So, I've written a C executable on Linux for Windows using mingw32-gcc. It is a basic Input-Output program, you type an input and get an answer.
Problem is the cmd shuts down immediately, so the user can't see the output.
Assuming I cannot use Windows to edit the executable there, what should I change in my code/ what flags should I use when compiling it?
inb4:
the user is supposed to click and run it, so running it from cmd won't help.
adding getchar()/scanf() at the end of my code doesn't work, and it feels a bit like cheating.
SOLVED: so all I had to do was to actually add a getchar() after every scanf() and one more at the end of the code for the user input to close the cmd.
Waiting for input at the end is not cheating, but common practice. How else should program know for how long it should stay opened? Closing program by closing console window directly is more cheating than waiting for user input to finish.
You can for example prompt user to hit any key like Press any key to exit... or something similar.
If you want some specific delay, you can use Sleep() from windows.h instead of waiting for input.
See https://stackoverflow.com/a/3379146/3035795
I'd like to do something similar to Removing PDF password protection, knowing the password but in Windows. I have a folder with several PDFs that all have the same password, which I know. I would like to remove the password and overwrite the original files (don't worry, my data is a copy of another folder).
My thoughts are to use Autohotkey and create a script to open the file, paste the password, click enter, press Ctrl+P, click Print as PDF, save as the original file name, close Edge (which is what I'm using to open the PDFs), and then go to the next file in the folder.
I'm honestly not that familiar with AHK and would appreciate any help in what the code should be.
Thanks!
Edit: Here's some code I've tried but it doesn't seem to work.
^+q::
Loop %A_WorkingDir%\*.pdf
sleep 10000
Send, PASSWORD
sleep 2000
Send, {Enter}
Send, ^p
Click 105,694
WinClose, A
Return
When looping through files (using a files-loop as you have), it's not actually opening these but is giving you access to its OS-level properties, such as path, name, and system properties. You can use this information to open each one, using Run - something like, Run , %A_LoopFileLongPath%. Note that you may need to set Edge as your default PDF viewer if it isn't already.
Currently, your loop is only executing the line just beneath it, which is a 10-sec. sleep. You have 2,000 PDFs? That's about 5.5 hours of sleep before moving on. ;) If you want to execute more than one line, enclose it in braces { }, like so:
Loop , 1000
{
; stuff
}
From there, I would consider using WinWaitActive along with possibly ControlSend instead of Sleep and possibly Send. This will make your script more robust and may also take less time (assuming 10s is an upper bound). If at all possible, I would also discourage using clicks as these can sometimes be problematic (sometimes you have to send it multiple times for one click or locations might change). You can definitely make it work without these suggestions, it just might take more trial-and-error.
It may also be a good idea to build in a way to pause your script if needed, since this will likely take some time to do things to 2,000 files.
The help documentation is excellent and shows proper syntax and examples. I'd recommend consulting it for each of the commands.
https://www.autohotkey.com/docs/AutoHotkey.htm
I have a problem with a project in Visual Studio. The project is created as an empty project, and then a .c file was added. The problem is that the console closes immediately after the program ends when I redirect input to a file.
I tried going to Properties > Linker > System and selecting /SUBSYSTEM:CONSOLE option, but it doesn't solve this. This always worked for me, but now when I redirected the input, the console closes right after the program execution and I can't see the output.
I redirected the output by adding <"in.txt" in Configuration properties > Debugger > Command, and it works exactly the way I wanted, except the console closes too soon. This problem doesn't occur when I redirect the output.
Also using getchar(), scanf(...) or system("pause") didn't work.
I would love to solve this by only changing some project settings and without adding some extra code to a program if possible, but any solution is appreciated.
Edit: As I stated above, I have tried several things, including some answers from similar questions, but none of them helped.
It's standard windows behavior that a console program automatically gets a new console window when not started from an existing one and this new window is automatically closed as soon as the program ends. So the key to force the window to stay open from withing your program is to prevent program termination.
With things like getchar(), you rely on the fact that these calls block until more input is available. This works fine as long as input actually comes from the console. But when you redirect input to come from a file, there will always be input available -- either there's more to read from the file or you'll instantly get an error (e.g. for EOF). That's the reason all these "tricks" don't work any more.
A simple and very unclean version is to just add an empty loop to the end of your program, so it never exits. On the windows platform, this could be something like
for (;;) Sleep(1000);
The call to Sleep() (include windows.h to use it) makes sure this loop doesn't burn CPU cycles. You'll have to forcefully end your program by hitting Ctrl+C or closing the window. Of course, don't leave this loop in your final program, it would be quite annoying when started from an existing console window.
There might be better solutions to this problem, but I hope I could explain you why this is happening.
I think this is simple, but not for me obviously!
I have a console-application. I need to read input from the keyboard, but stdin has been redirected to a file. So how do I create a FILE-Handle that points at the keyboard-stream which i can use with fgets etc.?
I found out that ttyname(0) seems to be what i look for in a POSIX-environment, which I don't have here. I'm in a Windows-system with standard Visual Studio compiler.
Any ideas? Thank you in advance.
There's no easy/portable way to tell if a keyboard exists (your application may be being run from a terminal emulator from a serial port, a telnet session or anything else). If a keyboard actually does exist (including a picture of a keyboard on a touch screen), then you can't really tell how many layers of software the keystrokes need to pass through before they get to your application (e.g. keystrokes might go from a keyboard driver to an input method editor to a GUI to a shell to your application). This means that attempting to get keystrokes directly from a keyboard driver or something is a bad idea that will fail in almost all cases.
The best way to solve your problem is to find out which series of design failures led to STDIN being redirected in the first place.
For example; maybe the application should've had a command line option to read some data from a file; so that the application can get some data from the file and some from STDIN (and get all data from STDIN if the command line option isn't present).
Pulling from the dim dark days of DOS programming here: try opening "CON:" (Console), a reserved word. Hopefully it will open the same way in Windows. The colon may or may not be required. Both "dir >con:" and "dir >con" still work in command prompt.
Also, be sure to use something from the setbuf() family on the output handle to avoid buffering... it's not supposed to buffer terminal I/O, but it never hurts to be sure.
Again, not sure, but I suspect opening separate FILE *conin, *conout for output and one for input may help if you seem to have troubles with one handle doing both input and output.
I'm trying to build an .exe file for the K&R "Hello, world". The code given in the book is:
#include <stdio.h>
main()
{
printf("Hello, world!\n");
}
When I build & run from Code::Blocks (under Windows XP), I get the prompt window with the "hello world" message. It stays open until I close it manually. However, when I double click the .exe file, the prompt just flashes and disappears, why is that?
No one is explicitly telling you this, so I will:
What you see when you double-click the file is normal. What your IDE does (keeping the window open) is a feature to help you debug the application.
Why is this so?
Since you're developing a console application, there has to be a console for your application to display its output on. If there is none yet, a new console is created (which is the black window).
If you launch your program from inside a console (say, from cmd.exe), it will just inherit the console of the parent without creating a new one[1].
After the last application using the console exits (which, in the first case is just your program), the console closes. You will notice this all the time for console applications that print nothing but a help text when run without parameters. If you double-click them from explorer, a black window with some text will flash and then immediately close.
Sometimes, a program that does something and them immediately closes is what you want. For example, you can call these applications from scripts.
On the other hand, your application could be interactive: waiting for user input, doing some thing, and only exiting when the user tells it to. You cannot script these applications, obviously, as you will need to have a human present at the keyboard to tell the application what to do.
Now we get to the IDE part: let's say you're developing an application of the first kind, one that does something and then immediately closes. It's not very convenient to have the screen flash and disappear every time you run it, because how can you tell if the program worked? Assuming you can tell this from the output it generates.
You could of course start a command-line window and run the application from there, but the program would execute separately from the IDE, and you would lose live debugging capabilities.
So, IDE makers came up with a feature for console applications: when you run the application directly from your IDE, they afterwards, usually waiting for a keypress. This gives you the opportunity to inspect the window with the output, to confirm that the application is working properly.
[1] Esoterica: unless you go through an application that does not inherit the console. Any console app launched by that application will not inherit the console, since the inheritance was broken by the GUI app. For example, start.exe does this. Compare:
foo.exe (inherits the console)
start foo.exe (start.exe is a GUI app, so foo.exe is launched in a new console)
If you're not running a command line exe from an already open command line window, Windows will automatically close the windows after the program has terminated. Try opening cmd.exe, navigating to your program's directory and running it from there, the window should stay open.
When running from IDE's like this, they run the program and when its done running, they close it.
Since your program's only function is to print out a value, it does that and closes.
You should try to add something that asks for user input at the end or compile it into an .exe and run itself from the command line yourself.
Since you are starting I would recommend to just run it from the command line yourself. You will eventually learn about user input and there you can have the command line window open when you use your program.
Normal behavior.
Your program executes every action in the order of the main. So it prints, and then moves on to the next operation, there is none, so it exits. Since the console window is tied to your .exe, the command window closes with the program.
If you don't want your program to exit right away, you can make it sleep, or wait for user input before exiting.
When double clicking a .exe in Windows, you are launching a new process. Windows has 2 basic process types: Window and Command line. The hello world sample you've written is a command line process.
A command line process will launch a new command window on startup. This is the window that pops up which is largely a black background with white text. Upon completion of a program the window will close down.
Add getch(); before the closing brace. This will prompt for an input after the output is printed. Once you key in a character the window will close. This should solve your problem.
The preferred solution is to run the executable from the command line.
Try running your binary from the command line.
That is because the executable file opens its own dialog box. When the executable has completed running it shuts down the dialog box that it opened in order to run. However, when YOU are the one that opened the dialog box, it disappears when YOU close it.
So if you were to open up a command prompt and then run the executable, the dialog box would not automatically close.
That is because from the executable, it executes your code in a new window and then the process is done, it has no reason to stay open, what you wanted to do is complete. There are a couple of things you can do. You can execute it from the cmd.exe command line, or you could even put something at the end of your code that listens for a key press, and once the key stroke is detected, allow the program to exit.
just add
system("pause");
line before return. it`s not the best, but universal method.
Here is my take on this:
// Hello sweetie (Spoilers)
#include <iostream>
using namespace std;
int main()
{
// Print the text to screen
cout << "************************************";
cout << "\n";
cout << "Hello World!";
cout << "\n";
cout << "You may close me by pressing Enter";
cout << "\n";
cout << "************************************";
cout << "\n";
cout << "\n";
/*
This will prompt for an input after the output is printed.
Once you hit the Enter key the window will close.
*/
if (cin.get() == '\n')
return 0;
}