The SSH channel functions

Collaboration diagram for The SSH channel functions:

Functions
ssh_channel	ssh_channel_new (ssh_session session)
	Allocate a new channel.
uint32_t	ssh_channel_new_id (ssh_session session)
	SSH_PACKET_CALLBACK (ssh_packet_channel_open_conf)
	SSH_PACKET_CALLBACK (ssh_packet_channel_open_fail)
ssh_channel	ssh_channel_from_local (ssh_session session, uint32_t id)
	SSH_PACKET_CALLBACK (channel_rcv_change_window)
	SSH_PACKET_CALLBACK (channel_rcv_data)
	SSH_PACKET_CALLBACK (channel_rcv_eof)
	SSH_PACKET_CALLBACK (channel_rcv_close)
	SSH_PACKET_CALLBACK (channel_rcv_request)
int	channel_default_bufferize (ssh_channel channel, void *data, uint32_t len, bool is_stderr)
int	ssh_channel_open_session (ssh_channel channel)
	Open a session channel (suited for a shell, not TCP forwarding).
int	ssh_channel_open_auth_agent (ssh_channel channel)
	Open an agent authentication forwarding channel. This type of channel can be opened by a server towards a client in order to provide SSH-Agent services to the server-side process. This channel can only be opened if the client claimed support by sending a channel request beforehand.
int	ssh_channel_open_forward (ssh_channel channel, const char *remotehost, int remoteport, const char *sourcehost, int localport)
	Open a TCP/IP forwarding channel.
int	ssh_channel_open_forward_unix (ssh_channel channel, const char *remotepath, const char *sourcehost, int localport)
	Open a TCP/IP - UNIX domain socket forwarding channel.
void	ssh_channel_free (ssh_channel channel)
	Close and free a channel.
void	ssh_channel_do_free (ssh_channel channel)
int	ssh_channel_send_eof (ssh_channel channel)
	Send an end of file on the channel.
int	ssh_channel_close (ssh_channel channel)
	Close a channel.
int	ssh_channel_flush (ssh_channel channel)
uint32_t	ssh_channel_window_size (ssh_channel channel)
	Get the remote window size.
int	ssh_channel_write (ssh_channel channel, const void *data, uint32_t len)
	Blocking write on a channel.
int	ssh_channel_is_open (ssh_channel channel)
	Check if the channel is open or not.
int	ssh_channel_is_closed (ssh_channel channel)
	Check if the channel is closed or not.
int	ssh_channel_is_eof (ssh_channel channel)
	Check if remote has sent an EOF.
void	ssh_channel_set_blocking (ssh_channel channel, int blocking)
	Put the channel into blocking or nonblocking mode.
	SSH_PACKET_CALLBACK (ssh_packet_channel_success)
	SSH_PACKET_CALLBACK (ssh_packet_channel_failure)
int	ssh_channel_request_pty_size (ssh_channel channel, const char *terminal, int col, int row)
	Request a pty with a specific type and size.
int	ssh_channel_request_pty (ssh_channel channel)
	Request a PTY.
int	ssh_channel_change_pty_size (ssh_channel channel, int cols, int rows)
	Change the size of the terminal associated to a channel.
int	ssh_channel_request_shell (ssh_channel channel)
	Request a shell.
int	ssh_channel_request_subsystem (ssh_channel channel, const char *subsys)
	Request a subsystem (for example "sftp").
int	ssh_channel_request_sftp (ssh_channel channel)
	Request sftp subsystem on the channel.
int	ssh_channel_request_x11 (ssh_channel channel, int single_connection, const char *protocol, const char *cookie, int screen_number)
	Sends the "x11-req" channel request over an existing session channel.
ssh_channel	ssh_channel_accept_x11 (ssh_channel channel, int timeout_ms)
	Accept an X11 forwarding channel.
int	ssh_channel_request_auth_agent (ssh_channel channel)
	Send an "auth-agent-req" channel request over an existing session channel.
	SSH_PACKET_CALLBACK (ssh_request_success)
	SSH_PACKET_CALLBACK (ssh_request_denied)
int	ssh_channel_listen_forward (ssh_session session, const char *address, int port, int *bound_port)
	Sends the "tcpip-forward" global request to ask the server to begin listening for inbound connections.
int	ssh_forward_listen (ssh_session session, const char *address, int port, int *bound_port)
ssh_channel	ssh_forward_accept (ssh_session session, int timeout_ms)
ssh_channel	ssh_channel_accept_forward (ssh_session session, int timeout_ms, int *destination_port)
	Accept an incoming TCP/IP forwarding channel and get some information about incoming connection.
ssh_channel	ssh_channel_open_forward_port (ssh_session session, int timeout_ms, int *destination_port, char **originator, int *originator_port)
	Accept an incoming TCP/IP forwarding channel and get information about incoming connection.
int	ssh_channel_cancel_forward (ssh_session session, const char *address, int port)
	Sends the "cancel-tcpip-forward" global request to ask the server to cancel the tcpip-forward request.
int	ssh_forward_cancel (ssh_session session, const char *address, int port)
int	ssh_channel_request_env (ssh_channel channel, const char *name, const char *value)
	Set environment variables.
int	ssh_channel_request_exec (ssh_channel channel, const char *cmd)
	Run a shell command without an interactive shell.
int	ssh_channel_request_send_signal (ssh_channel channel, const char *sig)
	Send a signal to remote process (as described in RFC 4254, section 6.9).
int	ssh_channel_request_send_break (ssh_channel channel, uint32_t length)
	Send a break signal to the server (as described in RFC 4335).
int	channel_read_buffer (ssh_channel channel, ssh_buffer buffer, uint32_t count, int is_stderr)
	Read data from a channel into a buffer.
int	ssh_channel_read (ssh_channel channel, void *dest, uint32_t count, int is_stderr)
	Reads data from a channel.
int	ssh_channel_read_timeout (ssh_channel channel, void *dest, uint32_t count, int is_stderr, int timeout_ms)
	Reads data from a channel.
int	ssh_channel_read_nonblocking (ssh_channel channel, void *dest, uint32_t count, int is_stderr)
	Do a nonblocking read on the channel.
int	ssh_channel_poll (ssh_channel channel, int is_stderr)
	Polls a channel for data to read.
int	ssh_channel_poll_timeout (ssh_channel channel, int timeout, int is_stderr)
	Polls a channel for data to read, waiting for a certain timeout.
ssh_session	ssh_channel_get_session (ssh_channel channel)
	Recover the session in which belongs a channel.
int	ssh_channel_get_exit_status (ssh_channel channel)
	Get the exit status of the channel (error code from the executed instruction).
int	ssh_channel_select (ssh_channel *readchans, ssh_channel *writechans, ssh_channel *exceptchans, struct timeval *timeout)
	Act like the standard select(2) on channels.
void	ssh_channel_set_counter (ssh_channel channel, ssh_counter counter)
	Set the channel data counter.
int	ssh_channel_write_stderr (ssh_channel channel, const void *data, uint32_t len)
	Blocking write on a channel stderr.
int	ssh_channel_open_reverse_forward (ssh_channel channel, const char *remotehost, int remoteport, const char *sourcehost, int localport)
	Open a TCP/IP reverse forwarding channel.
int	ssh_channel_open_x11 (ssh_channel channel, const char *orig_addr, int orig_port)
	Open a X11 channel.
int	ssh_channel_request_send_exit_status (ssh_channel channel, int exit_status)
	Send the exit status to the remote process.
int	ssh_channel_request_send_exit_signal (ssh_channel channel, const char *sig, int core, const char *errmsg, const char *lang)
	Send an exit signal to remote process (RFC 4254, section 6.10).

Detailed Description

Functions that manage a SSH channel.

Function Documentation

channel_read_buffer()

int channel_read_buffer	(	ssh_channel	channel,
		ssh_buffer	buffer,
		uint32_t	count,
		int	is_stderr )

Read data from a channel into a buffer.

Parameters

[in]	channel	The channel to read from.
[out]	buffer	The buffer which will get the data.
[in]	count	The count of bytes to be read. If it is bigger than 0, the exact size will be read, else (bytes=0) it will return once anything is available.
	is_stderr	A boolean value to mark reading from the stderr stream.

Returns

The number of bytes read, 0 on end of file or SSH_ERROR on error.

Deprecated

Please use ssh_channel_read instead

Warning

This function doesn't work in nonblocking/timeout mode

See also

ssh_channel_read

ssh_channel_accept_forward()

ssh_channel ssh_channel_accept_forward	(	ssh_session	session,
		int	timeout_ms,
		int *	destination_port )

Accept an incoming TCP/IP forwarding channel and get some information about incoming connection.

Parameters

[in]	session	The ssh session to use.
[in]	timeout_ms	A timeout in milliseconds.
[in]	destination_port	A pointer to destination port or NULL.

Returns

Newly created channel, or NULL if no incoming channel request from the server

ssh_channel_accept_x11()

ssh_channel ssh_channel_accept_x11	(	ssh_channel	channel,
		int	timeout_ms )

Accept an X11 forwarding channel.

Parameters

[in]	channel	An x11-enabled session channel.
[in]	timeout_ms	Timeout in milliseconds.

Returns

A newly created channel, or NULL if no X11 request from the server.

ssh_channel_cancel_forward()

int ssh_channel_cancel_forward	(	ssh_session	session,
		const char *	address,
		int	port )

Sends the "cancel-tcpip-forward" global request to ask the server to cancel the tcpip-forward request.

Parameters

[in]	session	The ssh session to send the request.
[in]	address	The bound address on the server.
[in]	port	The bound port on the server.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

ssh_channel_change_pty_size()

int ssh_channel_change_pty_size	(	ssh_channel	channel,
		int	cols,
		int	rows )

Change the size of the terminal associated to a channel.

Parameters

[in]	channel	The channel to change the size.
[in]	cols	The new number of columns.
[in]	rows	The new number of rows.

Returns

SSH_OK on success, SSH_ERROR if an error occurred.

Warning

Do not call it from a signal handler if you are not sure any other libssh function using the same channel/session is running at the same time (not 100% threadsafe).

ssh_channel_close()

int ssh_channel_close

(

ssh_channel

channel

)

Close a channel.

This sends an end of file and then closes the channel. You won't be able to recover any data the server was going to send or was in buffers.

Parameters

[in]

channel

The channel to close.

Returns

SSH_OK on success, SSH_ERROR if an error occurred.

See also

ssh_channel_free()

ssh_channel_is_eof()

ssh_channel_free()

void ssh_channel_free

(

ssh_channel

channel

)

Close and free a channel.

Parameters

[in]

channel

The channel to free.

Warning

Any data unread on this channel will be lost.

ssh_channel_get_exit_status()

int ssh_channel_get_exit_status

(

ssh_channel

channel

)

Get the exit status of the channel (error code from the executed instruction).

Parameters

[in]

channel

The channel to get the status from.

Returns

The exit status, -1 if no exit status has been returned (yet), or SSH_ERROR on error.

Warning

This function may block until a timeout (or never) if the other side is not willing to close the channel. When a channel is freed the function returns SSH_ERROR immediately.

If you're looking for an async handling of this register a callback for the exit status.

See also

ssh_channel_exit_status_callback

ssh_channel_get_session()

ssh_session ssh_channel_get_session

(

ssh_channel

channel

)

Recover the session in which belongs a channel.

Parameters

[in]

channel

The channel to recover the session from.

Returns

The session pointer.

ssh_channel_is_closed()

int ssh_channel_is_closed

(

ssh_channel

channel

)

Check if the channel is closed or not.

Parameters

[in]

channel

The channel to check.

Returns

0 if channel is opened, nonzero otherwise.

See also

ssh_channel_is_open()

ssh_channel_is_eof()

int ssh_channel_is_eof

(

ssh_channel

channel

)

Check if remote has sent an EOF.

Parameters

[in]

channel

The channel to check.

Returns

0 if there is no EOF, nonzero otherwise.

ssh_channel_is_open()

int ssh_channel_is_open

(

ssh_channel

channel

)

Check if the channel is open or not.

Parameters

[in]

channel

The channel to check.

Returns

0 if channel is closed, nonzero otherwise.

See also

ssh_channel_is_closed()

ssh_channel_listen_forward()

int ssh_channel_listen_forward	(	ssh_session	session,
		const char *	address,
		int	port,
		int *	bound_port )

Sends the "tcpip-forward" global request to ask the server to begin listening for inbound connections.

Parameters

[in]	session	The ssh session to send the request.
[in]	address	The address to bind to on the server. Pass NULL to bind to all available addresses on all protocol families supported by the server.
[in]	port	The port to bind to on the server. Pass 0 to ask the server to allocate the next available unprivileged port number
[in]	bound_port	The pointer to get actual bound port. Pass NULL to ignore.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

ssh_channel_new()

ssh_channel ssh_channel_new

(

ssh_session

session

)

Allocate a new channel.

Parameters

[in]

session

The ssh session to use.

Returns

A pointer to a newly allocated channel, NULL on error. The channel needs to be freed with ssh_channel_free().

See also

ssh_channel_free()

ssh_channel_open_auth_agent()

int ssh_channel_open_auth_agent

(

ssh_channel

channel

)

Open an agent authentication forwarding channel. This type of channel can be opened by a server towards a client in order to provide SSH-Agent services to the server-side process. This channel can only be opened if the client claimed support by sending a channel request beforehand.

Parameters

[in]

channel

An allocated channel.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

See also

ssh_channel_open_forward()

ssh_channel_open_forward()

int ssh_channel_open_forward	(	ssh_channel	channel,
		const char *	remotehost,
		int	remoteport,
		const char *	sourcehost,
		int	localport )

Open a TCP/IP forwarding channel.

Parameters

[in]	channel	An allocated channel.
[in]	remotehost	The remote host to connected (host name or IP).
[in]	remoteport	The remote port.
[in]	sourcehost	The numeric IP address of the machine from where the connection request originates. This is mostly for logging purposes.
[in]	localport	The port on the host from where the connection originated. This is mostly for logging purposes.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Warning

This function does not bind the local port and does not automatically forward the content of a socket to the channel. You still have to use ssh_channel_read and ssh_channel_write for this.

ssh_channel_open_forward_port()

ssh_channel ssh_channel_open_forward_port	(	ssh_session	session,
		int	timeout_ms,
		int *	destination_port,
		char **	originator,
		int *	originator_port )

Accept an incoming TCP/IP forwarding channel and get information about incoming connection.

Parameters

[in]	session	The ssh session to use.
[in]	timeout_ms	A timeout in milliseconds.
[out]	destination_port	A pointer to destination port or NULL.
[out]	originator	A pointer to a pointer to a string of originator host or NULL. That the caller is responsible for to ssh_string_free_char().
[out]	originator_port	A pointer to originator port or NULL.

Returns

Newly created channel, or NULL if no incoming channel request from the server

See also

ssh_string_free_char()

ssh_channel_open_forward_unix()

int ssh_channel_open_forward_unix	(	ssh_channel	channel,
		const char *	remotepath,
		const char *	sourcehost,
		int	localport )

Open a TCP/IP - UNIX domain socket forwarding channel.

Parameters

[in]	channel	An allocated channel.
[in]	remotepath	The UNIX socket path on the remote machine
[in]	sourcehost	The numeric IP address of the machine from where the connection request originates. This is mostly for logging purposes.
[in]	localport	The port on the host from where the connection originated. This is mostly for logging purposes.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Warning

This function does not bind the local port and does not automatically forward the content of a socket to the channel. You still have to use ssh_channel_read and ssh_channel_write for this.

Requires support of OpenSSH for UNIX domain socket forwarding.

ssh_channel_open_reverse_forward()

int ssh_channel_open_reverse_forward	(	ssh_channel	channel,
		const char *	remotehost,
		int	remoteport,
		const char *	sourcehost,
		int	localport )

Open a TCP/IP reverse forwarding channel.

Parameters

[in]	channel	An allocated channel.
[in]	remotehost	The remote host to connected (host name or IP).
[in]	remoteport	The remote port.
[in]	sourcehost	The source host (your local computer). It's optional and for logging purpose.
[in]	localport	The source port (your local computer). It's optional and for logging purpose.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Warning

This function does not bind the local port and does not automatically forward the content of a socket to the channel. You still have to use ssh_channel_read and ssh_channel_write for this.

ssh_channel_open_session()

int ssh_channel_open_session

(

ssh_channel

channel

)

Open a session channel (suited for a shell, not TCP forwarding).

Parameters

[in]

channel

An allocated channel.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

See also

ssh_channel_open_forward()

ssh_channel_request_env()

ssh_channel_request_shell()

ssh_channel_request_exec()

ssh_channel_open_x11()

int ssh_channel_open_x11	(	ssh_channel	channel,
		const char *	orig_addr,
		int	orig_port )

Open a X11 channel.

Parameters

[in]	channel	An allocated channel.
[in]	orig_addr	The source host (the local server).
[in]	orig_port	The source port (the local server).

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Warning

This function does not bind the local port and does not automatically forward the content of a socket to the channel. You still have to use shh_channel_read and ssh_channel_write for this.

ssh_channel_poll()

int ssh_channel_poll	(	ssh_channel	channel,
		int	is_stderr )

Polls a channel for data to read.

Parameters

[in]	channel	The channel to poll.
[in]	is_stderr	A boolean to select the stderr stream.

Returns

The number of bytes available for reading, 0 if nothing is available or SSH_ERROR on error. When a channel is freed the function returns SSH_ERROR immediately.

Warning

When the channel is in EOF state, the function returns SSH_EOF.

See also

ssh_channel_is_eof()

ssh_channel_poll_timeout()

int ssh_channel_poll_timeout	(	ssh_channel	channel,
		int	timeout,
		int	is_stderr )

Polls a channel for data to read, waiting for a certain timeout.

Parameters

[in]	channel	The channel to poll.
[in]	timeout	Set an upper limit on the time for which this function will block, in milliseconds. Specifying a negative value means an infinite timeout. This parameter is passed to the poll() function.
[in]	is_stderr	A boolean to select the stderr stream.

Returns

The number of bytes available for reading, 0 if nothing is available (timeout elapsed), SSH_EOF on end of file, SSH_ERROR on error.

Warning

When the channel is in EOF state, the function returns SSH_EOF. When a channel is freed the function returns SSH_ERROR immediately.

See also

ssh_channel_is_eof()

ssh_channel_read()

int ssh_channel_read	(	ssh_channel	channel,
		void *	dest,
		uint32_t	count,
		int	is_stderr )

Reads data from a channel.

Parameters

[in]	channel	The channel to read from.
[out]	dest	The destination buffer which will get the data.
[in]	count	The count of bytes to be read.
[in]	is_stderr	A boolean value to mark reading from the stderr flow.

Returns

The number of bytes read, 0 on end of file or SSH_ERROR on error. In nonblocking mode it can return 0 if no data is available or SSH_AGAIN.

Warning

This function may return less than count bytes of data, and won't block until count bytes have been read.

ssh_channel_read_nonblocking()

int ssh_channel_read_nonblocking	(	ssh_channel	channel,
		void *	dest,
		uint32_t	count,
		int	is_stderr )

Do a nonblocking read on the channel.

A nonblocking read on the specified channel. it will return <= count bytes of data read atomically. It will also trigger any callbacks set on the channel.

Parameters

[in]	channel	The channel to read from.
[out]	dest	A pointer to a destination buffer.
[in]	count	The count of bytes of data to be read.
[in]	is_stderr	A boolean to select the stderr stream.

Returns

The number of bytes read (0 if nothing is available), SSH_ERROR on error, and SSH_EOF if the channel is EOF.

See also

ssh_channel_is_eof()

ssh_channel_read_timeout()

int ssh_channel_read_timeout	(	ssh_channel	channel,
		void *	dest,
		uint32_t	count,
		int	is_stderr,
		int	timeout_ms )

Reads data from a channel.

Parameters

[in]	channel	The channel to read from.
[out]	dest	The destination buffer which will get the data.
[in]	count	The count of bytes to be read.
[in]	is_stderr	A boolean value to mark reading from the stderr flow.
[in]	timeout_ms	A timeout in milliseconds. A value of -1 means infinite timeout.

Returns

The number of bytes read, 0 on end of file or SSH_ERROR on error. In nonblocking mode it Can return 0 if no data is available or SSH_AGAIN.

Warning

This function may return less than count bytes of data, and won't block until count bytes have been read.

ssh_channel_request_auth_agent()

int ssh_channel_request_auth_agent

(

ssh_channel

channel

)

Send an "auth-agent-req" channel request over an existing session channel.

This client-side request will enable forwarding the agent over an secure tunnel. When the server is ready to open one authentication agent channel, an ssh_channel_open_request_auth_agent_callback event will be generated.

Parameters

[in]

channel

The channel to send signal.

Returns

SSH_OK on success, SSH_ERROR if an error occurred

ssh_channel_request_env()

int ssh_channel_request_env	(	ssh_channel	channel,
		const char *	name,
		const char *	value )

Set environment variables.

Parameters

[in]	channel	The channel to set the environment variables.
[in]	name	The name of the variable.
[in]	value	The value to set.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Warning

Some environment variables may be refused by security reasons.

ssh_channel_request_exec()

int ssh_channel_request_exec	(	ssh_channel	channel,
		const char *	cmd )

Run a shell command without an interactive shell.

This is similar to 'sh -c command'.

Parameters

[in]	channel	The channel to execute the command.
[in]	cmd	The command to execute (e.g. "ls ~/ -al | grep -i reports").

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Example:

rc = ssh_channel_request_exec(channel, "ps aux");
if (rc > 0) {
    return -1;
}
 
while ((rc = ssh_channel_read(channel, buffer, sizeof(buffer), 0)) > 0) {
    if (fwrite(buffer, 1, rc, stdout) != (unsigned int) rc) {
        return -1;
    }
}

See also

ssh_channel_request_shell()

ssh_channel_request_pty()

int ssh_channel_request_pty

(

ssh_channel

channel

)

Request a PTY.

Parameters

[in]

channel

The channel to send the request.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

See also

ssh_channel_request_pty_size()

ssh_channel_request_pty_size()

int ssh_channel_request_pty_size	(	ssh_channel	channel,
		const char *	terminal,
		int	col,
		int	row )

Request a pty with a specific type and size.

Parameters

[in]	channel	The channel to send the request.
[in]	terminal	The terminal type ("vt100, xterm,...").
[in]	col	The number of columns.
[in]	row	The number of rows.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

ssh_channel_request_send_break()

int ssh_channel_request_send_break	(	ssh_channel	channel,
		uint32_t	length )

Send a break signal to the server (as described in RFC 4335).

Sends a break signal to the remote process. Note, that remote system may not support breaks. In such a case this request will be silently ignored.

Parameters

[in]	channel	The channel to send the break to.
[in]	length	The break-length in milliseconds to send.

Returns

SSH_OK on success, SSH_ERROR if an error occurred

ssh_channel_request_send_exit_signal()

int ssh_channel_request_send_exit_signal	(	ssh_channel	channel,
		const char *	sig,
		int	core,
		const char *	errmsg,
		const char *	lang )

Send an exit signal to remote process (RFC 4254, section 6.10).

This sends the exit status of the remote process. Note, that remote system may not support signals concept. In such a case this request will be silently ignored.

Parameters

[in]	channel	The channel to send signal.
[in]	sig	The signal to send (without SIG prefix) (e.g. "TERM" or "KILL").
[in]	core	A boolean to tell if a core was dumped
[in]	errmsg	A CRLF explanation text about the error condition
[in]	lang	The language used in the message (format: RFC 3066)

Returns

SSH_OK on success, SSH_ERROR if an error occurred

ssh_channel_request_send_exit_status()

int ssh_channel_request_send_exit_status	(	ssh_channel	channel,
		int	exit_status )

Send the exit status to the remote process.

Sends the exit status to the remote process (as described in RFC 4254, section 6.10).

Parameters

[in]	channel	The channel to send exit status.
[in]	exit_status	The exit status to send

Returns

SSH_OK on success, SSH_ERROR if an error occurred.

ssh_channel_request_send_signal()

int ssh_channel_request_send_signal	(	ssh_channel	channel,
		const char *	sig )

Send a signal to remote process (as described in RFC 4254, section 6.9).

Sends a signal 'sig' to the remote process. Note, that remote system may not support signals concept. In such a case this request will be silently ignored.

Parameters

[in]	channel	The channel to send signal.
[in]	sig	The signal to send (without SIG prefix) SIGABRT -> ABRT SIGALRM -> ALRM SIGFPE -> FPE SIGHUP -> HUP SIGILL -> ILL SIGINT -> INT SIGKILL -> KILL SIGPIPE -> PIPE SIGQUIT -> QUIT SIGSEGV -> SEGV SIGTERM -> TERM SIGUSR1 -> USR1 SIGUSR2 -> USR2

Returns

SSH_OK on success, SSH_ERROR if an error occurred.

ssh_channel_request_sftp()

int ssh_channel_request_sftp

(

ssh_channel

channel

)

Request sftp subsystem on the channel.

Parameters

[in]

channel

The channel to request the sftp subsystem.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Note

You should use sftp_new() which does this for you.

ssh_channel_request_shell()

int ssh_channel_request_shell

(

ssh_channel

channel

)

Request a shell.

Parameters

[in]

channel

The channel to send the request.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

ssh_channel_request_subsystem()

int ssh_channel_request_subsystem	(	ssh_channel	channel,
		const char *	subsys )

Request a subsystem (for example "sftp").

Parameters

[in]	channel	The channel to send the request.
[in]	subsys	The subsystem to request (for example "sftp").

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

Warning

You normally don't have to call it for sftp, see sftp_new().

ssh_channel_request_x11()

int ssh_channel_request_x11	(	ssh_channel	channel,
		int	single_connection,
		const char *	protocol,
		const char *	cookie,
		int	screen_number )

Sends the "x11-req" channel request over an existing session channel.

This will enable redirecting the display of the remote X11 applications to local X server over a secure tunnel.

Parameters

[in]	channel	An existing session channel where the remote X11 applications are going to be executed.
[in]	single_connection	A boolean to mark only one X11 app will be redirected.
[in]	protocol	A x11 authentication protocol. Pass NULL to use the default value MIT-MAGIC-COOKIE-1.
[in]	cookie	A x11 authentication cookie. Pass NULL to generate a random cookie.
[in]	screen_number	The screen number.

Returns

SSH_OK on success, SSH_ERROR if an error occurred, SSH_AGAIN if in nonblocking mode and call has to be done again.

ssh_channel_select()

int ssh_channel_select	(	ssh_channel *	readchans,
		ssh_channel *	writechans,
		ssh_channel *	exceptchans,
		struct timeval *	timeout )

Act like the standard select(2) on channels.

The list of pointers are then actualized and will only contain pointers to channels that are respectively readable, writable or have an exception to trap.

Parameters

[in]	readchans	A NULL pointer or an array of channel pointers, terminated by a NULL.
[in]	writechans	A NULL pointer or an array of channel pointers, terminated by a NULL.
[in]	exceptchans	A NULL pointer or an array of channel pointers, terminated by a NULL.
[in]	timeout	Timeout as defined by select(2).

Returns

SSH_OK on a successful operation, SSH_EINTR if the select(2) syscall was interrupted, then relaunch the function, or SSH_ERROR on error.

ssh_channel_send_eof()

int ssh_channel_send_eof

(

ssh_channel

channel

)

Send an end of file on the channel.

This doesn't close the channel. You may still read from it but not write.

Parameters

[in]

channel

The channel to send the eof to.

Returns

SSH_OK on success, SSH_ERROR if an error occurred.

Example:

rc = ssh_channel_send_eof(channel);
if (rc == SSH_ERROR) {
    return -1;
}
while(!ssh_channel_is_eof(channel)) {
    rc = ssh_channel_read(channel, buf, sizeof(buf), 0);
    if (rc == SSH_ERROR) {
        return -1;
    }
}
ssh_channel_close(channel);

See also

ssh_channel_close()

ssh_channel_free()

ssh_channel_is_eof()

ssh_channel_set_blocking()

void ssh_channel_set_blocking	(	ssh_channel	channel,
		int	blocking )

Put the channel into blocking or nonblocking mode.

Parameters

[in]	channel	The channel to use.
[in]	blocking	A boolean for blocking or nonblocking.

Warning

A side-effect of this is to put the whole session in non-blocking mode.

See also

ssh_set_blocking()

ssh_channel_set_counter()

void ssh_channel_set_counter	(	ssh_channel	channel,
		ssh_counter	counter )

Set the channel data counter.

struct ssh_counter_struct counter = {
    .in_bytes = 0,
    .out_bytes = 0,
    .in_packets = 0,
    .out_packets = 0
};
 
ssh_channel_set_counter(channel, &counter);

Parameters

[in]	channel	The SSH channel.
[in]	counter	Counter for bytes handled by the channel.

ssh_channel_window_size()

uint32_t ssh_channel_window_size

(

ssh_channel

channel

)

Get the remote window size.

This is the maximum amount of bytes the remote side expects us to send before growing the window again.

Parameters

[in]

channel

The channel to query.

Returns

The remote window size

Warning

A nonzero return value does not guarantee the socket is ready to send that much data. Buffering may happen in the local SSH packet buffer, so beware of really big window sizes.

A zero return value means ssh_channel_write (default settings) will block until the window grows back.

ssh_channel_write()

int ssh_channel_write	(	ssh_channel	channel,
		const void *	data,
		uint32_t	len )

Blocking write on a channel.

Parameters

[in]	channel	The channel to write to.
[in]	data	A pointer to the data to write.
[in]	len	The length of the buffer to write to.

Returns

The number of bytes written, SSH_ERROR on error.

See also

ssh_channel_read()

ssh_channel_write_stderr()

int ssh_channel_write_stderr	(	ssh_channel	channel,
		const void *	data,
		uint32_t	len )

Blocking write on a channel stderr.

Parameters

[in]	channel	The channel to write to.
[in]	data	A pointer to the data to write.
[in]	len	The length of the buffer to write to.

Returns

The number of bytes written, SSH_ERROR on error.

See also

ssh_channel_read()