1. Introduction to UNIX

2. 2 Introduction What is UNIX?  UNIX is an operating system which was first developed in the 1960s, and has been under constant development ever since. By operating system, we mean the suite of programs which make the computer work. It is a stable, multi-user, multi-tasking system for servers, desktops and laptops.  UNIX systems also have a graphical user interface (GUI) similar to Microsoft Windows which provides an easy to use environment. However, knowledge of UNIX is required for operations which aren't covered by a graphical program, or for when there is no windows interface available, for example, in a telnet session. Types of UNIX  There are many different versions of UNIX, although they share common similarities. The most popular varieties of UNIX are Sun Solaris, GNU/Linux, and MacOS X..

3. Introduction to UNIX 3 The UNIX Operating System The UNIX operating system is made up of three parts; the kernel, the shell and the programs. The kernel  The kernel of UNIX is the hub of the operating system It allocates time and memory to programs and handles the filestore and communications in response to system calls.  An illustration of the way that the shell and the kernel work together suppose a user types rm myfile (which has the effect of removing the file myfile) The shell searches the filestore for the file containing the program rm, and then requests the kernel, through system calls, to execute the program rm on myfile When the process rm myfile has finished running, the shell then returns the UNIX prompt % to the user, indicating that it is waiting for further commands.

4. Introduction to UNIX 4 The UNIX Operating System The shell  The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called the shell. The shell is a command line interpreter (CLI) - it interprets the commands the user types in and arranges for them to be carried out. The commands are themselves programs; when they terminate, the shell gives the user another prompt (% on our systems).  The adept user can customize his/her own shell, and users can use different shells on the same machine.  History - The shell keeps a list of the commands you have typed in. If you need to repeat a command, use the cursor keys to scroll up and down the list or type history for a list of previous commands.

5. Introduction to UNIX 5 Files and processes Everything in UNIX is either a file or a process.  A process is an executing program identified by a unique PID (process identifier).  A file is a collection of data. They are created by users using text editors, running compilers etc. Examples of files:  a document (report, essay etc.)  the text of a program written in some high-level programming language  instructions comprehensible directly to the machine and incomprehensible to a casual user, for example, a collection of binary digits (an executable or binary file);  a directory, containing information about its contents, which may be a mixture of other directories (subdirectories) and ordinary files.

6. Introduction to UNIX 6 The Directory Structure All the files are grouped together in the directory structure. The file-system is arranged in a hierarchical structure, like an inverted tree. The top of the hierarchy is traditionally called root (written as a slash / )

7. Introduction to UNIX 7 The Directory Structure In the diagram below, the home directory of the undergraduate student "ee51vn" contains two sub-directories (docs and pics) and a file called report.doc. The full path to the file report.doc is "/home/its/ug1/ee51vn/report.doc"

8. Introduction to UNIX 8 UNIX at BC – SSH Secure Shell Client The preferred connection method is SSH (Secure Shell Client) which does not transmit your password in the clear across the internet, as telnet and ftp do.  SSH includes sftp ( Secure File Transfer Protocol ) and scp ( Secure Copy ). See the Andersen textbook for more details. If you are running a Linux, Unix or Mac system, ssh is probably available on your system. For MS windows users install packages are available at:  http://acc4.its.brooklyn.cuny.edu/~sysadm/ssh/win/SSHSecureShellClient-3.2.9.exe http://acc4.its.brooklyn.cuny.edu/~sysadm/ssh/win/SSHSecureShellClient-3.2.9.exe  http://acc6.its.brooklyn.cuny.edu/~sysadm/ssh/win/SSHSecureShellClient-3.2.9.exehttp://acc6.its.brooklyn.cuny.edu/~sysadm/ssh/win/SSHSecureShellClient-3.2.9.exe  ftp://acc5.its.brooklyn.cuny.edu/pub/sysadm/SSHSecureShellClient-3.2.9.exe These Windows products are licensed for use by Brooklyn College only. Using one of the lab's Unix machines, the command "lab_machines" will return a list of available Unix machines. i.e.  atrium11.its.brooklyn.cuny.edu 146.245.252.11 atrium12.its.brooklyn.cuny.edu 146.245.252120 acc2.its.brooklyn.cuny.edu 146.245.252.72 fldsun228.its.brooklyn.cuny.edu 146.245.252.228

9. Introduction to UNIX 9 UNIX at BC - SSH Once SSH is installed, click on the icon and SSH Secure Shell (left) will appear Click on the “Quick Connect” icon; this will bring up the “Connect to Remote Host” popup  Enter the Host Name (e.g., atrium96.its.brooklyn.cuny.edu) and User Name and click Connect  You will be prompted for your password  Another popup will allow you to name the profile information for future reference

10. Introduction to UNIX 10 UNIX at BC - SSH Now you’re connected at ready to roll

11. Introduction to UNIX 11 UNIX at BC – SSH Transfer To transfer files between your local PC and the Unix machines, click on the SSH Secure File Transfer icon  Click on Quick Connect and follow the same procedure as in connecting with SSH Shell  You will have two windows – one for your local machine and one for the Unix server. Drag and drop files from one to the other

12. Introduction to UNIX 12 UNIX at BC - Telnet Open a browser and enter the url telnet://atrium4.its.brooklyn.cuny.edu/ telnet://atrium4.its.brooklyn.cuny.edu/ This will open a DOS window, connect you to the college’s SUN servers and prompt you for an id and password When completed, you will see a prompt of the form $ atrium4:/users1/rudowsky> Now you’re in business

13. Introduction to UNIX 13 UNIX at BC See David Arnow’s “Getting Started with UNIX” guide Basic commands:  ls [-a|-l] List files in the directory  mkdir make a directory  rm remove a file  mv rename a file  cat display a file  cp copy a file  command > redirect the output of a command e.g., ls –l > list  g++ xyz.cpp –o xyz compiles a C++ program named xyz.c and saves the compiled progam as xyz  exit

14. Introduction to UNIX 14 UNIX at BC ls does not, in fact, cause all the files in your home directory to be listed, but only those ones whose name does not begin with a dot (.) Files beginning with a dot (.) are known as hidden files and usually contain important program configuration information. They are hidden because you should not change them unless you are very familiar with UNIX!!! To list all files in your home directory including those whose names begin with a dot, type ls -a

15. Introduction to UNIX 15 UNIX at BC When you type ls -a in a directory, two special directories called (.) and (..) appear In UNIX, (.) means the current directory, so typing cd. means stay where you are  NOTE: there is a space between cd and the dot (..) means the parent of the current directory, so typing cd.. will take you one directory up the hierarchy  Note: typing cd with no argument always returns you to your home directory. This is very useful if you are lost in the file system. Pathnames enable you to work out where you are in relation to the whole file-system.  For example, to find out the absolute pathname of your home-directory, type cd to get back to your home-directory and then type pwd pwd (print working directory)

16. Introduction to UNIX 16 UNIX at BC Home directories can also be referred to by the tilde ~ character. It can be used to specify paths starting at your home directory.  ls ~/unixstuff will list the contents of your unixstuff directory, no matter where you currently are in the file system  ls ~ will list the contents of your home directory no matter where you currently are in the file system  ls ~/.. will list the contents of the parent of your home directory no matter where you currently are in the file system

17. Introduction to UNIX 17 Your Directory Structure Your assignments should be maintained in a directory tree with the following structure:  Directly beneath your home directory, there should be a subdirectory named cis15.  Directly beneath cis15, there should be a subdirectory named homework Within homework, there should be a subdirectory for each assignment.  Thus, your files for homework #3 will be in the directory home/cis15/homework/hw-3 (where home is your home directory  Put all C++ code, input and output files in that directory. Subdirectories can be created as needed.

18. Introduction to UNIX 18 Formatting Your Code Please use proper indentation-- reading code is like reading and essay-- improperly indented code is like text without punctuation, capitalization, and the other conventions of proper writing. You must develop the habit of proper indentation. Please give some thought to your identifier and function names-- single letters such as i or x are fine for loop/array indexes or symbols in a mathematical equation, but beyond that, the variables should be names reflecting the data/function they hold/perform. The first line of output from your program should contain your name, Unix id, course number and homework number. Each source file you submit should have a comment at the top containing the same information as above plus the name of the file. For example: /* Ira Rudowsky */ /* rudowsky */ /* CIS 15 EM6 Spring 07 */ /* Assignment hw-1 */ /* hw-1.cpp */

19. Introduction to UNIX 19 C++ IDEs One way to work on your assignments is to code and debug on your local machine using an IDE (Dec/C++ http://www.bloodshed.net/devcpp.html or Code::Blocks http://www.codeblocks.org are two possibilities) and then transfer you code to the Atrium servers. (SSH Secure File Transfer or Core FTP LE http://www.coreftp.com/download.html and selecting the SSH/SFTP option. http://www.bloodshed.net/devcpp.html http://www.codeblocks.org http://www.coreftp.com/download.html To edit files on the Unix server, two possible editors are vi or pico (shows you useful commands in the editor window). The Andersen book explains both or you can Google tutorials for either editor and find numerous sources of information online. The Unix compiler is invoked by the g++ command (see below for more).

20. Introduction to UNIX 20 UNIX at BC Most of the machines are running Solaris 9, the rest Solaris 8. The GUIs available are Sun's openwin, CDE and gnome. Both gcc and sun's compilers are available. Only the command line compilers are usually used. cc and CC are the front ends to Sun's C and C++ compilers. gcc and g++ are the front ends to gcc's C and C++ compilers.  cc -flags or CC -flags prints available compiler options Use an editor to write the code, save the file e.g., abc.c  g++ test1.cpp -o test1 produces file test1 if there are no errors Run the program by its name test1  The default output name is a.out is you omit the –o option.

21. Introduction to UNIX 21 UNIX at BC A lot of information regarding the Unix servers can be found at http://acc6.its.brooklyn.cuny.edu/AtriumSunGuide/Table_of_Contents.html http://acc6.its.brooklyn.cuny.edu/AtriumSunGuide/Table_of_Contents.html This includes  General Information General Information  Unix Commands Unix Commands  Korn Shell Korn Shell  Regular Expressions Regular Expressions  Floppies, Mtools Floppies, Mtools  Tar Tar  Editing Vi, Pico Editing Vi, Pico  Compilers, Debuggers Compilers, Debuggers  OpenWindows OpenWindows  Email, Pine, Talk Email, Pine, Talk  MailTool MailTool  Browsers Netscape, Lynx Browsers Netscape, Lynx  Gopher Gopher  NewsReaders Trn, Xrn NewsReaders Trn, Xrn  NcFtp NcFtp  Rules Rules