How to communicate with external programs?

[deekayt]

Forked from: http://www.qtcentre.org/forum/f-qt-designer-3/t-customslots-in-qt4-4108.html

THANK YOU VERY MUCH
I WAS ABLE TO RUN THE APPLICATION ATLAST ....

I need to first start some processes fromthe mother application ( dialog) on the clickof the pushbutton. I tried the Q process but it didnot work out.Then I resorted to System call . This I know is not a clean process but just to check the slot thing I have put this now.

my code snippet is as

steg::steg(QWidget *parent)
: QDialog(parent)
{
ui.setupUi(this);
connect(ui.okButton, SIGNAL(clicked()), this, SLOT(test()));
connect(ui.cancelButton, SIGNAL(clicked()), this, SLOT(open_file()));
}

void steg::test()
{
system("e:\"\"\"stego.jpg");
}

you see above the okbutton on being clicked gives signal to slot test() .test() function has system call to launch picture viewer to show the file stego.jpg.
Canyou suggest a better method to do this task.

Secondly I need to create , open , write , execute and close the file very often in my program on the click of buttons.

i tried the following snippets


void steg::writeinfile()
{
char eog_comand[]= "eog";
char space[]= " ";
FILE *fp;
fp = fopen ("e:\"\"\"trial.txt", "w+");
fputs (eog_comand,fp);
fputs (space,fp);
fclose(fp);
}
this is simple c code .But when i run the program it crashes.
I tried Qfile commands

void steg::writeinfile()
{
QFile file;
file.setFileName("e:\"\"\"trial.txt");
file.open(QIODevice::WriteOnly);
file.write(msg, qstrlen(msg)); // write to stderr
file.close();
}
But that alsodoesnot work
Someguidance please.

[jacek]

Canyou suggest a better method to do this task.
Use QProcess::startDetached(). This should work:

QProcess::startDetached( "start", QStringList() << "something.jpg" );


Secondly I need to create , open , write , execute and close the file very often in my program on the click of buttons.
Use QProcess.

Please, don't ask unrelated questions in one thread --- open new thread for new issues. Also, please, use [ code ] tags for code snippets and [ quote ] tags only for quotes.

[deekayt]

Suppose I need to start any program which is there available in my computer by click of button from my designed form.
I have created a QDialog and put a pushbutton. Then through a private slot I am trying to access the program ( or launch the program , say windows media player which is “wmplayer” ) which ideally should be detached from the parent program which I launch initially .
I have tried QProcess with various combinations but it is not working.
Where as if you type wmplayer on the command line run window the program runs.
Interestingly when I type “cmd” that is the command line window it runs from myprogram and the command prompt for DOS opens up .But this is theonlyone which runs.

The code is as

steg::steg(QWidget *parent)
: QDialog(parent)
{
ui.setupUi(this);
connect(ui.showdatafile, SIGNAL(clicked()), this, SLOT(showdatafile()));

}

void steg::showdatafile()
{
QProcess *myProcess ;
QString program = "wmplayer";
myProcess->startDetached(program);
}
I have tried your suggestion also


QProcess::startDetached( "start", QStringList() << "something.jpg" );

the code doesnot give any error.But when I click the button to launch it just doesnot run at all
could you suggest some solution

[patrik08]

Have a look on
http://www.qtcentre.org/forum/f-qt-programming-2/t-qdesktopservices-open-url-local-file-pdf-or-doc-4178.html

running only on mac & win .. linux dont have system urlhandler or file ecc...
only webbsiteurl on the new QDesktopServices qt4.2

[jacek]

myProcess->startDetached(program);
QProcess::startDetached is a static method, you don't need any object to invoke it.

How about this?

QProcess::startDetached( "C:/full/path/to/wmplayer", QStringList() );
Also check the return value.

[deekayt]

I need to execute a DOS executable program with click of a button in my form designed in QT 4 ( windows)
This DOS executable is an exe file and takes certain switches and filenames (which I supply through lineedits)
Till now I was resorting to using .bat (executable) file where I used to write the whole command as I would have typed on the command prompt and then I execute that bat file with the help of system command . All this I do under a user defined function which is connected to a private slot activated by the click of a button.
This does work but is not correct and also gives bugs sometimes.
I tried the Qprocess thing but somehow it doesnot work.
I tried to adopt the code ( given by patrick08) which is used for seeing the file from the form as below .It does work for seeing file in it’s associated program.

The code for seeing ( say image ) file

steg::steg(QWidget *parent)
: QDialog(parent)
{
ui.setupUi(this);
connect(ui.showimagefile, SIGNAL(clicked()), this, SLOT(showimagefile()));
}
void steg::showimagefile()

{
QProcess p1;
QStringList s1;
s1 << "url.dll,FileProtocolHandler" << ui.imagelineEdit->text() ;
p1.startDetached(QString("rundll32.exe") , s1 );
}
I adopted this for the exe program burp.exe with switches as -e filename1 filename2 -k keystring . The code I tried is as below


steg::steg(QWidget *parent)
: QDialog(parent)
{
ui.setupUi(this);
connect(ui.encryptpushButton, SIGNAL(clicked()), this, SLOT(encrypt()));
}


void steg::encrypt()
{
char encrypt_comand[]= " -e ";
char key_comand[]= "-k=";
char space[]= " ";

QProcess p3;
QStringList s3;
s3 << space<< encrypt_comand<<ui.datalineEdit->text() <<space<< "coded.txt"<<space<<key_comand <<ui.passphraselineEdit->text();
p3.startDetached(QString("burp.exe") , s3 );
}
But it doesnot work.
Your comments and guidance please.

[wysota]

I tried the Qprocess thing but somehow it doesnot work.

How did you invoke QProcess? Can we see the code?

[jacek]

char encrypt_comand[]= " -e ";
char key_comand[]= "-k=";
char space[]= " ";

QProcess p3;
QStringList s3;
s3 << space<< encrypt_comand<<ui.datalineEdit->text() <<space<< "coded.txt"<<space<<key_comand <<ui.passphraselineEdit->text();
p3.startDetached(QString("burp.exe") , s3 );
}
Each entry in the string list "s3" should represent a single argument, so you shouldn't add any spaces, especially inside encrypt_command.

It should be something like (note the + after key_command):

char encrypt_comand[]= "-e";
char key_comand[]= "-k=";

QStringList s3;
s3 << encrypt_comand << ui.datalineEdit->text() << "coded.txt" << ( key_comand + ui.passphraselineEdit->text() );
QProcess::startDetached( QString("/full/path/to/burp.exe"), s3 );
Make sure you specify full path to the executable, if it isn't in the current working directory (you might find QCoreApplication::applicationDirPath() useful).

And, for the second time, QProcess::startDetached() is a static method, so you shouldn't create any QProcess instances to invoke it.

Edit: Please, don't ask the same question in more than one thread. Threads merged.