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Top Forums UNIX for Dummies Questions & Answers Difference between console and Terminal. Post 302508076 by Corona688 on Friday 25th of March 2011 03:49:40 PM
Old 03-25-2011
Quote:
Originally Posted by theKbStockpiler
Terminal Commands: Control-Alt-F7

After login:
gedit (enter) (gedit: 3684) GTK-Warning**: cannot open display:

kate (enter) cannot connect to X Server
I take it you're running that from a raw text console? Only things that logged in through your X server will have access to X these days.
Quote:
I'm wondering if just Getty starts a bash shell and everything else is a kernel driver.
Yes. That's literally all there is to it (in userspace, anyway).
Quote:
I thought unless X ran it , the application (bash shell) used direct system calls.
BASH always uses direct system calls. read() and write() are direct system calls. Smilie

The shell doesn't care whether it's in a GUI or a real terminal. The kernel does all the legwork and makes them act the same.

IOW, what changes is what these system calls talk to. In a graphical terminal, the shell is probably talking to a virtual terminal device. That's something like an anonymous pipe -- user programs can create and destroy them -- but they have terminal behaviors added on. Also, they're bidirectional. Writing Ctrl-C into it causes SIGINT to anything belonging to it, etc, etc. The graphical program(i.e. xterm) reads what the program writes and draws it on the screen, and writes what you type into the keyboard into the terminal device for the shell to read and process.

A raw text terminal is a real terminal. It physically exists. Nothing had to create it, it was there all along as far as userspace is concerned, and it can't be destroyed. The kernel does it all. No intermediate program draws on the screen.

For that matter, a VGA terminal is pretty close to actually being a raw terminal. When you type 'a', the kernel doesn't need to do much more than stick the raw byte 'a' in video memory. Fancy framebuffer terminals are a bit more complicated(and slower), though still handled in the kernel. They're complicated and finicky enough that I'm not convinced they really belong in the kernel either.

Another kind of 'real' terminal is a serial port. Technically all terminal devices, real and virtual, act like serial ports. Try 'stty' in a GUI login -- it'll report a baud rate and everything! The baud rate does nothing in anything that's not a real serial port of course, but most of the other myriad options can still be configured to your liking.

Last edited by Corona688; 03-25-2011 at 09:03 PM..
 

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ports(7)						 Miscellaneous Information Manual						  ports(7)

NAME
ports, port_names - Device (tty and lp) names for serial and parallel ports SYNOPSIS
Default Serial Ports: /dev/tty00 /dev/tty01 (not present on a single-port system) Parallel Port: /dev/lp0 DESCRIPTION
AlphaStation and AlphaServer systems provide one or two 9-pin serial communication ports. These ports are usually labelled 1 (COMM1) and 2 (COMM2), but they may be identified by different icons. Using the appropriate serial cable and terminator, you can connect a serial printer, external modem, or character-cell terminal to a serial port. Most AlphaStation and AlphaServer systems also provide one parallel port, for use with a parallel printer. When you add a device to your system, the installation documentation may instruct you to map the device pathname to the port. These devices are located in the /dev directory. For serial-line ports, the two default device pathnames are: This pathname always maps to 1, COMM1, the lowest port number, an icon for a terminal console, or the only serial port (on a single-port system). This pathname always maps to 2, COMM2, the next numbered port, or (if one serial port is labeled with an icon for a terminal console) the remaining serial port. If your system hardware has been extended to include additional serial ports, the pathnames /dev/tty02, /dev/tty03, and so forth, may also be available to you. However, most systems have only /dev/tty00 and /dev/tty01 as the device pathnames for serial ports. The one parallel port on an AlphaStation or AlphaServer may be labeled with the word printer or a printer icon. On some systems, the paral- lel port may not be labeled. The device pathname for the parallel port is /dev/lp0. Currently, Tru64 UNIX does not fully support parallel printers, so fewer devices are connected to this port as compared to serial ports. If you are connecting a terminal console to your system, it must be connected to the serial port mapped to /dev/tty00. For other serial devices, it does not matter which of the serial ports you choose for the connection. For example, suppose you are setting up a system that has two serial ports, labeled 1 and 2. You intend to use a serial-line terminal rather than a workstation monitor as the system console and also want to connect a serial-line printer to the system. In this case, you must connect the terminal to the port labeled 1 (with the device pathname /dev/tty00). Therefore, you must connect the printer to the remaining port labeled 2 (with the device pathname /dev/tty01). If, for the same type of system, you intend to use a workstation monitor as the system console, it does not matter which serial port you use for a serial-line printer or modem. In other words, you can connect the printer to either port 1 (with pathname /dev/tty00) or port 2 (with pathname /dev/tty01). When prompted to enter a /dev/tty** pathname by the lprsetup script or the Print configuration tool in the CDE Application Manager, you would specify /dev/tty00 if you connected the printer to port 1 or /dev/tty01 if you connected the printer to port 2. See the System Administration manual for more information on setting up consoles (including remote consoles) and printers. See the modem(7) reference page for more information on setting up modems. SEE ALSO
Commands: lprsetup(8) Devices: ace(7), modem(7) System Administration delim off ports(7)
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