Just Enough UNIX

1. Just Enough UNIX

2. UNIX Operating System • Generally operates from a command-line. • After logging on, met with command-prompt: • gridx: • In labs, you will be using X-windows on X-terminals.

3. UNIX commands • All UNIX commands are actually programs. • You “run” a program by typing its name at the command prompt. • Generally, the output of a program goes to the screen and if the program requires any input, it gets it from the keyboard. • These are called: • stdout & stdin

4. File navigation and manipulation • UNIX uses a hierarchical file structure. • Very similar to Windows and Macintosh. • Directories not folders. • Move about with typed commands rather than mouse-clicks.

5. ls list Displays the names of the files in the current directory. Flags: -a: shows all the files, including hidden ones -F: puts a / after directories, an * after executables, and an @ after links -l: displays a long listing of files

6. pwd print working directory Displays the full path of the current directory you are in. e.g.: /home/CS/cs153/801/skea1234/programs

7. cd • change directory • Changes your working directory to whatever you specify. • cd [name of directory] • Without any directory (just cd) you will be taken to your home directory. • cd • With .. you will be taken to the parent of the working directory • cd ..

8. cp copy Copies the contents of one file to another. cp [file to copy] [new file name] Copies a file from one directory to the working directory cp [path of file to copy] .

9. mv move Better name could be the rename command. Changes the name of one file to another. mv [old file name] [new file name] Note that the [new file name] could be a directory, which will effectively move the file to the new directory keeping the original name.

10. rm remove Deletes the specified file or files. This is destructive! They are gone! They cannot be retrieved!!! rm [file name] Note: this does not generally work with directories.

11. mkdir make directory This creates a directory. mkdir [new directory name] Does not automatically change to the new directory after it is created.

12. rmdir remove directory This deletes a directory (as opposed to the rm command above). The directory must be empty otherwise you will get an error.

13. man • UNIX reference manual • Gives usage, options, examples for UNIX commands and applications • man [command name] • $: man pwd • $: man man • Option –k searches the manual pages by keyword • $: man –k “working directory”

14. Access privileges • All UNIX files have privileges associated with them. • These privileges determine who can access the file. • These privileges determine how people can access the file.

15. Viewing access privileges • Use the ls -l command. drwx------ 2 jimd 8192 Jul 12 12:26 nsmail/ -rw-r--r-- 1 jimd 945 Mar 15 16:01 old.cshrc -rwxrwxrwx 1 jimd 168 Jan 13 1998 file.exe -rw-rw-rw- 1 nobody 382 Nov 18 1998 old.profile -rw------- 1 jimd 652 Jul 12 12:16 old.xsession drwx------ 2 jimd 8192 Jun 23 13:21 thesis/ -rw-r--r-- 1 jimd 1186776 Jul 13 15:07 win32tutorial.ps

16. Types of file access - rwx • Read — person can look at the contents of the file. • Write — person can change the file. • eXecute — person can execute the file (applies only to directories and program).

17. Types of users - ugo • User/owner -- the person who owns/created the file. • Group — UNIX allows for the creation of groups. • Others/world -- everyone else in the world that has access to that computer.

18. To change permissions chmod — changes the access mode of a file. Two methods exist symbolic absolute

19. chmod - absolute • Absolute - you specify a numeric equivalent for a set of permissions. • You specify all permissions at once.

20. chmod - absolute • chmod [xxx] [file] • Where each x is some number from 0 - 7. • Each number specifies a level of privileges for a specific group.

21. chmod - absolute • e.g., chmod 644 index.html User permission World permission Group permission

22. chmod - absolute • Permissions: • Read = 4 • Write = 2 • Execute = 1 • Set permissions by adding the values of all the permissions you wish to set.

23. chmod - examples • To give yourself read & write permission and no permission to anyone else: • chmod 600 foobar.txt • To give yourself read & write permission and everyone else read permission only: • chmod 644 index.html • To give yourself full access to a directory, and everyone else read & execute permission only: • chmod 755 images

24. chmod - symbolic • symbolic - you specify only the changes to be made to the permissions • You specify changes for only one user-type.

25. chmod - symbolic • chmod [user-type + or – rwx] • Where + signifies adding permission and - signifies removing permission • rwx - include only the permissions to by updated.

26. chmod - symbolic • e.g., • e.g., chmod g+rw index.html User-type Permissions changed Change to be made

27. chmod - examples • To add read & write permissions for yourself: • chmod u+rw foobar.txt • To remove write and execute permissions for everyone who is not user or group: • chmod o-wx images • To add write permissions for the group: • chmod g+w index.html