Unix Notes Fall 2002 Week 2 I Unix History 1960 s AT T developed MULTICS a multi user operating system 1969 AT T Bell Labs Unix system starts Ken Thompson supported by Rudd Canaday Doug McIlroy Joe Ossana and Dennis Ritchie wrote a small general purpose time sharing system which started to attract attention PDP 7 1970 Assembler based Unix system ported to PDP 11 1972 Dennis Ritchie develops the C language 1973 4th edition of Unix the kernel and shell are rewritten in C Group created at Bell Labs for internal support 25 systems First unofficial distribution to universities 1974 5th edition officially available to universities for educational purposes only AT T provides no support no trial period no warranty no bug fixes and customer MUST pay in advance Thus in the mid 1970 s the Unix system was licensed to universities and gained a wide popularity in the academic community because It was small early systems used a 512K byte disk It was flexible The source was available written in a high level language which promoted portability of the OS It was cheap Universities were able to receive a Unix system license for the price of a tape Disadvantages at the time It had no support AT T had spent resources on MULTICS and wasn t interested in pursuing the Unix OS It was buggy No support no fixes It had little or no documentation but you did get the source code 1975 Thompson attends University of California at Berkeley on sabbatical Berkeley development starts Supported by DARPA the developers could add a lot more features BSD Unix 1977 500 systems mostly at universities 1 BSD developed on PDP 11 First ports to non DEC equipment 1980 4 0 BSD caught the eye of DARPA who was looking for a non proprietary OS standard for networked research systems for CAD CAM AI and vision applications Berkeley s virtual memory development more advanced that AT T s 1983 System V Release 1 AT T announces official support The AT T Unix has added many features of BSD Unix 1984 Consent decree lifted Bell divestiture allows AT T to compete in the computer business 1987 750 000 Unix systems 1988 Open Software Foundation founded an independent company formed to develop and provide a computing environment that is based on industry standards and the best technologies that are available Today Unix is one of the front runners in the OS race POSIX Portable OS Interface for computer environments trying to combine the best features of System V Unix and BSD Unix into a standard There is NO standard so Each Unix is tailored by the manufacturer to better run on it s hardware so each individual flavor ULTRIX SCO Unix Lynex HPUnix although the basic command line interface is consistent throughout II Unix Introduction Unix as an OS has some decided advantages and disadvantages Advantages time sharing OS can support multiple users running multiple tasks Sharing resources between these users interactive flexible operating interface users can run multiple processes concurrently and switch between them support multiple users to facilitate the sharing of data between project member When installing Unix you only need to install the pieces relevant to your needs Provides security features that allow individual users to determine how their files are shared with others Disadvantages Interface can be difficult for a novice user to understand III There are 2 pieces to the Unix os Kernel and the Shell The Kernel is the operating system ultimately executes commands it is responsible for managing the available resources and access to the hardware Contains modules for each hardware component that it interfaces with As new types of hardware are installed on the system new modules can be incorporated into the kernel The shell s is an interactive command interpreter Commands are entered at the shell prompt and acted upon as they are issued Users communicate with the computer through the shell The shell is NOT the kernel it translates commands into a form the OS can understand and ships them to the kernel for execution Commands can be either implemented as part of the shell itself or stored as system programs Many different shells Examples of shells Bourne Shell sh original shell on AT T based Unix C shell csh shell developed at University of California Berkeley Provided on BSD machines syntax of shell scripts is similar to C A derivative of csh is tcsh or T shell Korn Shell derivative of the Bourne shell sh it is designed as an improvement featuring commands from both sh csh IV Unix Commands Some general interface issues In its basic form UNIX is a line oriented system similar to MS DOS or VMS Each command is terminated by the return or enter key UNIX uses the ASCII character set and supports upper and lower case In other words UNIX is case sensitive UNIX does not support function keys However most shells allow special functions to be invoked by using the control key IE An executing command can be terminated by pressing CTRL C or c What control keys are available vary from shell to shell Some features in UNIX editors take advantage of features of specific types of terminals delete key arrows Some times when you log on your screen may be jumbled you may not be able to use the arrow keys or if you open a file in an editor it may not display scroll properly If this happens you may need to specify your terminal type at the beginning of your session For remote access usually use DEC vt100 Setenv TERM vt100 Accessing our Unix server The easiest method for accessing the departmental server is via the web entering the URL boole csee wvu edu Logging on to an account The first part of accessing UNIX is to of course log on login password When you fill out an account application the system administrator will assign you a login userid and default password Standard Rules for passwords 8 characters at most should be a mixture of upper and lower case at least 1 character should be non alphabetic Once you login you will see a shell prompt The prompt simply indicates that the SHELL is ready to receive your next command is the default prompt for the Bourne shell sh A is the default prompt for the C shell csh is the reserved prompt for the root Prompts can be changed In UNIX a shell is a command just like every other UNIX command When you log on you automatically launch a shell program and since it acts as the command interpreter translating commands into a format the operating system can understand without a shell you would not be able to do much Most users