data is not appending to the file

Hello all,
i had a problem to access the file operation, when i tried to write something to the file from my GUI(designer file) then it erasing all the data exist in the file and writing only string which i entered in the LineEdit but i want to be append it to the file.
Here is my code

Code:

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#include<QtCore>
#include<QtGui>
#include"ui_dialog1.h"
#include <stdio.h>
 
 
class synopsys : public QDialog,public Ui::dialog1
{
    Q_OBJECT
 
public:
    synopsys()
    {   
        setupUi(this);
       connect(pushButton1, SIGNAL(clicked()), this , SLOT(save()));
       connect(pushButton2, SIGNAL(clicked()), this , SLOT(close()));
 
    }
 
public slots:
 
  void save()
   {
     Qt::CheckState state1,state2,state3,state4;
 
     state1 = checkBox1->checkState();
     state2 = checkBox2->checkState();
     state3 = checkBox3->checkState();
     state4 = checkBox4->checkState();
 
    if(state1 == Qt::Checked)
     { 
       fileName = "/home/window1/synopsys_startup.txt";        
        QFile file(fileName);
        QString str = lineEdit1->text();
 
        const char *ch = str.toLatin1();
        file.open(QIODevice::WriteOnly);
        file.write(ch, qstrlen(ch));        
        file.close();
 
     }
 
 
 
 
     if(state2 == Qt::Checked)
     {   
 
         fileName = "/home/window1/synopsys_startup.txt";
         QFile file(fileName);
      QString str = lineEdit2->text();
 
        const char *ch = str.toLatin1();
        file.open(QIODevice::WriteOnly);
        file.write(ch, qstrlen(ch));        
        file.close();
 
 
    }
 
 
      if(state3 == Qt::Checked)
     {   
 
      fileName = "/home/window1/synopsys_startup.txt";
       QFile file(fileName);
      QString str = lineEdit3->text();
 
        const char *ch = str.toLatin1();
 
        file.open(QIODevice::WriteOnly);
        file.write(ch, qstrlen(ch));        
        file.close();
 
 
 
     }
 
 
      if(state4 == Qt::Checked)
     {   
 
       fileName = "/home/window1/synopsys_startup.txt";
       QFile file(fileName);
     QString str = lineEdit4->text();
 
        const char *ch = str.toLatin1();
        file.open(QIODevice::WriteOnly);
        file.write(ch, qstrlen(ch)); 
        file.close();
 
 
 
     }
 
 
   }
private:
     QString fileName;
 
};
 
int main(int argc, char *argv[])
{
 
     QApplication app(argc,argv);
 
      synopsys *startup = new synopsys;
      startup->show();
 
     return app.exec();
}
 
#include "main.moc"

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any help or suggestion will be much appreciated

You have to open the file in proper mode. "WriteOnly" overwrites the current content of the file. You have to use Append.

thanks i dint observe that