I have maybe a strange question: is there a way to embed something like the Linux command line in an application? Specifically I'm imagining hacking games like Uplink where there's a command prompt in-game that you interact with. They're sometimes done well but often not, since writing a command line interpreter is a lot of work on top of making a game. If there was a way to leverage actual command line tools that would both cut out a lot of work for the developer and also help with immersion (it's a Unix system, I know this!).
It would need to be something like a sandboxed virtual machine, since you wouldn't want it to interact with the real host machine, just a fake in-universe computer. But it'd still be nice to support things like bash.rc, piping commands, foreground and background tasks, and keyboard shortcuts.
I'm imagining something like how Lua embeds in C, where you'd get callbacks in the host application when the virtual linux machine wanted to interact with the console, read/write files or start up threads.
But I don't know if anything like this exists, or even can exist without more effort than it'd be worth? I'm not even sure exactly what terms to google to start researching this.
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This one is a pretty strange question of mine so I'll try to explain the best I can.
On a DOS Linux distribution, without having installed any graphical environment, if I start an application which is supposed to have a GUI, will I be able to interact with that window via code?
What I thought is that if KDE/GNOME's role is to graphically represent an existing GUI, I should be able to interact with it but if these graphical environments have an active role in the window creation there is nothing I can do.
You won't be able to run a graphical program without a window manager.
The reason is that the window manager is doing a lot more than just allowing the window to be shown to the user. It comes with libraries and services for constructing windows and components and interacting with them. Without these libraries and services, the program won't be able to start.
The only exception would be if a program contained all the graphical code built into it, and didn't rely on a window manager. Realistically this would only happen for a fairly simple program and in special cases; for instance, Raspbian includes OMXPlayer, which shows full screen video without relying on any window manager.
Quoting (with some adaptation) from https://raspberrypi.stackexchange.com/a/3974 which answers how to start mplayer in X11 without a window manager:
The X server is really usually called X and you can just start it. You can set the DISPLAY number as an argument along with some other things.
You might want to have some sort of session, though, and still go through xinit or such and start X with startx. You can use .xinitrc or such as a script and simply not start a window manager there. You will need a "magic client" as the last command that stays running so X doesn't terminate immediately. In a traditional "failsafe" session, that was an xterm. If you know what to launch and launch once only, it could be that program or any UI/wrapper that does the launching for you. When the last ("magic") client in the init script terminates, X terminates.
If all you want to do is play video, you might see if you can run mplayer with directfb instead and skip using X11 entirely.
I want to make a system which would get input from USB barcode scanner, validate it on remote server and display an answer (text and images).
I would use JavaFX or in-browser JS web application to grab scanner input somehow.
I'm planning to run this application on Raspberry Pi or plain PC.
Is there a way (or a special linux distribution) to ensure that system always loads the same way and starts JavaFX app or opens particular web page in browser?
e.g. no login page, NO update or other popups are shown.
Any other ideas? Thanks
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Found an interesting solution here, where JavaFX GUI app is started from command line, without X-Server(linux graphical interface) at all.
I have recently done something similar, and it's not too hard. Obviously working on the Pi, you will want to use something like Linux and having limited hardware will mean that you should be minimising what you are running. Due to this, I would recomend that you run a light weight distro. Something like arch (which is what I used) allows you to build only what you want from the ground up without the need to find and compile everything like you do for LFS or Gentoo.
As for booting, the following two wikis will give you the details of starting the Gui without manual login:
https://wiki.archlinux.org/index.php/Automatic_login_to_virtual_console
https://wiki.archlinux.org/index.php/Start_X_at_Login
After that, it is simply a matter of putting the command to launch your program in .xinitrc.
I'll start with a little background. A small project of mine has been to try to use my Android tablet as an external monitor for my laptop using a VNC client (vnc4server). There are two main options for doing this that I have seen. The simplest is to use xrandr and widen the screen, creating a section just for the tablet. However, this can cause some graphics issues if I understand correctly, although it has the benefit of permitting windows to cross displays. The other option is to run a separate desktop session for the VNC server.
I have chosen to go the route of a second desktop as the session can live and die without significantly affecting my main session and can in theory be tailored specifically to the tablet. A little tool called x2vnc allows me to connect to the VNC server in a similar manner to the more popular Synergy and use it like a n external monitor. I also have the nice little benefit of being able to easily and cleanly switch from landscape to portrait using xrandr.
This brings me to my current issue. So far, I have only been able to reliably use plain x-windows. Although this is entirely functional, I would prefer something more complete. Although xstartup examples have been posted for a variety of window managers, none of these seem to run properly. I suspect all of these are for headless systems. Gnome/Unity are each unforgivably slow and seem to conflict with my existing session. I also feel that these are a little too cluttered for my ten inch tablet. On the other hand, Xmonad simply crashes as soon as I try to open a second window in addition to not updating the graphics properly.
I would like to know anything that will lead me in the direction of a better stable desktop environment. This includes configuration tips and alternate window managers.
I am currently running Ubuntu 12.04 with gnome-xmonad (recently Unity). My xstartup is plain x-window-manager. I have tried any readily available examples for gnome and xmonad that I have been able to find.
I'll start off by saying I'm no Linux guru, or even close. I use it to develop embedded applications and it serves my purposes just fine as such.
I have a program which is running (I suppose the correct terminology is "running in a terminal") on a CentOS 6.3 box. For debug and statistics, I have a routine which monitors the keyboard (stdin file) and spits out items as requested by the given key-presses. That all works fine when I'm sitting in front of it.
But I'd like to be able to perform these simple functions: press a key, see some output, remotely. I can SSH into the box and execute commands, but I can't "see" this program.
I have tried searching "communicating with other terminals using ssh" and myriad variations, but I guess I'm not asking this correctly -- the search results are worthless.
What I'd like to be able to do is login to my account and then somehow "see" my program running and type keys and see its output. Is this a stdin/stdout redirection issue?
I apologize in advance if this is painfully obvious and I'm just an idiot, but I'd still like to know how to do it... :)
If you use the linux 'screen' utility, you can re-attach to the original terminal session that you used to start the program. basically you just type screen and then run your program. here is more useful info on screen:
http://www.rackaid.com/resources/linux-screen-tutorial-and-how-to
I have some knowledge of CGI scripts and how they work and came to thinking that, in theory, it should be possible to run VirtualBox, or any type of virtualization as a CGI script. Understandably, this would be no easy task. For one thing, it's output (the screen of the virtual OS) would somehow have to be converted so that the browser could read it, show it to the user, and then somehow update it without refreshing the page (which would mean JavaScript would be involved, probably).
Does anyone have any suggestions on how one would start a project such as this one? Has this been done/attempted before?
First of all, running a virtual machine as a CGI script is highly unpractical, as it would stop the machine if the connection is broken. Instead, the CGI script should be able to start, stop and control the virtual machine, which would be running in the background.
As for interacting with the virtual machine, VirtualBox has support for remote desktops (through the VNC protocol), which is probably the most suitable method of displaying and controlling it. However, while you can use a combination of server-side and client-side scripting to make this work, this would probably become very slow and use a lot of bandwidth. Instead, you could use something like a Java applet to connect directly to the virtual machine via VNC, which would save much of the hasstle on the server side.
There is also a similar idea called phpvirtualbox, which I haven't look into myself, but you might find it interesting.