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libssh2_sftp_write(3)           libssh2 manual           libssh2_sftp_write(3)




NAME

       libssh2_sftp_write - write SFTP data


SYNOPSIS

       #include <libssh2.h>
       #include <libssh2_sftp.h>

       ssize_t libssh2_sftp_write(LIBSSH2_SFTP_HANDLE *handle,
                                  const char *buffer,
                                  size_t count);


DESCRIPTION

       libssh2_sftp_write(3)  writes  a block of data to the SFTP server. This
       method is modeled after the POSIX write() function and  uses  the  same
       calling semantics.

       handle - SFTP file handle as returned by libssh2_sftp_open_ex(3).

       buffer - points to the data to send off.

       count - Number of bytes from 'buffer' to write. Note that it may not be
       possible to write all bytes as requested.

       libssh2_sftp_handle(3) will use as much as possible of the  buffer  and
       put it into a single SFTP protocol packet. This means that to get maxi-
       mum performance when sending larger files, you  should  try  to  always
       pass in at least 32K of data to this function.



WRITE AHEAD

       Starting  in  libssh2 version 1.2.8, the default behavior of libssh2 is
       to create several smaller outgoing packets for all  data  you  pass  to
       this function and it will return a positive number as soon as the first
       packet is acknowledged from the server.

       This has the effect that sometimes more data  has  been  sent  off  but
       isn't  acked  yet when this function returns, and when this function is
       subsequently called again to write more data, libssh2 will  immediately
       figure out that the data is already received remotely.

       In  most  normal  situation  this should not cause any problems, but it
       should be noted that if you've once  called  libssh2_sftp_write()  with
       data  and  it returns short, you MUST still assume that the rest of the
       data might've been cached so you need to make sure you don't alter that
       data  and  think that the version you have in your next function invoke
       will be detected or used.

       The reason for this funny behavior is that SFTP can only send 32K  data
       in  each  packet and it gets all packets acked individually. This means
       we cannot use a simple serial approach if we want to reach high perfor-
       mance even on high latency connections. And we want that.


RETURN VALUE

       Actual number of bytes written or negative on failure.

       If  used  in non-blocking mode, it returns LIBSSH2_ERROR_EAGAIN when it
       would otherwise block. While LIBSSH2_ERROR_EAGAIN is a negative number,
       it isn't really a failure per se.

       If this function returns 0 (zero) it should not be considered an error,
       but simply that there was no error but yet no payload data got sent  to
       the other end.


ERRORS

       LIBSSH2_ERROR_ALLOC -  An internal memory allocation call failed.

       LIBSSH2_ERROR_SOCKET_SEND - Unable to send data on socket.

       LIBSSH2_ERROR_SOCKET_TIMEOUT -

       LIBSSH2_ERROR_SFTP_PROTOCOL  -  An  invalid  SFTP protocol response was
       received on the socket, or an SFTP operation caused an errorcode to  be
       returned by the server.


SEE ALSO

       libssh2_sftp_open_ex(3)



libssh2 0.15                      1 Jun 2007             libssh2_sftp_write(3)

libssh2 1.7.0 - Generated Thu May 26 06:02:08 CDT 2016
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