I am writing a simple OpenGL program with Qt Creator which basically creates a QGLWidget, shows it, and runs the application loop. I usually like debugging more with diagnostic messages turned on and off by preprocessor symbols that using an actual debugger and watches etc. In Qt Creator we have a tab called Application Output, but all I see there is "Starting xxx.exe. xxx.exe exited with code 0". No output from either std::cout or std::cerr. Now I know I could start my application from cmd.exe (yes, I am using Windows, love it :P) and see the output there but I wish I could see the output directly from the IDE. Is that possible? Thanks
Usually the Application Output pane works fine. Are you sure that you would see the output from cmd.exe (have you actually tried?)? It's usually turned off for UI applications to avoid console windows from popping up. Try CONFIG += console. Also check if you see qDebug() messages in the Application Output.
simply #include <QDebug>
and then use qDebug instead of cout like
qDebug() << "you just clicked ok";
also this works
#include <QTextStream>
QTextStream out(stdout);
out << "\nHello World!\n";
adding CONFIG += console in the .pro file didn't work for me. I wonder why?
i just discovered that i've to add "endl;" for cout to work like
cout << "print this" << endl;
Alternatively, you can check the "run in console" setting in the Project->Run options. This will open a new console window and display all console output there (if CONFIG += console is used of course).
I know that this answer do not answer the original question, but since when searching for "No application output" we found this answer...
See the following answer: https://stackoverflow.com/a/26325743/808101
This only apply to qDebug() and similar functions (not direct output to stdout/stderr).
In my case, I have to set QT_ASSUME_STDERR_HAS_CONSOLE environment variable to 1 in QtCreator in order to see qDebug() messages inside "Application Output" window.
Try:
Tools -> Options
Under the "General" tab of "Environment" change the terminal entry from:
x-terminal-emulator -e
to
xterm -e
Related
If I run the code::blocks default console c++ "hello world" app (see below), I only see this in the console that opens :
Process returned 0 (0x0) execution time : 0.011 s
Press any key to continue.
I don't see "hello world". What could be wrong ?
If I run the ./helloworld.exe with cygwin, I do see "hello world". But I don't see it with cmd or powershell.
The app :
#include <iostream>
using namespace std;
int main()
{
cout << "Hello world!" << endl;
return 0;
}
There is a related discussion you might want to check out here:
http://www.tomsguide.com/forum/244674-49-basic-program
It could be a matter of the program executing too quickly, per the forum I referenced above, but that seems like an odd reason. You might try what they recommend (pause, etc.), but you may also have an issue with your compiler or how your properties are set up.
For cmd, check this out:
https://www.thecrazyprogrammer.com/2015/09/how-to-run-c-and-cpp-program-in-cmd.html
For the command line/Windows prompt, check this out:
https://msdn.microsoft.com/en-us/library/ms235639.aspx
Thanks to #George.
Solution was to remove the -mwindows compiler flag.
But to make it work, I needed to delete the .exe before building again.
This is a probably an embarasing question as no doubt the answer is blindingly obvious.
I've used Visual Studio for years, but this is the first time I've done any 'Console Application' development.
When I run my application the console window pops up, the program output appears and then the window closes as the application exits.
Is there a way to either keep it open until I have checked the output, or view the results after the window has closed?
If you run without debugging (Ctrl+F5) then by default it prompts your to press return to close the window. If you want to use the debugger, you should put a breakpoint on the last line.
Right click on your project
Properties > Configuration Properties > Linker > System
Select Console (/SUBSYSTEM:CONSOLE) in SubSystem option or you can just type Console in the text field!
Now try it...it should work
Starting from Visual Studio 2017 (15.9.4) there is an option:
Tools->Options->Debugging->Automatically close the console
The corresponding fragment from the Visual Studio documentation:
Automatically close the console when debugging stops:
Tells Visual Studio to close the console at the end of a debugging session.
Here is a way for C/C++:
#include <stdlib.h>
#ifdef _WIN32
#define WINPAUSE system("pause")
#endif
Put this at the top of your program, and IF it is on a Windows system (#ifdef _WIN32), then it will create a macro called WINPAUSE. Whenever you want your program to pause, call WINPAUSE; and it will pause the program, using the DOS command. For other systems like Unix/Linux, the console should not quit on program exit anyway.
Goto Debug Menu->Press StartWithoutDebugging
If you're using .NET, put Console.ReadLine() before the end of the program.
It will wait for <ENTER>.
try to call getchar() right before main() returns.
(/SUBSYSTEM:CONSOLE) did not worked for my vs2013 (I already had it).
"run without debugging" is not an options, since I do not want to switch between debugging and seeing output.
I ended with
int main() {
...
#if _DEBUG
LOG_INFO("end, press key to close");
getchar();
#endif // _DEBUG
return 0;
}
Solution used in qtcreator pre 2.6. Now while qt is growing, vs is going other way. As I remember, in vs2008 we did not need such tricks.
just put as your last line of code:
system("pause");
Here's a solution that (1) doesn't require any code changes or breakpoints, and (2) pauses after program termination so that you can see everything that was printed. It will pause after either F5 or Ctrl+F5. The major downside is that on VS2013 Express (as tested), it doesn't load symbols, so debugging is very restricted.
Create a batch file. I called mine runthenpause.bat, with the following contents:
%1 %2 %3 %4 %5 %6 %7 %8 %9
pause
The first line will run whatever command you provide and up to eight arguments. The second line will... pause.
Open the project properties | Configuration properties | Debugging.
Change "Command Arguments" to $(TargetPath) (or whatever is in "Command").
Change "Command" to the full path to runthenpause.bat.
Hit OK.
Now, when you run, runthenpause.bat will launch your application, and after your application has terminated, will pause for you to see the console output.
I will post an update if I figure out how to get the symbols loaded. I tried /Z7 per this but without success.
add “| pause” in command arguments box under debugging section at project properties.
You could run your executable from a command prompt. This way you could see all the output. Or, you could do something like this:
int a = 0;
scanf("%d",&a);
return YOUR_MAIN_CODE;
and this way the window would not close until you enter data for the a variable.
Just press CNTRL + F5 to open it in an external command line window (Visual Studio does not have control over it).
If this doesn't work then add the following to the end of your code:
Console.WriteLine("Press any key to exit...");
Console.ReadKey();
This wait for you to press a key to close the terminal window once the code has reached the end.
If you want to do this in multiple places, put the above code in a method (e.g. private void Pause()) and call Pause() whenever a program reaches a possible end.
A somewhat better solution:
atexit([] { system("PAUSE"); });
at the beginning of your program.
Pros:
can use std::exit()
can have multiple returns from main
you can run your program under the debugger
IDE independent (+ OS independent if you use the cin.sync(); cin.ignore(); trick instead of system("pause");)
Cons:
have to modify code
won't pause on std::terminate()
will still happen in your program outside of the IDE/debugger session; you can prevent this under Windows using:
extern "C" int __stdcall IsDebuggerPresent(void);
int main(int argc, char** argv) {
if (IsDebuggerPresent())
atexit([] {system("PAUSE"); });
...
}
Either use:
cin.get();
or
system("pause");
Make sure to make either of them at the end of main() function and before the return statement.
You can also use this option
#include <conio.h>
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int main() {
.
.
.
getch();
return 0;
}
In my case, i experienced this when i created an Empty C++ project on VS 2017 community edition. You will need to set the Subsystem to "Console (/SUBSYSTEM:CONSOLE)" under Configuration Properties.
Go to "View" then select "Property Manager"
Right click on the project/solution and select "Property". This opens a Test property page
Navigate to the linker then select "System"
Click on "SubSystem" and a drop down appears
Choose "Console (/SUBSYSTEM:CONSOLE)"
Apply and save
The next time you run your code with "CTRL +F5", you should see the output.
Sometimes a simple hack that doesnt alter your setup or code can be:
Set a breakpoint with F9, then execute Debug with F5.
Since running it from VS attaches the VS debugger, you can check for an attached debugger:
if (Debugger.IsAttached)
{
Console.WriteLine("Debugger is attached. Press any key to exit.");
Console.ReadKey();
}
I guess the only caveat is that it'll still pause if you attach any other debugger, but that may even be a wanted behavior.
Use Console.ReadLine() at the end of the program. This will keep the window open until you press the Enter key. See https://learn.microsoft.com/en-us/dotnet/api/system.console.readline for details.
Visual Studio 2015, with imports. Because I hate
when code examples don't give the needed imports.
#include <iostream>;
int main()
{
getchar();
return 0;
}
Currently there is no way to do this with apps running in WSL2. However there are two work-arounds:
The debug window retains the contents of the WSL shell window that closed.
The window remains open if your application returns a non-zero return code, so you could return non-zero in debug builds for example.
It should be added that things have changed since then. On Windows 11 (probably 10, I can't check any more) the new Terminal app that now houses the various console, PowerShell and other sessions has its own settings regarding closing. Look for it in Settings > Defaults > Advanced > Profile termination behavior.
If it's set to close when a program exits with zero, then it will close, even if VS is told otherwise.
Go to Setting>Debug>Un-check close on end.
Shouldn't this work? I mean, the code is merely a test and is meant so that the dialogue goes this way : What is your name? name here, Hello name here, and yet it does not show the last line of Hello after I type in my name and click enter it just dissapears. Here is the code.
#include <iostream>
#include <string>
int main (void)
{
using std::cin;
using std::cout;
using std::string;
string name = "";
cout << "What is your name, pls?\n";
cin >> name;
cout << "\nHello " << name.c_str() << "\n";
return 0;
}
My guess is that you are running from the debugger, or double clicking the executable. In either of those cases, when the program ends, the console will close. So, the program produced output, but you just could not see it before the console closed.
Run the program from a pre-existing console so that the console remains after your program ends. Or, just whilst debugging, arrange that your program does not terminate immediately after emitting its final output. A simple way to do that is to place a break point at the end of the program.
It probably showed it right before it disappeared. If you're going to write console programs, and if you're going to send output to a console, you should run them from a console so the output has some place to go.
After you are done with your program, press Ctrl + F5 ( Run without debugging). This will prompt before closing the window and this is what you want.
Make sure you put a breakpoint before main goes out of scope. I guess your console disappears under VS?
Also, you don't need to extract the char* in the last cout statement:
cout << "\nHello " << name << endl;
Open a terminal (or a command prompt window).
Navigate to the folder that contains the executable.
Run it.
It's not disappearing. It is just running really fast.
Every IDE has a keyboard shortcut that allows you to run code and pause after the execution has finished.
This keyboard shortcut is Ctrl-F5 in Visual Studio.
I have no idea what IDE you're running, but that is your basic problem.
The other thing you can do is to test your code in ideone : ideone.com/hb4Cel (it's the same code. There is no point pasting it here)
A dirty workaround is to add something like this
cin >> name;
at the end, just before return 0;. It forces the window to wait for input (i.e. hitting return) before returning (which closes the program).
This isn't necessarily good design, but if all you want to do is run some tests then it'll do the trick.
Basically when you enter your name it displays your last line and exits after return 0.
Here are the following things to avoid that
1- use command line to run the application
Start->accessories->command prompt
Go to folder in which your application is using cd command
c:>cd c:\path\foldername
Now run the application by typing the program name e.g
c:\path\foldername>my_application.exe
It will display your last line.
2- Now if your are using microsoft visual c++ press ctrl+F5 to run your program
3- This is not recommended but you an use it as long as your are debugging then remove it from the code afterwards. Include conio.h header file and add getch(); line before return statement. It would hold the screen for you till you press a key.
When I run console applications in QtCreator the output (and input - std::cout, std::cin) is done via xterm (my OS is debian). How can I make output to be shown in the QtCreator's output pane not in the xterm window?
From the Qt Creator website:
Application Output
The Application Output pane displays the status of a program when it is executed, and the debug output.
http://doc.qt.digia.com/qtcreator/creator-quick-tour.html
It does not look like the Application Output window is what you think it is.
You should use the QDebug() function for this. It's usage is pretty much the same as std::cout.
Look at the example below:
float coordinate = 3.41;
qDebug() << "Custom coordinate type:" << coordinate;
This will output, in your QtCreator's output pane:
Custom coordinate type: 3.41
Don't forget to include this statement, in your includes block:
#include <QDebug>
For more information, check this link: http://doc.qt.io/qt-5/qdebug.html
When using iostream in C++ on Linux, it displays the program output in the terminal, but in Windows, it just saves the output to a stdout.txt file. How can I, in Windows, make the output appear in the console?
Since you mentioned stdout.txt I google'd it to see what exactly would create a stdout.txt; normally, even with a Windows app, console output goes to the allocated console, or nowhere if one is not allocated.
So, assuming you are using SDL (which is the only thing that brought up stdout.txt), you should follow the advice here. Either freopen stdout and stderr with "CON", or do the other linker/compile workarounds there.
In case the link gets broken again, here is exactly what was referenced from libSDL:
How do I avoid creating stdout.txt and stderr.txt?
"I believe inside the Visual C++ project that comes with SDL there is a SDL_nostdio target > you can build which does what you want(TM)."
"If you define "NO_STDIO_REDIRECT" and recompile SDL, I think it will fix the problem." > > (Answer courtesy of Bill Kendrick)
For debugging in Visual Studio you can print to the debug console:
OutputDebugStringW(L"My output string.");
If you have a none-console Windows application, you can create a console with the AllocConsole function. Once created, you can write to it using the normal std::cout methods.
If you're using Visual Studio you need to modify the project property:
Configuration Properties -> Linker -> System -> SubSystem.
This should be set to: Console (/SUBSYSTEM:CONSOLE)
Also you should change your WinMain to be this signature:
int main(int argc, char **argv)
{
//...
return 0;
}
The AllocConsole Windows API function will create a console window for your application.
If you're using Visual Studio, it should work just fine!
Here's a code example:
#include <iostream>
using namespace std;
int main (int) {
cout << "This will print to the console!" << endl;
}
Make sure you chose a Win32 console application when creating a new project. Still you can redirect the output of your project to a file by using the console switch (>>). This will actually redirect the console pipe away from the stdout to your file. (for example, myprog.exe >> myfile.txt).
I wish I'm not mistaken!
Whether to use subsystem:console or subsystem:windows kind of depends on whether how you want to start your application:
If you use subsystem:console, then you get all of the stdout written to the terminal. The trouble is that if you start the application from the Start Menu/Desktop, you (by default) get a console appearing as well as the application window (which can look pretty ugly).
If you use subsystem:windows, you won't get stdout/stderr even if you run the application from a DOS window, Cygwin, or other terminal.
If you want the middle way which is to output to the terminal IF the application was started in a terminal, then follow the link that Luke provided in his solution (http://dslweb.nwnexus.com/~ast/dload/guicon.htm)
For reference, I ran into this problem with an application that I want to run in either normal Windows mode or batch mode (that is, as part of a script) depending on command-line switches. The whole differentiation between console and Windows applications is a bit bizarre to Unix folks!
First off, what compiler or dev environment are you using? If Visual Studio, you need to make a console application project to get console output.
Second,
std::cout << "Hello World" << std::endl;
should work in any C++ console application.
Your application must be compiled as a Windows console application.
There is a good solution
if (AllocConsole() == 0)
{
// Handle error here. Use ::GetLastError() to get the error.
}
// Redirect CRT standard input, output and error handles to the console window.
FILE * pNewStdout = nullptr;
FILE * pNewStderr = nullptr;
FILE * pNewStdin = nullptr;
::freopen_s(&pNewStdout, "CONOUT$", "w", stdout);
::freopen_s(&pNewStderr, "CONOUT$", "w", stderr);
::freopen_s(&pNewStdin, "CONIN$", "r", stdin);
// Clear the error state for all of the C++ standard streams. Attempting to accessing the streams before they refer
// to a valid target causes the stream to enter an error state. Clearing the error state will fix this problem,
// which seems to occur in newer version of Visual Studio even when the console has not been read from or written
// to yet.
std::cout.clear();
std::cerr.clear();
std::cin.clear();
std::wcout.clear();
std::wcerr.clear();
std::wcin.clear();
I assume you're using some version of Visual Studio? In windows, std::cout << "something"; should write something to a console window IF your program is setup in the project settings as a console program.
If using MinGW, add an option, -Wl,subsystem,console or -mconsole.
You don't necessarily need to make any changes to your code (nor to change the SUBSYSTEM type). If you wish, you also could simply pipe stdout and stderr to a console application (a Windows version of cat works well).