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Linux Terminal System

Linux Terminal System. Conceptual Linux terminal Terminal API Terminal emulators Graphical user interfaces. Conceptual Linux terminal. Mainframe. Terminal. User. Application. Keyboard. Kernel. Display. Modem. Modem. stdin/stdout. Low-level calls: read(), write(), fd's

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Linux Terminal System

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  1. Linux Terminal System • Conceptual Linux terminal • Terminal API • Terminal emulators • Graphical user interfaces

  2. Conceptual Linux terminal Mainframe Terminal User Application Keyboard Kernel Display Modem Modem

  3. stdin/stdout • Low-level calls: read(), write(), fd's • High-level calls: fread(), fwrite(), FILE*'s • Formatted I/O: fscanf(), fprintf(), FILE*'s • Redirection: dup2(), pipes “|”, redir “>” $ randomize < input | rot13 | tee log | rot13 | sort $ cat log randomize rot13 tee rot13 sort input log cat terminal

  4. Escape sequences & function keys Application Escape sequences “\e[2J” = clear screen Terminal • Many incompatible escape sequences and terminal capabilities • $TERM identifies terminal type • termcap/terminfo defines terminal types Function key sequences “\e[A” = up arrow key

  5. ioctls and termios • ioctls give very low-level access • termios standardizes interface • ioctls/termios can adjust canonical (cooked) and non-canonical (raw) modes • Linux terminal provides font, etc. ioctls • Serial ports have baud rate, etc. ioctls

  6. curses, ncurses, and S-Lang • Wrapper libraries hide complexity of terminal programming • Provides portable interface to many terminal types • curses: cursor control library • ncurses: new curses • S-Lang: contains terminal control library

  7. Terminal emulators • Consumer computer systems have integrated human interface hardware, so terminal functionality must be emulated • Dumb terminal: works like a teletype • Linux vt100: VGA + keyboard + buzzer • GNU screen: display multiplexing • xterm: text terminals in graphical display

  8. X Window System • X server gives programs access to keyboard, mouse, and display hardware • Client apps tell the server what to draw • User sits in front of X server Mainframe Mainframe X server User X app 1 X app 2 Kbd/VGA

  9. VNC: Virtual Network Computing • Cross between GNU screen and X • User sits in front of VNC client (“viewer”) Mainframe Mainframe Workstation User gimp wmaker XFree86 Xvnc xterm vncviewer

  10. Conclusion • Archetypical Linux terminal system • Program input and output • Terminal API, low- and high-level • Terminal emulators • Graphical user interfaces Slides available online: http://ioioio.net/school/terminal/slides.pdf

  11. GNU screen

  12. VPN over SSH

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