#include <libssh2.h> ssize_t libssh2_channel_write_ex(LIBSSH2_CHANNEL *channel, int stream_id, char *buf, size_t buflen);
Write data to a channel stream. All channel streams have one standard I/O substream (stream_id == 0), and may have up to 2^32 extended data streams as identified by the selected stream_id. The SSH2 protocol currently defines a stream ID of 1 to be the stderr substream.
channel - active channel stream to write to.
stream_id - substream ID number (e.g. 0 or SSH_EXTENDED_DATA_STDERR)
buf - pointer to buffer to write
buflen - size of the data to write
libssh2_channel_write(3) and libssh2_channel_write_stderr(3) are convenience macros for this function.
libssh2_channel_write_ex(3) will use as much as possible of the buffer and put it into a single SSH protocol packet. This means that to get maximum performance when sending larger files, you should try to always pass in at least 32K of data to this function.
Actual number of bytes written or negative on failure. LIBSSH2_ERROR_EAGAIN when it would otherwise block. While LIBSSH2_ERROR_EAGAIN is a negative number, it isn't really a failure per se.
LIBSSH2_ERROR_ALLOC - An internal memory allocation call failed.
LIBSSH2_ERROR_SOCKET_SEND - Unable to send data on socket.
LIBSSH2_ERROR_CHANNEL_CLOSED - The channel has been closed.
LIBSSH2_ERROR_CHANNEL_EOF_SENT - The channel has been requested to be closed.
libssh2_channel_set_blocking(3), libssh2_channel_write(3), libssh2_channel_write_stderr(3).