Just a little bit - UNIX commands
password
- When you received your username and password from the consulting desk, the password was a generated password. You should personalize your own password so that it is easy to remember without being something others could easily guess. It should not be a word that is in a dictionary (as a program can be written to try all the words in a dictionary in seconds). Your password has to be at least 6 characters. It can be letters (UPPER case or lower case) or numbers. CHANGE IT!
type this in this is what it will do sunburst% password you will be prompted to enter your old password old password enter your old password here new password you will be asked to enter a new password new password type it again for verification
ls (list schema)
- The ls command displays the files and directories in your current working directory. If there are no visible files in your directory, the UNIX prompt will be returned. ls does not display hidden files which begin with a . (period). To display all files you must include the option -a.
type this in this is what it will do sunburst% ls displays the files and directories in your current directory sunburst% ls -a displays all files and directories (even the hidden ones) sunburst% ls -l displays all files and directories w/FULL description sunburst% dir same as ls -l (alias for DOS people) sunburst% ls -R displays all files and directories in current directory and below (recursive)
- The mkdir command will create a subdirectory inside of your current working directory. If you are logged into sunburst go ahead and try the command as follows.
type this in this is what will happen sunburst% mkdir tutor_stuff this will create a subdirectory called tutor_stuff Now let us look to make sure the directory was actually created.
sunburst% ls should display your files and subdirectories in your current working directory (including the subdirectory you just created.)
mkdir (make directory)
- The cd command will change the current working directory to the location or path you type.
sunburst% cd tutor_stuff change the working directory to tutor_stuff sunburst% cd .. cd followed by .. will take you to the current parent directory sunburst% cd cd by itself will take you to your home directory
no matter where you currently aresunburst% cd tutor_stuff change the working directory to tutor_stuff
cd (change directories)
- The touch command will update the last time a file was edited. If you touch a file that doesn't yet exist, it will create a file with zero length. You probably won't use it much, but it will allow us to easily create files that we will use and delete later.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place sunburst% touch testfile creates a file named testfile sunburst% ls check to see if the file is there Create another file of your own choice. Make sure you remember the name so you can delete it later.
touch (touches a file and updates it)
- The pwd command shows you where you are (path wise) on the computer (server - not your desktop). You have probably noticed that every time you change directories you get a description of the path. Sometimes it is necessary to know your current path without changing to a different directory.
sunburst% cd takes you to your home directory sunburst% pwd prints your working directory
you should see something like /home/coyote/usernamesunburst% cd tutor_stuff takes you to tutor_stuff subdirectory sunburst% pwd you should see /home/coyote/username/tutor_stuff See if you can get back to the more_stuff subdirectory. Next, have the full pathname printed to the screen using the pwd command. (Can you guess what the full pathname will be?)
pwd (print working directory)
- Follow the directions and make sure you understand what is happening.
sunburst% cd takes you to your home directory sunburst% ls lists files and directories in the current directory sunburst% ls tutor_stuff lists files and directories inside of tutor_stuff sunburst% ls what is not a directory and will say "what not found" sunburst% ls ~ lists files and directories in your home directory
(no matter where you currently are in the system)
Miscellaneous stuff about directories and pathnames
- You can make an exact copy of a file using the copy (cp) command.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place sunburst% cp testfile file2 makes a copy of testfile and calls it file2 sunburst% dir make sure the files are really there
cp (copy file)
- The mv command moves files and directories around in the file system. You can also use the mv command to rename a file. To make sure these examples work you must be inside of tutor_stuff with the testfile and file2 created.
sunburst% mv testfile file1 renames testfile with the name of file1 sunburst% mv file1 .. moves file1 to its parent directory sunburst% mv file2 more_stuff moves file2 into subdirectory more_stuff
mv (move file)
- The rm command removes or deletes files from the file system. You must be careful. DO NOT delete anything you might need later. You can't get it back.
sunburst% rm file1 removes file1 sunburst% rm file3 .. removes file3 Check to see that file2 still exists and that file1 and file3 are gone. Then remove file2.
rm (remove file)
- The rmdir command will remove an empty directory. If you have followed closely up to this point you should not have any files in the subdirectory more_stuff, so let's remove that directory.
sunburst% cd ~/tutor_stuff makes sure everyone is in the right place sunburst% rmdir more_stuff removes directory called more_stuff
rmdir (remove directory)
- The chmod command lets the owner of a file change the permissions settings for a file or directory. These permissions are displayed with the dir or ls -l listings. The permissions are in the form of
This collection of letters tells us how the permissions for a file (starting with a -) or directory (starting with a d) are set. The first three letters give the permissions for the owner of the file. The middle group (next three letters) give us the permissions for the group to which the owner belongs. The last three letters tell the permissions for everyone else. The permissions can be set for directories as well as files but have slightly different meanings.- r-permission to list files in a directory
- w-permission to delete files or move files
- x-permission to access to files in the directory
permissions owner group everyone - rwx rwx rwx codes r - Read Permission 4 w- Write Permission 2 x- Execute Permission 1
chmod (changing a file mode)
- The du command prints the number of kilobytes you have in each subdirectory. This can be useful to see which directory has the most files if you have gone over quota. From your home directory type
sunburst% du
du (disk utility)
- Each user on sunburst is allocated a certain amount of disk space (usually about 5 megabytes). If you exceed this quota some of your files must be removed within a certain time period. To check your quota and see how much you are using type
sunburst% quota -v
quota (displays user quota and usage)
- The command clear just clears your terminal screen. Go ahead and try this. You should see a clear terminal window with sunburst% at the top.
clear (clears screen)
Ways to display file contents
- In order for us to experiment with the next five commands, we need to create an example file. To do this you can either type the list below exactly as it appears or you can highlight (or select) the list below and cut-n-paste it into UNIX at the sunburst% prompt. Either way will work the same. In this example we are sending the input from the keyboard into the file demofile. AFTER the list is either typed into UNIX or pasted from Netscape into UNIX you must stop the input with a return and a control-d.
---------------------------list below
cat > demofile
one
two
three
four
five
six
seven
eight
nine
ten
eleven
twelve
thirteen
fourteen
fifteen
sixteen
seventeen
eighteen
nineteen
twenty
twenty-one
twenty-two
twenty-three
twenty-four
twenty-five
twenty-six
- The cat command will display the entire contents of the file on the terminal screen. If it is more than one page it will all scroll by quickly.
sunburst% cat demofile displays entire file contents to terminal screen
cat (concatenate)
- To display the entire file one screen at a time use the more command instead of cat. After each screen is drawn you must hit the space bar to go on to the next screen.
sunburst% more demofile displays the file example one screen at a time
more (display one screen at a time)
- The head command will display the first 10 lines of a file.
sunburst% head demofile should display one - ten in our demofile
head (display first 10 lines of a file)
- displays last 10 lines of a file
sunburst% tail demofile should display seventeen-twenty-six in our file
tail (displays last 10 lines of a file)
- The wc command will tell you how many lines, words and characters.
sunburst% wc demofile would return 26 lines 26 words and about 170 letters
If you pasted the info from Netscape there would be a few more letters because of additional spaces used in formatting HTML (approximately 383 letters).
wc (word count)
- The * is a wild card that will replace anything in its place. Below are some examples of its use.
sunburst% dir *.gif displays all files ending with .gif sunburst% dir test* displays all files beginning with test
* (wild card - matches none or more )
- The ? is a wild card that will match one character only. Below is an examples of its use.
sunburst% dir test?.gif displays all files starting with test
then valid character
then ending with .gif
would not find test10.gif
? (wild card - matches just one character)
- Unix file names should contain only letters, numbers, underscore and period (. often referred to as dot). The file names can contain up to 256 characters. Try to give your file names meaning. Don't use all 256 characters.
file name conventions
- This is called the bang bang command. It will repeat the last command entered into unix from your keyboard. This is like the F3 command from DOS.
sunburst% dir would display the current working directory sunburst% !! would repeat last command sunburst% mkdir stuff creates directory stuff sunburst% clear clears the terminal window sunburst% cd stuff change working directory to stuff sunburst% !c would try to change directories again
this wouldn't work because you are already theresunburst% !cl would send the last unix command starting with cl which would be clear
!!
More help directly from UNIX here
- Read the UNIX on line manual page for a specific command.
sunburst% man cp displays online manual for copy command
man
- The whatis command will display a one-line explanation of a command.
sunburst% whatis cp displays a one-line description of the cp command
whatis
- If you don't remember the UNIX command but you know you want to copy a file you can use the apropos command to find reference to the copy command within the online manual.
sunburst% apropos copy displays references to copy within the online manuals
apropos
A little fun?
- If you want to find out some information about another user (such as: are they logged on, when did they read their mail last, do they have a plan) you can use the finger command. The finger command reads some of those invisible files in your directory we were talking about earlier to display the information you will see on your screen.
sunburst% finger username@host displays information regarding the person you are checking on
finger
- If you fingered someone and know that they are currently logged into sunburst you can talk to them. The talk command will split your window into a upper portion and lower portion. You will type on one and read the person's responses an the other port ion. It is kind of like a telephone (well no sound). You can do this with anyone in the world that is logged on if you know their e-mail address.
After you issue the talk command the other person should see a message that says you are requesting to talk to them. If they want to talk to you they need to type in a corresponding message on their computer screen.
sunburst% talk username@host allows you to talk to someone else over internet
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