How to Execute SCP command to transfer files to a target machine

jsulm

@moyin Connect a slot to http://doc.qt.io/qt-5/qprocess.html#errorOccurred and see whether you get any error.

sierdzio

@moyin said in How to Execute SCP command to transfer files to a target machine:

ui->textEdit_Standard_output->setText(StdOut);
ui->textEdit_Standard_output->setText(StdError);

If StdError is empty, then you are effectively overwriting your StdOut. Consider doing this instead:

ui->textEdit_Standard_output->setText(ui->textEdit_Standard_output->text() + StdOut + StdError);

And please use code tags when writing on this forum, it makes reading the code much easier.

moyin

@jsulm i tried this, it does't works.

    connect(&proc, SIGNAL(readyReadStandardError()), this, SLOT(readOutput()));
    connect(&proc, SIGNAL(readyReadStandardOutput()), this, SLOT(readOutput()));
    connect(&proc, SIGNAL(errorOccurred()), this, SLOT(readOutput()));
    proc.startDetached(command,params) ;

And did changes in readoutput() also,

    ui->textEdit_Standard_output->setText(ui->textEdit_Standard_output->toPlainText() + StdOut + StdError);

moyin

@jsulm @sierdzio i'm sharing my .h and .cpp files as well it may help u to understand my problem.

transfer.h

#ifndef TRANSFER_H
#define TRANSFER_H

#include <QDialog>
#include <QProcess>

namespace Ui {
class Transfer;
}

class Transfer : public QDialog
{
    Q_OBJECT

public:
    explicit Transfer(QWidget *parent = 0);
    ~Transfer();

private slots:
    void on_pushButton_Go_clicked();

    void on_pushButton_choosefile_transferTotarget_clicked();

    void on_pushButton_Std_output_clear_clicked();

    void on_checkBox_Show_Password_clicked(bool checked);

    void readOutput() ;

private:
    Ui::Transfer *ui;
    QProcess proc ;
/*
signals:
    void readyReadStandardOutput() ;
    void readyReadStandardError() ;
*/
};

#endif // TRANSFER_H

transfer.cpp

#include "transfer.h"
#include "ui_transfer.h"
#include <sstream>
#include <QProcess>
#include <iostream>
#include <QDebug>
#include <QFileDialog>
#include <QtWidgets>


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

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


void Transfer::on_pushButton_Go_clicked()
{
    //proc = new QProcess() ;
    QString command = "scp" ;
    QString ip = ui->lineEdit_IP_Address->text() ;
    QString username = ui->lineEdit_SSH_username->text() ;
    QString dest_path = ui->lineEdit_TransferToTarget_DestinationFolder->text() ;
    QString source_path = ui->lineEdit_TransferToTarget_SourcePath->text() ;
    std::stringstream s ;
    s << username.toStdString() << "@" << ip.toStdString() << ":" << dest_path.toStdString();
    std::cout << s.str() << std::endl ;
    QStringList params ;
    params.append(source_path) ;
    params.append(QString::fromStdString(s.str())) ;
    qDebug() << params ;
    //    params.append("/home/span51/Desktop/readme.txt");
    //    params.append("spanidea@192.168.1.26:/home/spanidea/test" );
    connect(&proc, SIGNAL(readyReadStandardError()), this, SLOT(readOutput()));
    connect(&proc, SIGNAL(readyReadStandardOutput()), this, SLOT(readOutput()));
    connect(&proc, SIGNAL(errorOccurred()), this, SLOT(readOutput()));
    proc.startDetached(command,params) ;

/*    QString StdOut      =   proc.readAllStandardOutput();  //Reads standard output
    QString StdError    =   proc.readAllStandardError();   //Reads standard error
    std::cout<<"\n Printing the standard output..........\n";
    std::cout<<endl<<StdOut.toStdString();
    std::cout<<"\n Printing the standard error..........\n";
    std::cout<<endl<<StdError.toStdString();
*/
}

void Transfer::on_pushButton_choosefile_transferTotarget_clicked()
{
    QString filepath = QFileDialog::getOpenFileName(this, tr("Transfer file"), "/home","Config_Files(*.c)") ;
    ui->lineEdit_TransferToTarget_SourcePath->setText(filepath);
}

void Transfer::on_pushButton_Std_output_clear_clicked()
{
    ui->textEdit_Standard_output->clear() ;
}

void Transfer::on_checkBox_Show_Password_clicked(bool checked)
{
    if (checked)
        ui->lineEdit_SSH_password->setEchoMode(QLineEdit::Normal);
    else
        ui->lineEdit_SSH_password->setEchoMode(QLineEdit::Password);
}

void Transfer::readOutput()
{
    QString StdOut = proc.readAllStandardOutput();  //Reads standard output
    QString StdError = proc.readAllStandardError(); // Reads standard error

//    ui->textEdit_Standard_output->setText(StdOut);
//    ui->textEdit_Standard_output->setText(StdError);
    ui->textEdit_Standard_output->setText(ui->textEdit_Standard_output->toPlainText() + StdOut + StdError);
}

jsulm

@moyin You again did not read documentation, right? http://doc.qt.io/qt-5/qprocess.html#errorOccurred
Else you would see that errorOccurred() has a parameter.
This connect cannot succeed (you should see a warning at runtime):

connect(&proc, SIGNAL(errorOccurred()), this, SLOT(readOutput()));

You need to use another slot with QProcess::ProcessError error parameter and print out its value.

moyin

@jsulm i can transfer file successfully to the target machine without errors. but wanted to redirect logs whatever (stdout,stderr, etc..,) to textedit. than
why should go for QProcess::ProcessError.

jsulm

@moyin Then check whether these connects actually were successful:

qDebug() << connect(&proc, SIGNAL(readyReadStandardError()), this, SLOT(readOutput()));
qDebug() << connect(&proc, SIGNAL(readyReadStandardOutput()), this, SLOT(readOutput()));

Place a qDebug() in your readOutput() to print something out to see whether the slot is actually called.

moyin

@jsulm i mentioned u already that, while debug if i put break point at or in readoutput() that will stop at break point so it means slot is not getting called.

jsulm

@moyin said in How to Execute SCP command to transfer files to a target machine:

while debug if i put break point at or in readoutput() that will stop at break point so it means slot is not getting called

sorry, I'm confused: if it stops at the break point inside readOutput() then it means that it is actually called.

Try this:

void Transfer::readOutput()
{
    QString StdOut = proc.readAllStandardOutput();  //Reads standard output
    QString StdError = proc.readAllStandardError(); // Reads standard error
    qDebug() << StdOut;
    qDebug() << StdError;
//    ui->textEdit_Standard_output->setText(StdOut);
//    ui->textEdit_Standard_output->setText(StdError);
    ui->textEdit_Standard_output->setText(ui->textEdit_Standard_output->toPlainText() + StdOut + StdError);
}

Do you see anything in Application Output?

moyin

@moyin said in How to Execute SCP command to transfer files to a target machine:

that will stop

sorry correction "that will not stop at breakpoint"

sierdzio

@moyin said in How to Execute SCP command to transfer files to a target machine:

proc.startDetached(command,params) ;

Hm, startDetached() is a static call, so attaching any signals to it won't work, right? Shouldn't start() be used here instead? Just a thought, I have not analysed this code in-depth.

moyin

@jsulm its printing true for both

qDebug() << connect(&proc, SIGNAL(readyReadStandardError()), this, SLOT(readOutput()));
qDebug() << connect(&proc, SIGNAL(readyReadStandardOutput()), this, SLOT(readOutput()));```

qDebug() in readOutput() is not printing any thing.

jsulm

@moyin This is your problem:

proc.startDetached(command,params) ;

startDetached() is a static method! So you start your process, but it is not managed by the proc instance! Use start() instead:

proc.start(command, params);

moyin

@jsulm i tried that also but failed.

jsulm

@moyin In what way failed? Same issue? Slot still not called?

moyin

@jsulm sorry, failed in the sense not able to print the logs into textEdit.

moyin

@jsulm yes slot is not getting called itself.

moyin

@jsulm
Slot still not called? Yes still not called.

jsulm

@moyin Can you post your current code?

JonB

@moyin
I'm lost as to where you're at.

But at least at one point you were told to use QProcess::startDetached() rather than QProcess:start(). I believe (untested by me, as usual, could be putting my neck on the line...) that you cannot properly redirect process input/output and/or get signals for input/output if you run the child process detached...?