libssh2\_channel\_write\_ex(3) libssh2 libssh2\_channel\_write\_ex(3) # [NAME](#NAME) libssh2\_channel\_write\_ex - write data to a channel stream blocking # [SYNOPSIS](#SYNOPSIS) ``` #include ssize_t libssh2_channel_write_ex(LIBSSH2_CHANNEL *channel, int stream_id, char *buf, size_t buflen); ``` # [DESCRIPTION](#DESCRIPTION) 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)*](/man/os/libssh2/libssh2_channel_write.3) and [*libssh2\_channel\_write\_stderr(3)*](/man/os/libssh2/libssh2_channel_write_stderr.3) are convenience macros for this function. [*libssh2\_channel\_write\_ex(3)*](/man/os/libssh2/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. # [RETURN VALUE](#RETURN_VALUE) 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 is not really a failure per se. # [ERRORS](#ERRORS) *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 *LIBSSH2\_ERROR\_BAD\_USE* - This can be returned if you ignored a previous return for LIBSSH2\_ERROR\_EAGAIN and rather than sending the original buffer with the original size, you sent a new buffer with a different size. closed. # [SEE ALSO](#SEE_ALSO) [**libssh2\_channel\_open\_ex(3)**](/man/os/libssh2/libssh2_channel_open_ex.3) [**libssh2\_channel\_read\_ex(3)**](/man/os/libssh2/libssh2_channel_read_ex.3) 1 Jun 2007 libssh2 0.15 --- Document: libssh2_channel_write_ex(3) from libssh2 1.11.1-r10 (Chainguard OS) Source: https://github.com/libssh2/libssh2.git