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SFTP Append doesn't work [?] #390
Description
I've been trying to append text to the end of the file with OpenMode.APPEND, but no luck so far. It seems to ignore this flag and just uses the offset. If I set the offsets (both file & off) to 0, then it'll rewrite the file. How do I go about appending text to the end of the file WITHOUT offsets and ONLY with OpenMode.APPEND, if it's possible?
Here's how I'm trying to do it
String fileName = "test_write_continuously.txt";
String filePath = HOME_FOLDER + "/" + fileName;
String initialText = "This is initial text of the file. ";
byte[] bytes = initialText.getBytes();
RemoteFile writeInitial = sftpClient.open(filePath, new HashSet<>(Arrays.asList(OpenMode.WRITE, OpenMode.CREAT)));
writeInitial.write(0, bytes, 0, bytes.length);
writeInitial.close();
String appendText = "This is the continuation text that should be appended after initial. ";
byte[] appendTextBytes = appendText.getBytes();
RemoteFile writeAppend = sftpClient.open(filePath, new HashSet<>(Arrays.asList(OpenMode.WRITE, OpenMode.APPEND)));
writeAppend.write(0, appendTextBytes, 0, appendTextBytes.length);
writeAppend.close();
RemoteFile readContent = sftpClient.open(filePath, new HashSet<>(Arrays.asList(OpenMode.READ)));
byte[] readBytes = new byte[bytes.length + appendTextBytes.length];
readContent.read(0, readBytes, 0, readBytes.length);
String readString = new String(readBytes);
readContent.close();
assertEquals(initialText + appendText, readString);
What I want to achieve: continuously write to the end of the file, pretty much real-time logging on a remote server through ssh, and I need the data to be consistent and in order. You think it's possible to achieve? So far I've been having file rewrites
Activity
IgnatBeresnev commentedon Dec 27, 2017
Maybe the problem is that we shouldn't put file offset if APPEND is specified?
hierynomus commentedon Dec 28, 2017
According to the specifications, the
fileOffsetfield is required and cannot be omitted. When a file is opened withSSH_FXF_APPEND, the sftp server should ignore the offset flag and append to the file.Which SFTP server are you using?
hierynomus commentedon Dec 28, 2017
I've added an integration test in 0f67fa2 which shows that it should work with your exact scenario. This is as far as I can see really a bug in your SFTP server.
IgnatBeresnev commentedon Jan 9, 2018
You seem to be right. The problem is reproduced only on the server that uses OpenSSH 5.3. However, another server with OpenSSH 7.4 is passing tests just fine.
Thanks. Didn't even think that could be a problem
hierynomus commentedon Jan 9, 2018
Thanks for confirming! Good to know that OpenSSH had a bug ;).
merge (#1)