: non_neg_integer(),
PixelWidth :: non_neg_integer(),
PixelHeight :: non_neg_integer()}.
When the window (terminal) size changes on the client side, it can send a message to the server side to inform it of the new dimensions. No API function generates this event.
Link to this section Functions
adjust_window/3
Specs
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.
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.
close/2
Specs
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.
This function is called by the ssh_client_channel behavior when the channel is terminated, see ssh_client_channel(3). Thus, channels implemented with the behavior are not to call this function explicitly.
exec/4
Specs
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_channelstarted for the execution of the command has now been shut down.
See the User's Guide section on One-Time Execution for examples.
exit_status/3
Specs
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.
Specs
ptty_alloc(ConnectionRef, ChannelId, Options) -> result() when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Options :: proplists:proplist().
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_widthis not defined.- {height, integer()}
Defaults to 24 if
pixel_heightis not defined.- {pixel_width, integer()}
Is disregarded if
widthis defined.- {pixel_height, integer()}
Is disregarded if
heightis defined.- {pty_opts, [{posix_atom(), integer()}]}
Option can be an empty list. Otherwise, see possible POSIX names in Section 8 in RFC 4254.
Specs
ptty_alloc(ConnectionRef, ChannelId, Options, Timeout) -> result() when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id(), Options :: proplists:proplist(), Timeout :: timeout().
reply_request/4
Specs
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.
send(ConnectionRef, ChannelId, Data) ->
Specs
send(connection_ref(), channel_id(), iodata()) -> ok | {error, timeout | closed}.
- ConnectionRef = ssh:connection_ref()
- ChannelId = ssh:channel_id()
- Data = iodata()
- Type = ssh_data_type_code()
- Timeout = timeout()
- Error = {error, reason()}
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.
send(ConnectionRef, ChannelId, Type, Data) -> send(ConnectionRef, ChannelId, Data, Timeout) ->
Specs
send(connection_ref(), channel_id(), iodata(), timeout()) -> ok | {error, reason()}; (connection_ref(), channel_id(), ssh_data_type_code(), iodata()) -> ok | {error, reason()}.
send(ConnectionRef, ChannelId, Type, Data, TimeOut) -> ok | Error
Specs
send(connection_ref(), channel_id(), ssh_data_type_code(), iodata(), timeout()) -> ok | {error, reason()}.
send_eof/2
Specs
send_eof(ConnectionRef, ChannelId) -> ok | {error, closed}
when ConnectionRef :: ssh:connection_ref(), ChannelId :: ssh:channel_id().
Sends EOF on channel ChannelId.
session_channel/2
Specs
session_channel(ConnectionRef, Timeout) -> Result
when
ConnectionRef :: ssh:connection_ref(),
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.
session_channel/4
Specs
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()}.
setenv/5
Specs
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.
shell/2
Specs
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.
subsystem/4
Specs
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.