int libssh2_channel_setenv_ex(LIBSSH2_CHANNEL *channel, char *varname, unsigned int varname_len, const char *value, unsigned int value_len);
int libssh2_channel_setenv(LIBSSH2_CHANNEL *channel, char *varname, const char *value);
varname - Name of environment variable to set on the remote channel instance.
varname_len - Length of passed varname parameter.
value - Value to set varname to.
value_len - Length of value parameter.
Set an environment variable in the remote channel's process space. Note that this does not make sense for all channel types and may be ignored by the server despite returning success.
LIBSSH2_ERROR_SOCKET_SEND - Unable to send data on socket.
LIBSSH2_ERROR_CHANNEL_REQUEST_DENIED -