Weird behavior of QProcess and multiple qoutes

[Konstantin Tokarev]

Use QProcess::execute overload with QStringList arguments

[mrjj]

Hi
In other words, do not append to one string

String program = "wpa_cli";
QStringList arguments;
arguments <<"set_network"<< "0" << "psk" << "12345" ;

QProcess *myProcess = new QProcess(parent);
myProcess->start(program, arguments);

Also to help yourself, at least hook up to
http://doc.qt.io/qt-5/qprocess.html#errorOccurred

[Manta Ray]

Hello,

I tried to use execute with argument list and my results were the same as earlier.
I've added connection to signal errorOccurred() but this signal was not emited.

My code is here:

    QString program = "wpa_cli";
    QStringList arguments;
    QProcess * wpacli = new QProcess();

    connect(wpacli, SIGNAL(errorOccurred(QProcess::ProcessError )), this, SLOT(onError(QProcess::ProcessError)));

    arguments << "remove_network" << "all";
    qDebug() << arguments;
    wpacli->execute(program, arguments);

    arguments.clear();
    arguments << "add_network";
    qDebug() << arguments;
    wpacli->execute(program, arguments);

    arguments.clear();
    arguments << "set_network" << "0" << "ssid" << id.toUtf8().toHex();
    qDebug() << arguments;
    wpacli->execute(program, arguments);

    arguments.clear();
    arguments << "set_network" << "0" << "psk" << pwd;
    qDebug() << arguments;
    wpacli->execute(program, arguments);

    arguments.clear();
    arguments << "enable_network" << "0";
    qDebug() << arguments;
    wpacli->execute(program, arguments);

    arguments.clear();
    arguments << "select_network" << "0";
    qDebug() << arguments;
    wpacli->execute(program, arguments);

    arguments.clear();
    arguments << "save_config";
    qDebug() << arguments;
    wpacli->execute(program, arguments);

In onError() slot I've printed some logs:

qDebug() << Q_FUNC_INFO;

    QString errorStr;

    switch(error) {
    case QProcess::FailedToStart: errorStr = "QProcess::FailedToStart"; break;
    case QProcess::Crashed: errorStr = "QProcess::Crashed"; break;
    case QProcess::Timedout: errorStr = "QProcess::Timedout"; break;
    case QProcess::WriteError: errorStr = "QProcess::WriteError"; break;
    case QProcess::ReadError: errorStr = "QProcess::ReadError"; break;
    case QProcess::UnknownError: errorStr = "QProcess::UnknownError"; break;
    }

    qDebug() << errorStr;

In console I can see the next results:

("remove_network", "all")
Selected interface 'wlan0'
OK
("add_network")
Selected interface 'wlan0'
0
("set_network", "0", "ssid", "416e64726f69644150")
Selected interface 'wlan0'
OK
("set_network", "0", "psk", "12345678")
Selected interface 'wlan0'
FAIL
("enable_network", "0")
Selected interface 'wlan0'
OK
("select_network", "0")
Selected interface 'wlan0'
OK
("save_config")
Selected interface 'wlan0'
OK

I'm not sure that using of argument list is good idea, because wpa_cli required to get password in multiple quotes: '""'.

Do you have other ideas?

[jsulm]

@Manta-Ray
Then just do

arguments << "set_network" << "0" << "psk" << "\"" + pwd + "\"";

[Manta Ray]

@jsulm
Ok, added

    arguments.clear();
    arguments << "set_network" << "0" << "psk" << "'\"" << pwd << "\"'";
    qDebug() << arguments;
    wpacli->execute(program, arguments);

and got the same result:

("set_network", "0", "psk", "'\"", "12345678", "\"'")
Selected interface 'wlan0'
FAIL

[jsulm]

@Manta-Ray Please read again what I wrote and compare it to what you did.

[Manta Ray]

Wow!
It works! Thanks a lot!
Thanks!
Thanks!
Thanks!

Can you, please, explain me, what's the magic is going here?

[Konstantin Tokarev]

@Manta-Ray You need to pass 4 arguments to wpa_cli:

set_network, 0, psk, "12345678"

instead you passed 6

set_network, 0, psk, ", 12345678, "

[jsulm]

@Manta-Ray No magic. You simply put both " as own parameters:

arguments << "set_network" << "0" << "psk" << "'\"" << pwd << "\"'";

see here:

("set_network", "0", "psk", "'\"", "12345678", "\"'")

Instead you need to put your password as one string with leading and trailing ", like here:

arguments << "set_network" << "0" << "psk" << "\"" + pwd + "\"";

[Manta Ray]

Ahaaaa, Thanks you guys a lot!!!!!!
I really appreciate you!!!!

[Guanhong]

@Manta-Ray
I met the same issue and it failed.
Could you show me your codes or tell me what's wrong with my codes following, thanks

            QString strSSID = "12345678"
            QString program = "wpa_cli";
            QStringList arguments;      
            arguments << "-i" << "wlan0" << "set_network" << "0"<< "ssid" << "'\"" << strSSID << "\"'";  
            QProcess prcsWlan4;
            prcsWlan4.start(program, arguments);
            prcsWlan4.waitForFinished(-1);  
            QString strResult4 = prcsWlan4.readAllStandardOutput();

the result strResult4 is FAIL

[Christian Ehrlicher]

@Guanhong said in Weird behavior of QProcess and multiple qoutes:

<< "'"" << strSSID << ""'";

Why do you quote this? It's not needed at all - every value in the QStringList is passed as one parameter to your app. That's the reason why you should not use the other call - to avoid useless and wrong quotes.

[Guanhong]

@Christian-Ehrlicher
thank you for your swift reply

actually in my project, strSSID is a variable, it is delivered by other parameters, here I just made it a constant for convenience.

I changed
arguments << "-i" << "wlan0" << "set_network" << "0"<< "ssid" << "'"" << strSSID << ""'";
to
arguments << "-i" << "wlan0" << "set_network" << "0"<< "ssid" << "'"" + strSSID + ""'";

it still FAILed.
could you help me?

[jsulm]

@Guanhong Please read once more what @Christian-Ehrlicher wrote. Your change is NOT what he wrote...

[Guanhong]

@jsulm thank you.
I think quotes are necessary, because there is a single quote outside a double quote.
I need to process the following command by QProcess, could you show me how?
pa_cli -i wlan0 set_network 1 ssid '"hima24g"'

[Christian Ehrlicher]

Again: there is no need to quote an argument when using QProcess::start() with QStringList - they are only needed on the command line so bash/cmd.exe/whatever knows what a single argument is! Your ssid is hima24g and not "hima24g" or 'hima24g' ... or?

[Guanhong]

@Christian-Ehrlicher
Even if there are single quotes and double quotes in the command, is there no need to add quotes? I looked at earlier replies, it seems that quotes are need.

I just removed quotes and changed my codes to
arguments << "-i" << "wlan0" << "set_network" << "0"<< "ssid" << strSSID ;
FAILed too.

[jsulm]

@Guanhong Then add proper error handling and also read from std error of your process to see whether it prints any errors.

[Guanhong]

@jsulm
QString strResult4 = prcsWlan4.readAllStandardOutput();
strResult4 is FAIL

[jsulm]

@Guanhong said in Weird behavior of QProcess and multiple qoutes:

readAllStandardOutput()

I was talking about std ERROR (https://doc.qt.io/qt-5/qprocess.html#readAllStandardError)...