I'm programming in Qt, but I'm more accustomed to PHP.
So with that in mind, how do I 'echo' or 'print' out the contents of a QStringList or QString to ensure the contents are as expected?
I'm building a GUI application. Is there anyway to print the contents?
Obviously in PHP, you can print_r on an array, is there anything similar for a QStringList?
And echo a variable, again, anything similar to QString?
I can provide code if needs be.
Thanks.
main.cpp
#include <QStringList>
#include <QDebug>
int main()
{
QStringList myStringList{"Foo", "Bar", "Baz"};
qDebug() << myStringList;
QString myString = "Hello World!";
qDebug() << myString;
return 0;
}
main.pro
TEMPLATE = app
TARGET = print-qstringlist
QT = core
CONFIG += c++11
SOURCES += main.cpp
Build and Run
qmake && (n)make
Output
("Foo", "Bar", "Baz")
"Hello World!"
If you need to drop the noisy brackets and double quotes generated by qDebug, you are free to either use QTextStream with custom printing or simply fall back to the standard cout with custom printing.
I have the code below. I am using Qt_5_0_2_MSVC2012_64bit-Release. I am not able to read the file. I get the debug error message of "Cannot open file for reading".There is some problem for me with resource files. Any idea how I can fix it? Thanks!
#include <QCoreApplication>
#include <QFile>
#include <QString>
#include <QDebug>
#include <QTextStream>
#include <QResource>
#include <QIODevice>
void Read(QString Filename){
QFile mFile(Filename);
if(!mFile.open(QFile::ReadOnly | QFile::Text)){
qDebug() << "could not open file for read";
return;
}
QTextStream in(&mFile);
QString mText = in.readAll();
qDebug() << mText;
mFile.close();
}
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
Read(":/MyFiles/myfile.txt");
return a.exec();
}
I had same problem. The Error string was "Unknown error". Solution was to add INCLUDEPATH += . from #gatto's answer and run commands from menu:
1. Build -> Clean all
2. Build -> Run qmake
3. Build -> Rebuild All
test.pro:
TEMPLATE = app
TARGET = test
INCLUDEPATH += .
# Input
SOURCES += main.cpp
RESOURCES += test.qrc
test.qrc:
<!DOCTYPE RCC><RCC version="1.0">
<qresource>
<file>MyFiles/myfile.txt</file>
</qresource>
</RCC>
main.cpp is from your question. Works fine.
That said, if you still have the problem, you should post minimal Qt project (including .pro and .qrc files), that has the error.
I'm trying to do something very simple, I just want to print my native language, pt-br in Windows Console.
IDE Creator
I created a new project->other->Qt Console Application the I put it in my main.cpp file:
#include <QCoreApplication>
#include <QDebug>
#include <QTextCodec>
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
qDebug() << "aeiou áéíóú";
std::cout << "aeiou áéíóú" << endl;
return 0;
}
here is what I got:
C:\Users\maiko.costa\testeQtConsole\debug>testeQtConsole.exe
aeiou ßÚݾ·
aeiou ßÚݾ·
C:\Users\maiko.costa\testeQtConsole\debug>
I've tried it too, but with the same previous output:
#include <QCoreApplication>
#include <QDebug>
#include <QTextCodec>
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);
QTextCodec *codec = QTextCodec::codecForName("CP1252");
QTextCodec::setCodecForCStrings(codec);
qDebug() << "aeiou áéíóú";
std::cout << "aeiou áéíóú" << endl;
return 0;
}
The System encode for Windows 7 is it right ?
what am I missing ?
I am not that familiar with QT but I think this can help you just as well. The Windows console uses the OEM char set. Therefore, in order to properly print characters on std::cout they need to be encoded using OEM. This can be accomplished using the Windows API CharToOem.
Small example, just so you get the idea (here input is assumed to be UTF16):
void oemPrint(const wchar_t* str) {
char* chars = (char*)alloca(strlen(str)+1);
CharToOemW(str, chars);
fputs(chars, stdout);
}
// Usage:
oemPrint(L"aeiou áéíóú");
EDIT: A QT solution might be to use QTextCodec::codecForName("IBM 850") - this is the OEM codec.
I find the solution in this thread. Output unicode strings in Windows console app
If I ran chcp 65001 in windows console before I ran my app the characters are printed correctly.
I don't know how to workaround it in my source code, then I call this program manually with the start cpp function.
Here is the return line of function I wrote that displays passwords as ● ● ● ● ●
return QString::fromUtf8( "\u25CF \u25CF \u25CF \u25CF \u25CF" );
QString::fromUnicode should work the same.
Maybe something like:
QString x = QString::fromUtf8( "\u25CF \u25CF \u25CF \u25CF \u25CF" );
std::cout << qPrintable(x) << std::endl;
Of course change it to QString::fromUnicode... hope this helps
QString a="aeiou áéíóú";
std::cout<< a.toStdString().data();
I'm using boost::date_time in my project. When date is not valid it thorws std::out_of_range C++ exception. In Qt's gui application on windows platform it becomes SEH exception, so it doesn't catched with try|catch paradigm and programm dies. How can I catch the exception platform independently?
try{
std::string ts("9999-99-99 99:99:99.999");
ptime t(time_from_string(ts))
}
catch(...)
{
// doesn't work on windows
}
EDITED:
If somebody didn't understand, I wrote another example:
Qt pro file:
TEMPLATE = app
DESTDIR = bin
VERSION = 1.0.0
CONFIG += debug_and_release build_all
TARGET = QExceptExample
SOURCES += exceptexample.cpp \
main.cpp
HEADERS += exceptexample.h
exceptexample.h
#ifndef __EXCEPTEXAMPLE_H__
#define __EXCEPTEXAMPLE_H__
#include <QtGui/QMainWindow>
#include <QtGui/QMessageBox>
#include <QtGui/QPushButton>
#include <stdexcept>
class PushButton;
class QMessageBox;
class ExceptExample : public QMainWindow
{
Q_OBJECT
public:
ExceptExample();
~ExceptExample();
public slots:
void throwExcept();
private:
QPushButton * throwBtn;
};
#endif
exceptexample.cpp
#include "exceptexample.h"
ExceptExample::ExceptExample()
{
throwBtn = new QPushButton(this);
connect(throwBtn, SIGNAL(clicked()), this, SLOT(throwExcept()));
}
ExceptExample::~ExceptExample()
{
}
void ExceptExample::throwExcept()
{
QMessageBox::information(this, "info", "We are in throwExcept()",
QMessageBox::Ok);
try{
throw std::out_of_range("ExceptExample");
}
catch(...){
QMessageBox::information(this, "hidden", "Windows users can't see "
"this message", QMessageBox::Ok);
}
}
main.cpp
#include "exceptexample.h"
#include <QApplication>
int main(int argc, char* argv[])
{
QApplication app(argc, argv);
ExceptExample e;
e.show();
return app.exec();
}
Adding answer from the comments:
aschelper wrote:
Is your Qt library compiled with C++
exception support enabled? Sometimes
they're not, which causes problems.
hoxnox (OP) answered:
#aschelper I reconfigured Qt with
-exceptions option. It fixed situation. If you'll post the answer
I'll mark it as right.
I have a Qt GUI application running on Windows that allows command-line options to be passed and under some circumstances I want to output a message to the console and then quit, for example:
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
if (someCommandLineParam)
{
std::cout << "Hello, world!";
return 0;
}
MainWindow w;
w.show();
return a.exec();
}
However, the console messages do not appear when I run the app from a command-prompt. Does anyone know how I can get this to work?
Windows does not really support dual mode applications.
To see console output you need to create a console application
CONFIG += console
However, if you double click on the program to start the GUI mode version then you will get a console window appearing, which is probably not what you want. To prevent the console window appearing you have to create a GUI mode application in which case you get no output in the console.
One idea may be to create a second small application which is a console application and provides the output. This can call the second one to do the work.
Or you could put all the functionality in a DLL then create two versions of the .exe file which have very simple main functions which call into the DLL. One is for the GUI and one is for the console.
Add:
#ifdef _WIN32
if (AttachConsole(ATTACH_PARENT_PROCESS)) {
freopen("CONOUT$", "w", stdout);
freopen("CONOUT$", "w", stderr);
}
#endif
at the top of main(). This will enable output to the console only if the program is started in a console, and won't pop up a console window in other situations. If you want to create a console window to display messages when you run the app outside a console you can change the condition to:
if (AttachConsole(ATTACH_PARENT_PROCESS) || AllocConsole())
void Console()
{
AllocConsole();
FILE *pFileCon = NULL;
pFileCon = freopen("CONOUT$", "w", stdout);
COORD coordInfo;
coordInfo.X = 130;
coordInfo.Y = 9000;
SetConsoleScreenBufferSize(GetStdHandle(STD_OUTPUT_HANDLE), coordInfo);
SetConsoleMode(GetStdHandle(STD_OUTPUT_HANDLE),ENABLE_QUICK_EDIT_MODE| ENABLE_EXTENDED_FLAGS);
}
int main(int argc, char *argv[])
{
Console();
std::cout<<"start##";
qDebug()<<"start!";
You can't use std::cout as others have said,my way is perfect even for some code can't include "qdebug" !
So many answers to this topic. 0.0
So I tried it with Qt5.x from Win7 to Win10. It took me some hours to have a good working solution which doesn't produce any problems somewhere in the chain:
#include "mainwindow.h"
#include <QApplication>
#include <windows.h>
#include <stdio.h>
#include <iostream>
//
// Add to project file:
// CONFIG += console
//
int main( int argc, char *argv[] )
{
if( argc < 2 )
{
#if defined( Q_OS_WIN )
::ShowWindow( ::GetConsoleWindow(), SW_HIDE ); //hide console window
#endif
QApplication a( argc, argv );
MainWindow *w = new MainWindow;
w->show();
int e = a.exec();
delete w; //needed to execute deconstructor
exit( e ); //needed to exit the hidden console
return e;
}
else
{
QCoreApplication a( argc, argv );
std::string g;
std::cout << "Enter name: ";
std::cin >> g;
std::cout << "Name is: " << g << std::endl;
exit( 0 );
return a.exec();
}
}
I tried it also without the "CONFIG += console", but then you need to redirect the streams and create the console on your own:
#ifdef _WIN32
if (AttachConsole(ATTACH_PARENT_PROCESS) || AllocConsole()){
freopen("CONOUT$", "w", stdout);
freopen("CONOUT$", "w", stderr);
freopen("CONIN$", "r", stdin);
}
#endif
BUT this only works if you start it through a debugger, otherwise all inputs are directed towards the system too. Means, if you type a name via std::cin the system tries to execute the name as a command. (very strange)
Two other warnings to this attempt would be, that you can't use ::FreeConsole() it won't close it and if you start it through a console the app won't close.
Last there is a Qt help section in QApplication to this topic. I tried the example there with an application and it doesn't work for the GUI, it stucked somewhere in an endless loop and the GUI won't be rendered or it simply crashes:
QCoreApplication* createApplication(int &argc, char *argv[])
{
for (int i = 1; i < argc; ++i)
if (!qstrcmp(argv[i], "-no-gui"))
return new QCoreApplication(argc, argv);
return new QApplication(argc, argv);
}
int main(int argc, char* argv[])
{
QScopedPointer<QCoreApplication> app(createApplication(argc, argv));
if (qobject_cast<QApplication *>(app.data())) {
// start GUI version...
} else {
// start non-GUI version...
}
return app->exec();
}
So if you are using Windows and Qt simply use the console option, hide the console if you need the GUI and close it via exit.
No way to output a message to console when using QT += gui.
fprintf(stderr, ...) also can't print output.
Use QMessageBox instead to show the message.
Oh you can Output a message when using QT += gui and CONFIG += console.
You need printf("foo bar") but cout << "foo bar" doesn't works
Something you may want to investigate, at least for windows, is the AllocConsole() function in the windows api. It calls GetStdHandle a few times to redirect stdout, stderr, etc. (A quick test shows this doesn't entirely do what we want it to do. You do get a console window opened alongside your other Qt stuff, but you can't output to it. Presumably, because the console window is open, there is some way to access it, get a handle to it, or access and manipulate it somehow. Here's the MSDN documentation for those interested in figuring this out:
AllocConsole():
http://msdn.microsoft.com/en-us/library/windows/desktop/ms681944%28v=vs.85%29.aspx
GetStdHandle(...):
http://msdn.microsoft.com/en-us/library/windows/desktop/ms683231%28v=vs.85%29.aspx
(I'd add this as a comment, but the rules prevent me from doing so...)
I used this header below for my projects. Hope it helps.
#ifndef __DEBUG__H
#define __DEBUG__H
#include <QtGui>
static void myMessageOutput(bool debug, QtMsgType type, const QString & msg) {
if (!debug) return;
QDateTime dateTime = QDateTime::currentDateTime();
QString dateString = dateTime.toString("yyyy.MM.dd hh:mm:ss:zzz");
switch (type) {
case QtDebugMsg:
fprintf(stderr, "Debug: %s\n", msg.toAscii().data());
break;
case QtWarningMsg:
fprintf(stderr, "Warning: %s\n", msg.toAscii().data());
break;
case QtCriticalMsg:
fprintf(stderr, "Critical: %s\n", msg.toAscii().data());
break;
case QtFatalMsg:
fprintf(stderr, "Fatal: %s\n", msg.toAscii().data());
abort();
}
}
#endif
PS: you could add dateString to output if you want in future.
First of all, why would you need to output to console in a release mode build? Nobody will think to look there when there's a gui...
Second, qDebug is fancy :)
Third, you can try adding console to your .pro's CONFIG, it might work.
In your .pro add
CONFIG += console
It may have been an oversight of other answers, or perhaps it is a requirement of the user to indeed need console output, but the obvious answer to me is to create a secondary window that can be shown or hidden (with a checkbox or button) that shows all messages by appending lines of text to a text box widget and use that as a console?
The benefits of such a solution are:
A simple solution (providing all it displays is a simple log).
The ability to dock the 'console' widget onto the main application window. (In Qt, anyhow).
The ability to create many consoles (if more than 1 thread, etc).
A pretty easy change from local console output to sending log over network to a client.
Hope this gives you food for thought, although I am not in any way yet qualified to postulate on how you should do this, I can imagine it is something very achievable by any one of us with a little searching / reading!
Make sure Qt5Core.dll is in the same directory with your application executable.
I had a similar issue in Qt5 with a console application:
if I start the application from Qt Creator, the output text is visible,
if I open cmd.exe and start the same application there, no output is visible.
Very strange!
I solved it by copying Qt5Core.dll to the directory with the application executable.
Here is my tiny console application:
#include <QCoreApplication>
#include <QDebug>
int main(int argc, char *argv[])
{
int x=343;
QString str("Hello World");
qDebug()<< str << x<<"lalalaa";
QTextStream out(stdout);
out << "aldfjals alsdfajs...";
}
I also played with this, discovering that redirecting output worked, but I never saw output to the console window, which is present for every windows application. This is my solution so far, until I find a Qt replacement for ShowWindow and GetConsoleWindow.
Run this from a command prompt without parameters - get the window. Run from command prompt with parameters (eg. cmd aaa bbb ccc) - you get the text output on the command prompt window - just as you would expect for any Windows console app.
Please excuse the lame example - it represents about 30 minutes of tinkering.
#include "mainwindow.h"
#include <QTextStream>
#include <QCoreApplication>
#include <QApplication>
#include <QWidget>
#include <windows.h>
QT_USE_NAMESPACE
int main(int argc, char *argv[])
{
if (argc > 1) {
// User has specified command-line arguments
QCoreApplication a(argc, argv);
QTextStream out(stdout);
int i;
ShowWindow (GetConsoleWindow(),SW_NORMAL);
for (i=1; i<argc; i++)
out << i << ':' << argv [i] << endl;
out << endl << "Hello, World" << endl;
out << "Application Directory Path:" << a.applicationDirPath() << endl;
out << "Application File Path:" << a.applicationFilePath() << endl;
MessageBox (0,(LPCWSTR)"Continue?",(LPCWSTR)"Silly Question",MB_YESNO);
return 0;
} else {
QApplication a(argc, argv);
MainWindow w;
w.setWindowTitle("Simple example");
w.show();
return a.exec();
}
}
After a rather long struggle with exactly the same problem I found that simply
CONFIG += console
really does the trick. It won't work until you explicitly tell QtCreator to execute qmake on the project (right click on project) AND change something inside the source file, then rebuild. Otherwise compilation is skipped and you still won't see the output on the command line.
Now my program works in both GUI and cmd line mode.
One solution is to run powershell and redirect the output to whatever stream you want.
Below is an example of running powershell from cmd.exe and redirecting my_exec.exe output to both the console and an output.txt file:
powershell ".\my_exec.exe | tee output.txt"
An example (from cmd.exe) which holds open stdout/stderr and doesn't require tee or a temporary file:
my_exec.exe > NUL 2>&1
Easy
Step1: Create new project. Go File->New File or Project --> Other Project -->Empty Project
Step2: Use the below code.
In .pro file
QT +=widgets
CONFIG += console
TARGET = minimal
SOURCES += \ main.cpp
Step3: Create main.cpp and copy the below code.
#include <QApplication>
#include <QtCore>
using namespace std;
QTextStream in(stdin);
QTextStream out(stdout);
int main(int argc, char *argv[]){
QApplication app(argc,argv);
qDebug() << "Please enter some text over here: " << endl;
out.flush();
QString input;
input = in.readLine();
out << "The input is " << input << endl;
return app.exec();
}
I created necessary objects in the code for your understanding.
Just Run It
If you want your program to get multiple inputs with some conditions. Then past the below code in Main.cpp
#include <QApplication>
#include <QtCore>
using namespace std;
QTextStream in(stdin);
QTextStream out(stdout);
int main(int argc, char *argv[]){
QApplication app(argc,argv);
qDebug() << "Please enter some text over here: " << endl;
out.flush();
QString input;
do{
input = in.readLine();
if(input.size()==6){
out << "The input is " << input << endl;
}
else
{
qDebug("Not the exact input man");
}
}while(!input.size()==0);
qDebug(" WE ARE AT THE END");
// endif
return app.exec();
} // end main
Hope it educates you.
Good day,
First of all you can try flushing the buffer
std::cout << "Hello, world!"<<std::endl;
For more Qt based logging you can try using qDebug.