paramiko.Channel

Package paramiko :: Class Channel |
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## Type Channel

    object --+
             |
            Channel

A secure tunnel across an SSH `Transport`. A Channel is meant to behave like a socket, and has an API that should be indistinguishable from the python socket API.

Because SSH2 has a windowing kind of flow control, if you stop reading data from a Channel and its buffer fills up, the server will be unable to send you any more data until you read some of it. (This won't affect other channels on the same transport -- all channels on a single transport are flow-controlled independently.) Similarly, if the server isn't reading data you send, calls to `send` may block, unless you set a timeout. This is exactly like a normal network socket, so it shouldn't be too surprising.

Method Summary
| ``__init__`(self, chanid)` Create a new channel.
| `__del__(self)`
str | ``__repr__`(self)` Return a string representation of this object, for debugging.
| ``close`(self)` Close the channel.
bool | ``exec_command`(self, command)` Execute a command on the server.
int | ``fileno`(self)` Returns an OS-level file descriptor which can be used for polling, but but not for reading or writing).
int | ``get_id`(self)` Return the ID # for this channel.
str | ``get_name`(self)` Get the name of this channel that was previously set by `set_name`.
bool | ``get_pty`(self, term, width, height)` Request a pseudo-terminal from the server.
`Transport` | ``get_transport`(self)` Return the `Transport` associated with this channel.
float | ``gettimeout`(self)` Returns the timeout in seconds (as a float) associated with socket operations, or `None` if no timeout is set.
bool | ``invoke_shell`(self)` Request an interactive shell session on this channel.
bool | ``invoke_subsystem`(self, subsystem)` Request a subsystem on the server (for example, `sftp`).
`ChannelFile` | ``makefile`(self, *params)` Return a file-like object associated with this channel.
`ChannelFile` | ``makefile_stderr`(self, *params)` Return a file-like object associated with this channel's stderr stream.
str | ``recv`(self, nbytes)` Receive data from the channel.
int | ``recv_exit_status`(self)` Return the exit status from the process on the server.
boolean | ``recv_ready`(self)` Returns true if data is buffered and ready to be read from this channel.
str | ``recv_stderr`(self, nbytes)` Receive data from the channel's stderr stream.
boolean | ``recv_stderr_ready`(self)` Returns true if data is buffered and ready to be read from this channel's stderr stream.
bool | ``resize_pty`(self, width, height)` Resize the pseudo-terminal.
int | ``send`(self, s)` Send data to the channel.
| ``send_exit_status`(self, status)` Send the exit status of an executed command to the client.
int | ``send_stderr`(self, s)` Send data to the channel on the "stderr" stream.
| ``sendall`(self, s)` Send data to the channel, without allowing partial results.
| ``sendall_stderr`(self, s)` Send data to the channel's "stderr" stream, without allowing partial results.
bool | ``set_combine_stderr`(self, combine)` Set whether stderr should be combined into stdout on this channel.
| ``set_name`(self, name)` Set a name for this channel.
| ``setblocking`(self, blocking)` Set blocking or non-blocking mode of the channel: if `blocking` is 0, the channel is set to non-blocking mode; otherwise it's set to blocking mode.
| ``settimeout`(self, timeout)` Set a timeout on blocking read/write operations.
| ``shutdown`(self, how)` Shut down one or both halves of the connection.
| ``shutdown_read`(self)` Shutdown the receiving side of this socket, closing the stream in the incoming direction.
| ``shutdown_write`(self)` Shutdown the sending side of this socket, closing the stream in the outgoing direction.
Inherited from object
| ``__delattr__`(...)` x.__delattr__('name') <==> del x.name
| ``__getattribute__`(...)` x.__getattribute__('name') <==> x.name
| ``__hash__`(x)` x.__hash__() <==> hash(x)
| ``__new__`(T, S, ...)` T.__new__(S, ...) -> a new object with type S, a subtype of T
| ``__reduce__`(...)` helper for pickle
| ``__reduce_ex__`(...)` helper for pickle
| ``__setattr__`(...)` x.__setattr__('name', value) <==> x.name = value
| ``__str__`(x)` x.__str__() <==> str(x)

Class Variable Summary
`int` | `MIN_PACKET_SIZE` = 1024

Method Details

### __init__(self, chanid) (Constructor) Create a new channel. The channel is not associated with any particular session or `Transport` until the Transport attaches it. Normally you would only call this method from the constructor of a subclass of `Channel`. Parameters: `chanid` - the ID of this channel, as passed by an existing `Transport`. (type=int) Overrides: `__builtin__.object.__init__`

### __repr__(self) (Representation operator) Return a string representation of this object, for debugging. Returns: str Overrides: `__builtin__.object.__repr__`

### close(self) Close the channel. All future read/write operations on the channel will fail. The remote end will receive no more data (after queued data is flushed). Channels are automatically closed when their `Transport` is closed or when they are garbage collected.

### exec_command(self, command) Execute a command on the server. If the server allows it, the channel will then be directly connected to the stdin, stdout, and stderr of the command being executed. When the command finishes executing, the channel will be closed and can't be reused. You must open a new channel if you wish to execute another command. Parameters: `command` - a shell command to execute. (type=str) Returns: `True` if the operation succeeded; `False` if not. (type=bool)

### fileno(self) Returns an OS-level file descriptor which can be used for polling, but but not for reading or writing). This is primaily to allow python's `select` module to work. The first time `fileno` is called on a channel, a pipe is created to simulate real OS-level file descriptor (FD) behavior. Because of this, two OS-level FDs are created, which will use up FDs faster than normal. You won't notice this effect unless you open hundreds or thousands of channels simultaneously, but it's still notable. Returns: an OS-level file descriptor (type=int) Warning: This method causes channel reads to be slightly less efficient.

### get_id(self) Return the ID # for this channel. The channel ID is unique across a `Transport` and usually a small number. It's also the number passed to `ServerInterface.check_channel_request` when determining whether to accept a channel request in server mode. Returns: the ID of this channel. (type=int) Since: ivysaur

### get_name(self) Get the name of this channel that was previously set by `set_name`. Returns: the name of this channel. (type=str)

### get_pty(self, term='vt100', width=80, height=24) Request a pseudo-terminal from the server. This is usually used right after creating a client channel, to ask the server to provide some basic terminal semantics for a shell invoked with `invoke_shell`. It isn't necessary (or desirable) to call this method if you're going to exectue a single command with `exec_command`. Parameters: `term` - the terminal type to emulate (for example, `'vt100'`). (type=str) `width` - width (in characters) of the terminal screen (type=int) `height` - height (in characters) of the terminal screen (type=int) Returns: `True` if the operation succeeded; `False` if not. (type=bool)

### get_transport(self) Return the `Transport` associated with this channel. Returns: the `Transport` that was used to create this channel. (type=`Transport`)

### gettimeout(self) Returns the timeout in seconds (as a float) associated with socket operations, or `None` if no timeout is set. This reflects the last call to `setblocking` or `settimeout`. Returns: timeout in seconds, or `None`. (type=float)

### invoke_shell(self) Request an interactive shell session on this channel. If the server allows it, the channel will then be directly connected to the stdin, stdout, and stderr of the shell. Normally you would call `get_pty` before this, in which case the shell will operate through the pty, and the channel will be connected to the stdin and stdout of the pty. When the shell exits, the channel will be closed and can't be reused. You must open a new channel if you wish to open another shell. Returns: `True` if the operation succeeded; `False` if not. (type=bool)

### invoke_subsystem(self, subsystem) Request a subsystem on the server (for example, `sftp`). If the server allows it, the channel will then be directly connected to the requested subsystem. When the subsystem finishes, the channel will be closed and can't be reused. Parameters: `subsystem` - name of the subsystem being requested. (type=str) Returns: `True` if the operation succeeded; `False` if not. (type=bool)

### makefile(self, *params) Return a file-like object associated with this channel. The optional `mode` and `bufsize` arguments are interpreted the same way as by the built-in `file()` function in python. Returns: object which can be used for python file I/O. (type=`ChannelFile`)

### makefile_stderr(self, *params) Return a file-like object associated with this channel's stderr stream. Only channels using `exec_command` or `invoke_shell` without a pty will ever have data on the stderr stream. The optional `mode` and `bufsize` arguments are interpreted the same way as by the built-in `file()` function in python. For a client, it only makes sense to open this file for reading. For a server, it only makes sense to open this file for writing. Returns: object which can be used for python file I/O. (type=`ChannelFile`) Since: 1.1

### recv(self, nbytes) Receive data from the channel. The return value is a string representing the data received. The maximum amount of data to be received at once is specified by `nbytes`. If a string of length zero is returned, the channel stream has closed. Parameters: `nbytes` - maximum number of bytes to read. (type=int) Returns: data. (type=str) Raises: `socket.timeout` - if no data is ready before the timeout set by `settimeout`.

### recv_exit_status(self) Return the exit status from the process on the server. This is mostly useful for retrieving the reults of an `exec_command`. If the command hasn't finished yet, this method will wait until it does, or until the channel is closed. If no exit status is provided by the server, -1 is returned. Returns: the exit code of the process on the server. (type=int) Since: 1.2

### recv_ready(self) Returns true if data is buffered and ready to be read from this channel. A `False` result does not mean that the channel has closed; it means you may need to wait before more data arrives. Returns: `True` if a `recv` call on this channel would immediately return at least one byte; `False` otherwise. (type=boolean)

### recv_stderr(self, nbytes) Receive data from the channel's stderr stream. Only channels using `exec_command` or `invoke_shell` without a pty will ever have data on the stderr stream. The return value is a string representing the data received. The maximum amount of data to be received at once is specified by `nbytes`. If a string of length zero is returned, the channel stream has closed. Parameters: `nbytes` - maximum number of bytes to read. (type=int) Returns: data. (type=str) Raises: `socket.timeout` - if no data is ready before the timeout set by `settimeout`. Since: 1.1

### recv_stderr_ready(self) Returns true if data is buffered and ready to be read from this channel's stderr stream. Only channels using `exec_command` or `invoke_shell` without a pty will ever have data on the stderr stream. Returns: `True` if a `recv_stderr` call on this channel would immediately return at least one byte; `False` otherwise. (type=boolean) Since: 1.1

### resize_pty(self, width=80, height=24) Resize the pseudo-terminal. This can be used to change the width and height of the terminal emulation created in a previous `get_pty` call. Parameters: `width` - new width (in characters) of the terminal screen (type=int) `height` - new height (in characters) of the terminal screen (type=int) Returns: `True` if the operation succeeded; `False` if not. (type=bool)

### send(self, s) Send data to the channel. Returns the number of bytes sent, or 0 if the channel stream is closed. Applications are responsible for checking that all data has been sent: if only some of the data was transmitted, the application needs to attempt delivery of the remaining data. Parameters: `s` - data to send. (type=str) Returns: number of bytes actually sent. (type=int) Raises: `socket.timeout` - if no data could be sent before the timeout set by `settimeout`.

### send_exit_status(self, status) Send the exit status of an executed command to the client. (This really only makes sense in server mode.) Many clients expect to get some sort of status code back from an executed command after it completes. Parameters: `status` - the exit code of the process (type=int) Since: 1.2

### send_stderr(self, s) Send data to the channel on the "stderr" stream. This is normally only used by servers to send output from shell commands -- clients won't use this. Returns the number of bytes sent, or 0 if the channel stream is closed. Applications are responsible for checking that all data has been sent: if only some of the data was transmitted, the application needs to attempt delivery of the remaining data. Parameters: `s` - data to send. (type=str) Returns: number of bytes actually sent. (type=int) Raises: `socket.timeout` - if no data could be sent before the timeout set by `settimeout`. Since: 1.1

### sendall(self, s) Send data to the channel, without allowing partial results. Unlike `send`, this method continues to send data from the given string until either all data has been sent or an error occurs. Nothing is returned. Parameters: `s` - data to send. (type=str) Raises: `socket.timeout` - if sending stalled for longer than the timeout set by `settimeout`. `socket.error` - if an error occured before the entire string was sent. Note: If the channel is closed while only part of the data hase been sent, there is no way to determine how much data (if any) was sent. This is irritating, but identically follows python's API.

### sendall_stderr(self, s) Send data to the channel's "stderr" stream, without allowing partial results. Unlike `send_stderr`, this method continues to send data from the given string until all data has been sent or an error occurs. Nothing is returned. Parameters: `s` - data to send to the client as "stderr" output. (type=str) Raises: `socket.timeout` - if sending stalled for longer than the timeout set by `settimeout`. `socket.error` - if an error occured before the entire string was sent. Since: 1.1

### set_combine_stderr(self, combine) Set whether stderr should be combined into stdout on this channel. The default is `False`, but in some cases it may be convenient to have both streams combined. If this is `False`, and `exec_command` is called (or `invoke_shell` with no pty), output to stderr will not show up through the `recv` and `recv_ready` calls. You will have to use `recv_stderr` and `recv_stderr_ready` to get stderr output. If this is `True`, data will never show up via `recv_stderr` or `recv_stderr_ready`. Parameters: `combine` - `True` if stderr output should be combined into stdout on this channel. (type=bool) Returns: previous setting. (type=bool) Since: 1.1

### set_name(self, name) Set a name for this channel. Currently it's only used to set the name of the log level used for debugging. The name can be fetched with the `get_name` method. Parameters: `name` - new channel name. (type=str)

### setblocking(self, blocking) Set blocking or non-blocking mode of the channel: if `blocking` is 0, the channel is set to non-blocking mode; otherwise it's set to blocking mode. Initially all channels are in blocking mode. In non-blocking mode, if a `recv` call doesn't find any data, or if a `send` call can't immediately dispose of the data, an error exception is raised. In blocking mode, the calls block until they can proceed. `chan.setblocking(0)` is equivalent to `chan.settimeout(0)`; `chan.setblocking(1)` is equivalent to `chan.settimeout(None)`. Parameters: `blocking` - 0 to set non-blocking mode; non-0 to set blocking mode. (type=int)

### settimeout(self, timeout) Set a timeout on blocking read/write operations. The `timeout` argument can be a nonnegative float expressing seconds, or `None`. If a float is given, subsequent channel read/write operations will raise a timeout exception if the timeout period value has elapsed before the operation has completed. Setting a timeout of `None` disables timeouts on socket operations. `chan.settimeout(0.0)` is equivalent to `chan.setblocking(0)`; `chan.settimeout(None)` is equivalent to `chan.setblocking(1)`. Parameters: `timeout` - seconds to wait for a pending read/write operation before raising `socket.timeout`, or `None` for no timeout. (type=float)

### shutdown(self, how) Shut down one or both halves of the connection. If `how` is 0, further receives are disallowed. If `how` is 1, further sends are disallowed. If `how` is 2, further sends and receives are disallowed. This closes the stream in one or both directions. Parameters: `how` - 0 (stop receiving), 1 (stop sending), or 2 (stop receiving and sending). (type=int)

### shutdown_read(self) Shutdown the receiving side of this socket, closing the stream in the incoming direction. After this call, future reads on this channel will fail instantly. This is a convenience method, equivalent to `shutdown(0)`, for people who don't make it a habit to memorize unix constants from the 1970s. Since: 1.2

### shutdown_write(self) Shutdown the sending side of this socket, closing the stream in the outgoing direction. After this call, future writes on this channel will fail instantly. This is a convenience method, equivalent to `shutdown(1)`, for people who don't make it a habit to memorize unix constants from the 1970s. Since: 1.2

Class Variable Details

    ### MIN_PACKET_SIZE Type: `int` Value:
        1024

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