UNIX Primer


Logging on to the system

 From the PC's in 301, 302, or 303
  1. If the Command Prompt icon is not on the desktop or the Start menu, navigate to Start --> Programs --> Accessories --> to Command Prompt. Opening this will start a text window.
  2. At the prompt, type in telnet frodo.cis.ysu.edu. This will connect you to frodo, causing the window to act as a terminal emulator.
  3. Enter your login name and password when prompted.

Logging out
To exit Frodo and return to the PC, type logout at the frodo prompt. Do not forget to do this before leaving lab.

Changing your password

It is recommended that you change your password on a regular basis. To do so, use the Unix command passwd.

You will be prompted for both your old password and the new one (twice for confirmation). Remember that you password should be at least 6 characters long, should not be any word in the English language, and should contain at least 1 digit or other non-alphabet character.

Getting help in UNIX

The man command is useful to get more information about any command in UNIX. For instance, to find out more about the ls command, you would type

man ls

The apropos command can help you find commands related to some keyword. For instance

apropos copy

would list all UNIX commands related to copying (including cp).

File and Directory Manipulation

Listing your files
ls lists all files in your directory (like dir)
ls -l show all attributes (such as size, date created, and permissions)
ls -a list all files (including those that begin with . )

Copying and deleting files
cp file1 file2 copies file1 into file2
rm file deletes file
Note that unlike windows, you are not asked for confirmation when a file is deleted!

Directories and subdirectories

As in Windows, your Unix files may be organized into directories and subdirectories for the purpose of good organization. The syntax is roughly the same as in DOS (note, however, that UNIX uses the forward slash / instead of the backslash for subdirectories).

Creating directories
mkdir directory creates a new subdirectory called directory

Changing the current directory
Like DOS, you can navigate through your directories using the cd command.

cd directory takes you to directory (if it is a subdirectory of the current one)
cd .. takes you back up to the directory of which your current directory is a subdirectory
cd returns you to your root directory.

Copying and directories
You can also copy and move files from one directory to another using cp. For example:
cp file directory will make a copy of file in directory directory (as long as directory is a subdirectory of your current location).
cp directory1/file directory2 will copy of file from directory1 into directory directory2.
cp ../file1 file2 Will copy file1 from the directory below the current one, into

Printing

To print out a file, use the following command:

lp -d p30xy filename

where
filename is the file you wish to print,
x is the last digit of the room you are in (either 1, 2, or 3),
y is either a, b, or c.

For example, to print prog1.c to printer a in room 301, you would type:

lp -d p301a prog1.c

Setting Permissions for Files and Directories

One of the important things to understand about a multiuser system like UNIX is that all files are stored on the same machine, and that you could (theoretically) reach anyone else's directory and files by doing cd .. enough. This makes it important to control the permissions for your files.

This is done in UNIX with the chmod command. It has the basic syntax: 

chmod who op ability
where who is some combination of:
uThe owner of the file (that is, you).
gThe group you belong to (not relevant now, but will be later when you work on group projects).
oAll others.

where op is either:
+Add this ability to these people.
-Remove this ability to these people.

where ability is some combination of:
rThese people can read this file.
wThese people can write to this file.
xThese people can execute this file (or cd into it, if it is a directory).
For example: 

chmod o-r fred
means that others can no longer read the file fred. 
chmod o+x barney
means that others can now enter the directory barney.