request about scp command (QProcess) using qt

hlowd

I am writing a Windows -> Linux scp file transfer code using qt.

Simple commands such as ipconfig and ping work, but the scp command does not.
When using the ipconfig, ping command, the nRet value is 0, and when using the scp command, the nRet value is -2.
What part can I fix?

ps) This command operates normally in the Windows cmd window.

Below is the full code.
QString command = ui->m_edit->text();

QProcess* process = new QProcess(this);

// command - ipconfig /all
// command - ping xxx.xxx.xxx.xxx
// command - scp [file] [remote name]@[remote ip]:[remote path]

ex) "scp file.ini user@192.168.0.1:\home\user\path"

int nRet = process->execute(command);
//process->start(command);

QByteArray result = process->readAll();

QMessageBox msgbx;
msgbx.setText(result);
msgbx.exec();

jsulm

@hlowd Please format your code properly, it is hard to read.
How does the command look exactly?
Keep in mind that you have to pass the executable and its parameters as extra parameters to QProcess::start as shown in documentation. And please add error handling to see what goes wrong.
Another comment: you're doing readAll() just after executing the command. This is not going to work. Either use waitForReadyRead or (better) connect a slot to readyRead signal and call readAll there.

JonB

@hlowd Your literal C++ string "scp file.ini user@192.168.0.1:\home\user\path" has single backslashes in it.

hlowd

This post is deleted!

hlowd

@JonB
hello.

In the actual code, I entered two backslashes.

Additionally, by using the exeexcute function rather than the start function, no additional parameters were entered, and a response was received immediately.

Only the scp command did not work.

jsulm

@hlowd said in request about scp command (QProcess) using qt:

In the actual code, I entered two backslashes

Please post real code you're using to avoid such confusion.
"Only the scp command did not work" - so does it work now or not?
Did you add error handling as suggested?

hlowd

@hlowd

This is the original source code.
What's wrong?

ps) I added two backslashes to the content, but only one is visible.

//-----------------------------------
// header
//-----------------------------------
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QProcess>

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
MainWindow(QWidget *parent = nullptr);
~MainWindow();
QProcess *m_process;

private slots:
void on_pushButton_clicked();
void readOutput();

private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H

//----------------------------------------
//cpp
//-----------------------------------------
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <qDebug>

MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::on_pushButton_clicked()
{
m_process = new QProcess(this);
QStringList listArguments;

#if 0
QString strParam = "scp";
listArguments << "D:\SVN\Work\test\a.ini user@192.168.1.250:\home\user\SW\";
#else
QString strParam = "ipconfig";
listArguments << "/all";
#endif
connect(m_process, SIGNAL(readyReadStandardError()), this, SLOT(readOutput()));
connect(m_process, SIGNAL(readyReadStandardOutput()), this, SLOT(readOutput()));
connect(m_process, SIGNAL(errorOccurred()), this, SLOT(readOutput()));

m_process->start(strParam, listArguments);
m_process->waitForFinished();

if(m_process)
    delete m_process;

}

void MainWindow::readOutput()
{
QString StdOut = m_process->readAllStandardOutput();
QString StdError = m_process->readAllStandardError();
QString StdError1 = m_process->errorString();
qDebug() << "======================================\n";
qDebug() << StdOut;
qDebug() << StdError;
qDebug() << StdError1;
qDebug() << "======================================\n";
}

jsulm

@hlowd said in request about scp command (QProcess) using qt:

listArguments << "D:\SVN\Work\test\a.ini user@192.168.1.250:\home\user\SW";

Is this really your real code?!
You again have single back-slashes.
And why do you use back-slashes for paths on Linux side?
Also that line should be:

listArguments << "D:\\SVN\\Work\\test\\a.ini" <<  "user@192.168.1.250:/home/user/SW/";

And please format you code properly.

hlowd

@hlowd

I entered two words in the post, but only one is displayed on the screen...

jsulm

@hlowd said in request about scp command (QProcess) using qt:

I entered two words in the post, but only one is displayed on the screen...

Use code tags properly, then it will be shown correctly

hlowd

@hlowd

listArguments << "D:\\SVN\\Work\\test\\a.ini" << "user@192.168.1.250:/home/user/SW/";

Even though I entered it like this, it is the same.
The response from start comes immediately, but the readOutput function is not called.

jsulm

@hlowd said in request about scp command (QProcess) using qt:

but the readOutput function is not called

Probably because you're deleting m_process right after waitForFinished.
Are you sure scp.exe command is found?
Try with an absolute path to scp.exe to make sure it is actually found.

hlowd

@hlowd

The symptom is the same even if delete is not called.

If it is a command instruction rather than a code, the instruction will be executed normally.
The file is moved normally. (Windows -> Linux)

jsulm

@hlowd Again: try with absolute path to scp.exe

hlowd

@hlowd
There are files in that path.

C:\Windows\WinSxS\amd64_openssh-common-components-onecore_31bf3856ad364e35_10.0.22621.1_none_1e3c4880a37d88bb

scp.exe
ssh-add.exe
ssh-agent.exe
ssh-keygen.exe

// new code

QString strParam = "C:\\Windows\\WinSxS\\amd64_openssh-common-components-onecore_31bf3856ad364e35_10.0.22621.1_none_1e3c4880a37d88bb\\scp.exe";

// error message

"CreateProcessW failed error:2 posix_spawn: No such file or directory"

JonB

@hlowd
If you want help on this, at least for my part, please make the effort to enclose your code blocks and literal extracts in the forums block quotes (</> button) as we have asked several times. It does not require much effort on your side.

By now you should be trying a command of scp, nothing else, no arguments, to verify that (a) it is found and can be run and (b) you can successfully read any output from it, e.g. presumably a "usage" message in this case.

jsulm

@hlowd said in request about scp command (QProcess) using qt:

Can I do it this way?

Yes, just try.
I would also execute scp using this absolute path in a terminal to make sure it works.

hlowd

@jsulm

There are files in that path.

C:\Windows\WinSxS\amd64_openssh-common-components-onecore_31bf3856ad364e35_10.0.22621.1_none_1e3c4880a37d88bb

scp.exe
ssh-add.exe
ssh-agent.exe
ssh-keygen.exe

// new code

QString strParam = "C:\\Windows\\WinSxS\\amd64_openssh-common-components-onecore_31bf3856ad364e35_10.0.22621.1_none_1e3c4880a37d88bb\\scp.exe";

// error message

"CreateProcessW failed error:2 posix_spawn: No such file or directory"

The same error occurs in the command prompt.

JonB

@hlowd
I am not a total Windows expert, but I did not think you should ever attempt to run anything in the WinSxS area? You should be running the scp which is on your PATH (presumably).

jsulm

@hlowd Did scp executable ever work for you in terminal? The path where it is located looks strange, don't know from where it comes. On my machine I have it here: c:\windows\System32\OpenSSH\scp.exe

You can check where your scp.exe is located using this command:

where scp