I have two loggers in my program. One that I made inside a gui, and one that is super complicated but very well designed and prints to the console. I am trying to get the output from the nice console logger to the rendered one. I have tried everything under the sun to get this to work but I can't seem to figure it out (due to my lack of understanding of the code from the other logger(spdlog).) My conclusion is that taking the logs directly from what is printed is the best way to do this but I can't find online anyone asking how to do this. I have seen a few questions but they just post code as an answer and don't really explain what is going on. My question: Is there a way to grab printed statements from the console and what are the performance issues/complications that come with doing something like this.
For example, if i do std::cout << "hello!" << std::endl; or some printf statement, I want to be able to further down in the code be able to grab "hello!"
My conclusion is that taking the logs directly from what is printed is the best way to do this but I can't find online anyone asking how to do this.
Consoles nowadays are terminal emulators. The original terminals' output went to printers and couldn't be (easily) read back.
Application's stdout and stderr (console) streams are write-only. Moreover, in Windows and Unix/Linux you can pipe your program's (console) output (either or both stderr and stdout) into another application with | (pipe) that creates a pipe IPC between stdout of your application and stdin of another one. That IPC pipe is write-only, your application cannot possibly read back from it.
You may be able to get access to the contents of the frame buffer of Windows cmd.exe that controls its Windows console window, but that won't be the verbatim byte-exact copy of data you wrote into stdout because of the escape sequences interpreted by Windows console.
If stdout is redirected into a file you can re-open that file for reading, but there is no portable way to re-open that file.
In other words, there is no portable way to read console output back.
I have tried everything under the sun to get this to work but I can't seem to figure it out (due to my lack of understanding of the code from the other logger(spdlog).
I bet you haven't tried reading spdlog documentation, in particular logger with multi sinks. A sink is an output abstraction, which implementation can write into a file, memory or both. What you need is attach your own sink to spdlog that prints into your UI.
Derive your sink from base_sink and implement abstract member functions:
virtual void sink_it_(const details::log_msg &msg) = 0; to print into the UI, and,
virtual void flush_() = 0; to do nothing.
Then attach one object of your sink class to that spdlog.
Related
I am new to programming and seem to be having trouble figuring out how to direct output to a printer.
cout directs to monitor, is there a command to direct to the print queue?
I have a simple console program and am using code blocks for my ide.
A problem like this is dependent on your operating system. Assuming you use windows, you may need to look at the 'Windows API' which may or may not have a method of doing this. Alternatively, you can output to a text file, then use a script to open the file, run through the print menu, and close the file which is less eloquent but will work.
I have a C++ console application that prints some output constantly while it also accepts commands (using std::cin) from the user - output and input happen in separate threads.
If I write a text while some output appears the written text is mixed with application output. How can I prevent this behaviour?
To solve this problem, I need to display the program one line above the line where the text is typed. I'd inspire myself in Minecraft Bukkit server's solution - however I need the same for C++.
Assuming you want the output to appear while things are being typed, you'll need some screen control facilities to have the output go somewhere different than the input area. If I were tasked to implement something like this writing to a terminal I would refresh my ncurses experience. I realize you are on a Windows console and I have no idea if the Windows console is capable of the screen control needed to make it happen.
You can possibly tie custom stream buffers into std::cin and std::cout using the curses functionality under the hood but it may not be worth it. In any case, it isn't entirely trivial.
There's a windows port of ncurses called pdcurses. But if you are using visual studio there's a simple function provided called SetConsoleCursorPosition()
As you can see in u413.com: Text comes on the screen, letter by letter, which looks kind of cool,
I want to do the same thing in Console
I got the source code of version 1.2; because I dont need all the complexity of version 2;
I just need a simple Command Prompt, with text that comes on to the screen letter by letter.
I dont need most of the builtin functions offered by Console, like Transparency, Taskbar Icon, etc.
The source code base is pretty small with only about 5 files.
The main class file seems to be Console.cpp;
Since console is like a GUI application, things dont get written to the STDOUT.
but heres what happens;
A Handle is called;
And that handle apparently writes to the console;
m_hStdOut = ::GetStdHandle(STD_OUTPUT_HANDLE);
Now what I want to be able to do; Is somehow read the handle; see what text it has; And throw in a loop with a ::Sleep(20) method in it; to make sure that text appears letter by letter.
#Alf P. Steinbach I wrote the psuedo code for making the sleep command(in java) I also made use of it in every other java program I wrote, but the disadvantage was that it will work only for my programs and not every program run in the command prompt, but what I dont know is code to make a console, a windows console subsystem program, I wish it was possible with java, so that I could use it on linux too, but now, let me ask you exactly what I had in mind...
A program which simply, took input from the screen, send it to cmd.exe for processing, and sent back the reply, and all I have to do is throw in a sleep command between every character...
All I need is help, in getting this done, I wish you could start me up with this, and possible provide links and refrences to get this done...
This Console.cpp seems like a console emulator, meaning it runs OTHER programs. You don't need the source code, you can run existing console applications.
STD_INPUT_HANDLE, STD_OUTPUT_HANDLE and STD_ERROR_HANDLE are the windows handles for STDIN, STDOUT and STDERR. They basicly does the same with only a few differences in how to use it.
If you want to integrate the console into your code, then you have to understand it, and find its own output function and call that. But it won't be any standard handle or things like that.
I have a problem with my application win32 console.
The console is used to give commands to my application. However, at the same time it is used to output log messages which mostly comes from asynchronous threads. This becomes a problem when the user tries to write some input and simultaneously an async log message is printed, thus thrashing the display of the users input.
I would like to have some advice in regards to how to handle such a situtation?
Is it possible for example to dedicate the last line in the console to input, similarly to how it looks in the in-game consoles for some games?
You can use SetConsoleMode to disable input echo and line editing mode. You can then echo back input whenever your program is ready to do so. Note that this means you will need to implement things like backspace manually. And don't forget to reset the mode back when you're done with the console!
This is possible using the Console API, but it involves quite a bit of work and all the threads that use the console will have to cooperate by calling your output method rather than directly calling the Console API functions or the runtime library output functions.
The basic idea is to have your common output function write to the console screen buffer, and scroll the buffer in code rather than letting the text flow onto the last line and scroll automatically. As I recall, you'll have to parse the output for newlines and other control characters, and handle them correctly.
You might be able to get away with using "cooked" console input on the last line, although in doing so you risk problems if the user enters more text than will fit on a single line. Also, the user hitting Enter at the end of the line might cause it to scroll up. Probably best in this situation to use raw console input.
You'll want to become very familiar with Windows consoles.
Any time you have asyncronous threads trying to update the same device at once, you are going to have issues like this unless something synchronizes them.
If you have access to everyone's source code, the thing to do would probably be to create some kind of sync object that every task must use to access the console (semaphore, etc).
I have a project that I thought was going to be relatively easy, but is turning out to be more of a pain that I had hoped. First, most of the code I'm interacting with is legacy code that I don't have control over, so I can't do big paradigm changes.
Here's a simplified explanation of what I need to do: Say I have a large number of simple programs that read from stdin and write to stdout. (These I can't touch). Basically, input to stdin is a command like "Set temperature to 100" or something like that. And the output is an event "Temperature has been set to 100" or "Temperature has fallen below setpoint".
What I'd like to do is write an application that can start a bunch of these simple programs, watch for events and then send commands to them as necessary. My initial plan was to something like popen, but I need a bidrectional popen to get both read and write pipes. I hacked something together that I call popen2 where I pass it the command to run and two FILE* that get filled with the read and write stream. Then all I need to do is write a simple loop that reads from each of the stdouts from each of the processes, does the logic that it needs and then writes commands back to the proper process.
Here's some pseudocode
FILE *p1read, *p1write;
FILE *p2read, *p2write;
FILE *p3read, *p3write;
//start each command, attach to stdin and stdout
popen2("process1",&p1read,&p1write);
popen2("process2",&p2read,&p2write);
popen2("process3",&p3read,&p3write);
while (1)
{
//read status from each process
char status1[1024];
char status2[1024];
char status3[1024];
fread(status1,1024,p1read);
fread(status2,1024,p2read);
fread(status3,1024,p3read);
char command1[1024];
char command2[1024];
char command3[1024];
//do some logic here
//write command back to each process
fwrite(command1,p1write);
fwrite(command2,p2write);
fwrite(command3,p3write);
}
The real program is more complicated where it peeks in the stream to see if anything is waiting, if not, it will skip that process, likewise if it doesn't need to send a command to a certain process it doesn't. But this code gives the basic idea.
Now this works great on my UNIX box and even pretty good on a Windows XP box with cygwin. However, now I need to get it to work on Win32 natively.
The hard part is that my popen2 uses fork() and execl() to start the process and assign the streams to stdin and stdout of the child processes. Is there a clean way I can do this in windows? Basically, I'd like to create a popen2 that works in windows the same way as my unix version. This way the only windows specific code would be in that function and I could get away with everything else working the same way.
Any Ideas?
Thanks!
On Windows, you invoke CreatePipe first (similar to pipe(2)), then CreateProcess. The trick here is that CreateProcess has a parameter where you can pass stdin, stdout, stderr of the newly-created process.
Notice that when you use stdio, you need to do fdopen to create the file object afterwards, which expects file numbers. In the Microsoft CRT, file numbers are different from OS file handles. So to return the other end of CreatePipe to the caller, you first need _open_osfhandle to get a CRT file number, and then fdopen on that.
If you want to see working code, check out _PyPopen in
http://svn.python.org/view/python/trunk/Modules/posixmodule.c?view=markup
I think you've made a very good start to your problem by using the popen2() function to abstract away the cross-platform issues. I was expecting to come and suggest 'sockets', but I'm sure that's not relevant after reading the question. You could use sockets instead of pipes - it would be hidden in the popen2() function.
I am 99% sure you can implement the required functionality on Windows, using Windows APIs. What I cannot do is point you to the right functions reliably. However, you should be aware the Microsoft has most of the POSIX-like API calls available, but the name is prefixed with '_'. There are also native API calls that achieve the effects of fork and exec.
Your comments suggest that you are aware of issues with availability of data and possible deadlocks - be cautious.