LIS651 lecture 5 direct use of wotan

1. Thomas Krichel 2006-12-10 LIS651 lecture 5direct use of wotan

2. communication with wotan • For file editing and manipulation, we use putty. • For file transfer, we use winscp. • Both are available on the web. • The protocol is ssh, the secure shell, based public-key cryptography.

3. installing putty • Go to your favorite search engine to search for putty. • If you have administrator rights install the installer version. • Since you have already installed winscp, you should have no further problems.

4. putty options • In the window/translation choose UTF-8, always. • Find out what the size of your screen is of screen that your are using for the font that you are using, and save that in your session. • For wotan, the port is 22, ssh. • You can choose to disable the annoying bell.

5. issuing commands • While you are logged in, you talk to the computer by issuing commands. • Your commands are read by command line interpreter. • The command line interpreter is called a shell. • You are using the Bourne Again Shell, bash.

6. bash features • bash allows to browse the command history with the up/down arrow keys • bash allows to edit commands with the left/right arrow keys • “exit” is the command to leave the shell.

7. files, directories and links • Files are continuous chunks data on disks that are required for software applications. • Directories are files that contain other files. Microsoft calls them folders. • In UNIX, the directory separator is “/” • The top directory is “/” on its own.

8. home directory • When you first log in to wotan you are placed in your home directory /home/username • “cd” is the command that gets you back to the home directory. • The home directory is also abbreviated as “~“ • cd ~user gets you to the home of user user. • “cd ~” does what?

9. ~/public_html • Is your web directory. I created it with “mkdir public_html” in your home directory. • The web server on wotan will map requests to http://wotan.liu.edu/~user to show the file ~user/public_html/index.html • The web server will map requests to http://wotan.liu.edu/~user/file to show the file ~user/public_html/file • The server will do this by virtue of a configuration option.

10. changing directory, listing files • cd directory changes into the directory directory • the current directory is “.” • its parent directory is “..” • ls lists files

11. users and groups • “root” is the user name of the superuser. • The superuser has all privileges. • There are other physical users, i.e. persons using the machine • There are users that are virtual, usually created to run a daemon. For example, the web sever in run by a user www-data. • Arbitrary users can be put together in groups.

12. permission model • Permission of files are given • to the owner of the file • to the the group of the file • and to the rest of the world • A group is a grouping of users. Unix allows to define any number of groups and make users a member of it. • The rest of the world are all other users who have access to the system. That includes www-data!

13. listing files • “ls” lists files • “ls -l” make a long listing. It contains • elementary type and permissions (see next slide) • owner • group • size • date • name

14. first element in ls -l • Type indicator • d means directory • l means link • - means ordinary file • 3 letters for permission of owner • 3 letters for permission of group • 3 letters for permission of rest of the world • r means read, w means write, x means execute • Directories need to be executable to get in them…

15. change permission: chmod • usage: chmod permission file • file is a file • permission is three numbers, for owner, group and rest of the world. • Each number is sum of elementary numbers • 4 is read • 2 is write • 1 is execute • 0 means no permission. • Example: chmod 764 file

16. general structure of commands • commandname –flag --option • Where commandname is a name of a command • flag can be a letter • Several letters set several flags at the same time • An option can also be expressed with - - and a word, this is more user-friendly than flags.

17. example command: ls • ls lists files • ls -l makes a long listing • ls -a lists all files, not only regular files but some hidden files as well • all files that start with a dot are hidden • ls -la lists all files is long listing • ls --all is the same as ls -a. --all is known as a long listing.

18. copying and removing files • cp file copyfile copies file file to file copyfile. If copyfile is a directory, it copies into the directory. • mv file movedfile moves file file to file movedfile. If movedfile is a directory, it moves into the directory. • rm file removes file,there is no recycling bin!!

19. directories and files • mkdir directory makes a directory • rmdir directory removes an empty directory • rm -r directory removes a directory and all its files • more file • Pages contents of file, no way back • less file • Pages contents of file, “u” to go back, “q” to quit

20. soft links • A link is a file that contain the address of another file. Microsoft call it a shortcut. • A soft link can be created with the command • where file is a file that is already there and link_to_file is the link.

21. file transfer • You can use winscp to upload and download files to wotan. • If uploaded files in the web directory remain invisible, that is most likely a problem with permission. Refer back to permissions. • chmod 644 * will put it right for the files • chmod 755 . (yes with a dot) will put it right for the current directory • * is a wildcard for all files. • rm -r * is a command to avoid.

22. editing • There are a plethora of editors available. • For the neophyte, nano works best. • nano file edits the file file. • nano -w switches off line wrapping. • nano shows the commands available at the bottom of the screen. Note that ^letter, where letter is a letter, means pressing CONTROL and the letter letter at the same time.

23. emacs • This is another editor that is incredibly featureful and complex. • Written by Richard M. Stallman, of GNU and GPL fame. • Get an emacs cheat sheet of the web before you start it. Or look at next slide.

24. emacs commands (here ^ stands for the control characher) • ^x^s saves buffer • ^x^c exits emacs • ^g escapes out of a troublesome situation • control+space sets the mark • ^w removes until the mark (cut) • ^y pastes

25. common emacs/bash commands • ^k kills until the end of the line or removes empty line • ^y yank what has been killed (paste) • ^a get to the beginning of the line • ^e get to the end of the line

26. emacs modes • Just like people get into different moods, emacs gets into different modes. • One mode that will split your pants is the PHP mode. • “emacs file.php” to edit the file file in PHP mode. • Then look how emacs checks for completion of parenthesis, braces, brackets, and the ; and use the tab character to indent.

27. copy and paste • Putty allows to copy and paste text between windows and wotan. • On the windows machine, it uses the windows approach to copy and paste • On wotan machine, • you copy by highlighting with the mouse’ left button • you paste using the middle button • if you don't have a middle button, use left and right together

28. running mySQL • You can run mySQL in command line mode in wotan. Type mysql -u user -p • You will then be prompted for your password. The username and password are your mySQL user name and mySQL password, not your wotan user name and wotan password. • Don’t forget the semicolon after each command!

29. Thank you for your attention! Please switch off machines b4 leaving! http://openlib.org/home/krichel