use Net::SFTP;
use Net::SFTP::Util;
use Net::SFTP::Attributes;
use Net::SFTP::Constants qw( :flags );

# ...

#///////////////////////////////////////////////////////////////
sub sftp_connect {
    my( $hostname ) = @_;
    my $sftp = Net::SFTP->new( 
        $hostname, 
        user     => $cfg{sftp_username}, 
        password => $cfg{sftp_password},
        ) || die "Could not login to the remote server";
    return $sftp;
    }        

#///////////////////////////////////////////////////////////////
sub sftp_ls_match {
    my( $sftp, $path, $filename_to_match ) = @_;
    my $file_ref;
    my @files =  @{ $sftp->ls( $path ) || die "Could not sftp->ls($pat
+h)" } ;
    FIND_FILE:
    foreach my $ref ( @files  ) {
        next FIND_FILE unless $ref->{filename} eq $filename_to_match;
        $file_ref = $ref;
        last FIND_FILE;
        }
    return $file_ref;
    }
    
        
#///////////////////////////////////////////////////////////////
sub sftp_data_file_new {
    my( $hostname, $data ) = @_;
    my( $attr_ref, $flags, $offset );
    
    my $sftp      =  sftp_connect(  $hostname ) || die "Could not sftp
+_connect($hostname)";
    my $file_ref  =  sftp_ls_match( $sftp, $cfg{sftp_path}, $cfg{data_
+file_new} );
    
    # CASE: File exists
    if( defined $file_ref ) {
        # NOTE: $sftp->ls does not follow symbolic links. Thus the mti
+me from 
        # $file_ref->{a} could be for a symbolic link (where mtime wil
+l rarely 
        # change). Thus we use the output from do_stat which does foll
+ow sym links
        $attr_ref  =  $sftp->do_stat( "$cfg{sftp_path}/$cfg{data_file_
+new}" );
        $offset    =  $attr_ref->{size};
        $flags     =  SSH2_FXF_WRITE | SSH2_FXF_APPEND;
        }
    # CASE: File does *NOT* exist
    else {
        $attr_ref  =  new Net::SFTP::Attributes;
        $offset    =  0;
        $flags     =  SSH2_FXF_WRITE | SSH2_FXF_CREAT;
        }
    
    my $handle = $sftp->do_open( "$cfg{sftp_path}/$cfg{data_file_new}"
+,  $flags,  $attr_ref);
    $sftp->do_write(  $handle, $offset, $data  );
    $sftp->do_close(  $handle );

    # To get the new mtime we need to stat the file.
    $attr_ref = $sftp->do_stat( "$cfg{sftp_path}/$cfg{data_file_new}" 
+);

    # ...
    
    return;
    }
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