Qt, implementing an SFTP client

[SPlatten]

@jsulm, having re-written the code, my slot never gets called, meaning the signal can't be emitted.

[JonB]

@splatten
Which is why I said to use https://doc.qt.io/qt-5/qprocess.html#readyReadStandardOutput for better/proper behaviour....

There is a wrinkle you may have to face. It is possible that your command-line sftp executable will not prompt for password if it detects that the user is not in an interactive terminal (stdin). E.g. its code may quite possibly have

if (isatty(0))
    prompt_for_password();
else
   // do not prompt for password

That will be problematic if it is the case. You could try in a terminal sftp < /dev/null or sftp < file: if that does not still prompt for password you have a (potential) problem....

[SPlatten]

@JonB , would this help:

    mpSFTP->setProcessChannelMode(QProcess::MergedChannels);

[JonB]

@splatten
Help what, in what way? If the sftp requires a terminal stdin for password prompt, then no, if, say, you have a purely interactive Qt application. You can try it. But the first thing to test is whether your sftp behaves differently if its stdin is not attached to a terminal?

[SPlatten]

Now the slot gets called and in my slot I have:

    qDebug() << "readAllStandardOutput:";
    qDebug() << mpSFTP->readAllStandardOutput();
    qDebug() << "readChannel:";
    qDebug() << mpSFTP->readChannel();

In the output I see:

    readAllStandardOutput:
    "ssh_askpass: exec(/usr/local/libexec/ssh-askpass): No such file or directory
    "
    readChannel:
    0

[jsulm]

@splatten What happens if you execute exact same command manually in a terminal?
Also connect a slot to the error signal from QProcess and check whether you get any errors.

[SPlatten]

@jsulm , When I execute "sftp" with the command line arguments, it works without any issues.

[JonB]

@splatten
As I have said before, so last time now:

ssh_askpass: exec(/usr/local/libexec/ssh-askpass): No such file or directory

This is because your sftp is not willing/able to access stdin to get a password. Try what I said about seeing how your sftp behaves with input/output redirected when run from a terminal. I will not comment again, and leave it to you.

[SPlatten]

ssh_askpass is not available on this linux distribution.

[JonB]

@splatten
Yes, so you can't use it.

[SPlatten]

@JonB, I've tried everything you have suggested so far and not been able to make any progress due to either incorrect syntax or missing commands.

[JonB]

@splatten
I am suggesting your sftp client will not work to prompt for a password if you do not run it from a terminal. It will not work when you try redirection from a parent process like Qt.

The man page for my sftp under Ubuntu at least is pretty explicit about requiring either an "interactive" session for authentication, or must use ssh facilities for non-password authentication. Does your system have man sftp for you to read through?