read ( buffer, size )

write ( buffer )

The "libssh2_sftp_write" function wrapped by this method has a complex and quite difficult (if not impossible at all) to use API. It tries to hide the packet pipelining being done under the hood in order to attain decent throughput.

Net::SSH2 can not hide that complexity without negatively affecting the transmission speed so it provides just a thin wrapper for that library function.

An excerpt from "libssh2_sftp_write" manual page follows:

  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 performance even on high latency connections. And we want that.

This is an example of simple file uploading

    use constant BUF_SIZE => 128*1024;
    
    my $sftp = $ssh2->sftp;
    open my $fh, '<', '/tmp/doc.txt';
    my $sf = $sftp->open('doc.txt', O_CREAT|O_WRONLY|O_TRUNC);
    
    my $buf;
    while (sysread($fh, $buf, BUF_SIZE)) {
        while (length $buf) {
            my $rc = $sf->write($buf);
            if (!defined($rc)) {
                $sftp->die_with_error('write error');
            }
            # Remove transferred data from the buffer.
            substr($buf, 0, $rc) = '';
        }
    }

stat

setstat ( key, value... )

seek ( offset )

tell