login:If you see only the prompt Password: you probably used rlogin. rlogin assumes that your username is the same on all computers and enters it for you. If your username is different, don't worry, just press <CR> until you see the login: prompt and start from scratch.
At the login: prompt, type in your username. Be careful to type only lowercase! The Unix operating system is ``case sensitive.'' If you type your username in mixed case ( Rarmour rather than rarmour, for example) the computer will not recognize it.
When you first login, you should change your password with the yppasswd command. Remember again-these are lower case commands and Unix insists that you type them that way.
Your password should be longer than six characters. It's a good idea to make it mixed case or to stick some numbers or symbols in it, like ``,'' or ``^''. One of few password restrictions is that the password cannot be all-numeric (like 5534553). Because of a bug on the Sun computers, do not put a ``:'' in your password.
In the interests of self-preservation, don't set your password to your username, to ``password'' or to any information which people are likely to know about you (your real name, your nickname, your pet dog's name).
If you mistype your username or password you will get a suspicious message from the computer and see the login: prompt again.
There are a couple of files read by this shell when your login session starts up. These are the .cshrc file and the .login file. These files are created when your account is created. As you learn more about how Unix and the C shell work, you may want to customize these files.
If your files get corrupted for some reason, copies of the system defaults are available in /usr/local/skel/.
pooh>just waiting for you to type something. Throughout the Unix Tutorial section we will use % to indicate the computer's ``ready'' prompt.
% ls -aDon't actually type the % symbol! Remember, that's the computer's prompt which indicates it is ready to accept input. The spacing should be exactly as shown. ls followed by a space, followed by a -a. The -a is a ``flag'' which tells the ls program to list all files.
For more about command flags see below.
For now, use cd to change your directory to the /bin directory. Type:
% cd /binand press <CR>. Now type ls again. You should see a long list of files-in fact, if you look carefully you will see files with the names of the commands we've been typing (like ls and cd). Note that the /bin in the command we typed above was not a flag to cd. It was a ``parameter.'' Flags tell commands how to act, parameters tell them what to act on.
Now return to your login directory with:
% cdEntering cd with no parameter returns you to your home directory. You can check to make sure that it worked by entering:
% pwdwhich prints your current (or ``working'') directory. The computer should return a line of words separated by ``/'' symbols which should look something like:
/home/usernameWhatever it returns, the list should end in your username.
What man is doing is sending everything it wants to display to the screen through a program known as a ``pager'' The pager program is called more. When you see --More-- (in inverse video) at the bottom of the screen, just press the space-bar to see the next screenful. Press <CR> to scroll a line at a time.
Have you found the flag yet? The -s flag should display the size in kilobytes. You don't need to continue paging once you have found the information you need. Press q and more will exit.
There is a program file which will tell you information about a file (such as whether it contains binary data) and make a good guess about what created the file and what kind of file it is.
Only certain large directory points are partitions and the choice of these points can vary among system managers. Partitions are like the larger branches of a tree. Partitions will contain many smaller branches (directories) and leaves (files).
% du -s
% du -s -k
% ls ~usernamesubstituting in their username. You can do the same with your own directory if you've cd'd elsewhere. Please note-many people would consider looking at their files an invasion of their privacy; even if the files are not protected! Just as some people leave their doors unlocked but do not expect random bypassers to walk in, other people leave their files unprotected.
% mkdir directory-nameOnce this directory has been created you can copy or move files to it (with the cp or mv programs) or you can cd to the directory and start creating files there.
Copy a file from the current directory into the new subdirectory by typing:
copies the file from the directory above giving it the same filename: ``.'' means ``the current directory''% cd directory-name % cp ../filename .
When Charlotte Lennox (username lennox) created her directory arabella, all of the following sets of commands could be used to display the same file:
% more lennox/arabella/chapter1 or % cd lennox % more arabella/chapter1 or % cd lennox/arabella % more chapter1The full file specification, beginning with a ``/'' is very system dependent. On oceanography machines, all user directories are in the /usra partition.
Only the root account can change the ownership of a file.
The display looks something like:
protection owner group filename -rw-r----- hamilton ug munster_village
The file has ``mode'' 640. The first bits, set to ``r + w'' (4+2) in our example, specify the protection for the user who owns the files (u). The user who owns the file can read or write (which includes delete) the file.u g o rw- r-- --- 6 4 0
The next trio of bits, set to 4, or ``r,'' in our example, specify access to the file for other users in the same group as the group of the file. In this case the group is ug-all members of the ug group can read the file (print it out, copy it, or display it using more).
Finally, all other users are given no access to the file.
The one form of access which no one is given, even the owner, is ``x'' (for execute). This is because the file is not a program to be executed-it is probably a text file which would have no meaning to the computer. The x would appear in the 3rd position and have a value of 1.
% chgrp groupname filenameYou can change the protection mode of a file with the chmod command. This can be done relatively or absolutely. The file in the example above had the mode 640. If you wanted to make the file readable to all other users, you could type:
% chmod 644 filename or % chmod +4 filename (since the current mode of the file was 640)For more information see the man page for chmod.
The path is just a list of directories, searched in order. Your default .cshrc will have a path defined for you. If you want other directories (such as a directory of your own programs) to be searched for commands, add them to your path by editing your .cshrc file. This list of directories is stored in the PATH environment variable. We will discuss how to manipulate enviroment variables later.
Some commands, such as cp and mv require file parameters. Not surprisingly, cp and mv (the copy and move commands) each require two! One for the original file and one for the new file or location.
It would seem logical that if ls by itself just lists the current directory then cp filename should copy a file to the current directory. This is logical-but wrong! Instead you must enter cp filename . where the ``.'' tells cp to place the file in the current directory. filename in this case would be a long filename with a complete directory specification.
Not surprisingly ls . and ls are almost the same.
% cat .cshrcdisplays your .cshrc file to the screen. Unix allows you to redirect output which would otherwise go to the screen by using a > and a filename. You could copy your .cshrc, for example, by typing:
% cat .cshrc > tempThis would have the same effect as:
% cp .cshrc tempMore usefully cat will append multiple files together.
% cat .cshrc .login > tempwill place copies of your .cshrc and .login into the same file. Warning! Be careful not to cat a file onto an existing file! The command:
% cat .cshrc > .cshrcwill destroy the file .cshrc if it succeeds.
If you fail to give cat a filename to operate on, cat expects you to type in a file from the keyboard. You must end this with a <Ctrl>-D on a line by itself. <Ctrl>-D is the end-of-file character.
By combining these two-leaving off the name of a file to input to cat and telling cat to direct its output to a file with > filename, you can create files.
This will create a new file temp, containing the lines of garbage shown above. Note that this creates a new file-if you want to add things on to the end of an existing file you must use cat slightly differently. Instead of > you'd use >> which tells the shell to append any output to an already existing file. If you wanted to add a line onto your .cshrc, you could type% cat > temp ;klajs;dfkjaskj alskdj;kjdfskjdf <Ctrl>-D %
This would append the line echo "blah blah blah" onto your .cshrc. Using > here would be a bad idea-it might obliterate your original .cshrc file.% cat >> .cshrc echo "blah blah blah" <Ctrl>-D %
Be careful! Not all Unix editors keep backup copies of files when you edit them.
To move around you must be in command mode. You can use the arrow keys or use j, k, h, l to move down, up, left and right.
For more information type man vi. There are two reference sheets containing lists of the many vi commands available from C&C (located at Brooklyn and Pacific).
To use emacs, type:
% setup emacs % emacs
% command >& filename
When you start up you should see a message saying script started, file is typescript and when you finish the script, you should see the message script done. You may want to edit the typescript file-visible ^M's get placed at the end of each line because linebreaks require two control sequences for a terminal screen but only one in a file.
or not containing a certain string:% grep string filename % grep -i string filename (case insensitive match)
% grep -v string filenameSee the man page for grep---it has many useful options.
more and the vi editor can also find strings in files. The command is the same in both-type a /string when at the --More-- prompt or in vi command mode. This will scroll through the file so that the line with ``string'' in it is placed at the top of the screen in more or move the cursor to the string desired in vi. Although vi is a text editor there is a version of vi, view, which lets you read through files but does not allow you to change them.
When you log in, you start an interactive ``job'' which lasts until you end it with the logout command. Using a shell like C shell which has ``job-control'' you can actually start jobs in addition to your login job. But for the purposes of the most information returning programs, job (as in the ``JCPU'' column) refers to your login session.
Processes, on the other hand, are much shorter-lived. Almost every time you type a command a new process is started. These processes stay ``attached'' to your terminal displaying output to the screen and, in some cases (interactive programs like text editors and mailers) accepting input from your keyboard.
Some processes last a very long time-for example the /bin/csh (C shell) process, which gets started when you login, lasts until you logout.
The processes executing above are the C shell process and the ps command. Note that both commands are attached to the same terminal (TT), have different process identification numbers (PID), and have different amounts of CPU-time (TIME), accumulated.PID TT STAT TIME COMMAND 9980 s9 S 0:06 -csh (csh) 12380 s9 R 0:01 ps
Be careful though! This file, utmp, can get out of date if someone's processes die unexpectedly on the system. Any program which uses utmp to report information may list users who are not really logged in!
w also uses the utmp file mentioned above. It takes longer than who because it then looks around and collects more information about the users it finds in the utmp file.
Since ps doesn't use utmp it is the program to use when you really want to find out what processes you might have accidentally left on the system or if another user is running any processes. Note that although ps might report processes for a user, it might be because that user has left a ``background job'' executing. In this case you should see a ``?'' in the TT field and the user won't really be logged in.
To get this fuller listing, give the flags -aux to ps. For more information on the uses of ps, type man ps.
For more information about using finger or ways to provide information about yourself to others, type man finger.
% Mail addressMail has been changed to mailx.
You should next see a Subject: prompt. If you don't see a prompt, don't worry, just type in your one line subject anyway and press return. You may start typing your message (but you will be unable to correct errors on lines after you have pressed <CR> to move to the next line) or you may may specify a file to include with r filename.
You may invoke a text editor like vi by typing v. If you wish regularly to use an editor other than vi you should see the information later in this section about enviroment variables.
There are many other commands you may enter at this point-see the Mail man page for all of them. When you are finished typing in your message (if you have used v to run a text editor, you should exit from it) press <Ctrl>-D on a line by itself. Most likely you will now see a CC: prompt. If you wish to send copies of your message to someone besides the recipient you would enter the address or addresses (separated by ``,'') and press return. Otherwise press return without entering an address.
% write usernameand you can start writing lines to the terminal of the person you want to send messages to. The person must be logged in, and, if they are logged in more than once, you must specify the terminal to write to-for example write melville ttyh1.
To talk to users on the same computer:
% talk usernameTo talk to users on another computer use the address format of username@nodename:
% talk email@example.com
% alias ls ls -FTo list the aliases which are set for your current process, type:
% aliaswithout any parameters.
u.dat, but not
mores the files
Readme, among others
% cd ..moves you out of a subdirectory into its parent directory.
Many programs mention environment variables you may want to set for them in their man pages. Look at the csh man page for some of the standard ones.% setenv TERM vt100 % setenv EDITOR emacs
If the last command you typed was:
% ls agreenThen you can repeat this command by typing:
% !!This will return a list of files. If you saw a directory leavenworth in the list returned and you wanted to list the files it contained, you could do so by typing:
% !!/leavenworthIf you mistype leavenworth as leaveworth you can correct it with the following command:
% ^leave^leavenThis substitutes leaven for leave in the most recently executed command. Beware! This substitutes for the first occurrence of leave only!
If you are using a Sun console and you have the default setup, any xterm windows which you start up will not execute the .login.
For example, you could set a program running in the background while you edit a file in the foreground.
You should not use bg on things which accept input such as text editors or on things which display copious output like more or ps.
By default fg will return you to the process you most recently suspended. If you wanted to switch processes you would have to identify it by its job number. This number can be displayed with the jobs command. For example:
The most recently suspended job is marked with a + symbol. If you wanted to return to job one instead, you would type:% jobs  Stopped vi .login  + Stopped rn  Running cc -O -g test.c %
% fg %1You can type %1 as a shortcut.
You should always run background processes at a lower priority by using the nice command. Non-interactive jobs are usually very good at getting all the resources they need. Running them at a lower priority doesn't hurt them much-but it really helps the interactive users-people running programs that display to terminal screens or that require input from the keyboard.
If you need to run CPU-intensive background jobs, learn about how to control the priority of your jobs by reading the manual pages (man nice and man renice).
If you wish to suspend a telnet or rlogin session you must first get past the current login to get the attention of the telnet or rlogin program.
Use (immediately after pressing a return) to get rlogin's attention. <Ctrl>-Z will suspend an rlogin session.
Use <Ctrl>-] to get telnet's attention <Ctrl>-]z will suspend a telnet session. Watch out, though, if you are connected from a PC with through Kermit! <Ctrl>-] is Kermit's default escape sequence. You'll need to type <Ctrl>-] z or define Kermit's escape sequence to something else such as <Ctrl>-K.
% cp input-file-spec output-file-specwhere input-file-spec and output-file-spec are valid Unix file specifications. The file specifications indicate the file(s) to copy from and the file or directory to copy to (output). Any part of the filename may be replaced by a wildcard symbol (*) and you may specify either a filename or a directory for the output-file-spec. If you do not specify a directory, you should be careful that any wildcard used in the input-file-spec does not cause more than one file to get copied.
% cp new.c old.c % cp new.* OLD (where OLD is a directory)
% ls file-spec-listwhere file-spec-list is an optional parameter of zero or more Unix file specifications (separated by spaces). The file specification supplied (if any) indicates which directory is to be listed and the files within the directory to list.
BLOCKQUOTE> % lpr file-spec-list
where file-spec-list is one or more Unix files to be printed on the default printer. Any part of the filenames may be replaced by a wild card.
Here is more information about where the printers actually are and what kind of printers are available.
% man command % man -k topic
% more file-spec-listmore displays a page at a time, waiting for you to press the space-bar at the end of each screen. At any time you may type q to quit or h to get a list of other commands that more understands.
% mv input-file-spec output-file-specwhere input-file-spec is the file or files to be renamed or moved. As with cp, if you specify multiple input files, the output file should be a directory. Otherwise output-file-spec may specify the new name of the file. Any or all of the filename may be replaced by a wild card to abbreviate it or to allow more than one file to be moved. For example:
% mv data.dat ./research/datadat.oldwill change the name of the file data.dat to datadat.old and place it in the subdirectory research. Be very careful when copying or moving multiple files.
% rm file-spec-listwhere file-spec-list is one or more Unix file specifications, separated by spaces, listing which files are to be deleted. Beware of rm *! For example:
% rm *.dat able.txtwill delete the file able.txt and all files in your current working directory which end in .dat. Getting rid of unwanted subdirectories is a little more difficult. You can delete an empty directory with the command rmdir directory-name but you cannot use rmdir to delete a directory that still has files in it.
To delete a directory with files in it, use rm with the -r flag (for recursive).