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USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering INTERNAL ASSESSMENT TEST – 1 Date : 23.2.2016 Subject & Code : UNIX and Shell Programming(10CS44) Name of Faculty : Prof. Ajoy Kumar Max Marks : 50 Section : A,B,C(CSE/ISE) Time : 11:30-1:00 PM Note: All Questions are compulsory 1. a With a neat diagram, explain the architecture of UNIX Operating System Solution: [3 Divisions 2 M each Diagram 1M] Ans: The unix architecture mainly consists of of 3 divisions: Division of labor:Kernel and Shell Division of labor between two agencies the kernel and shell.The kernel interacts with the machine's hardware, and the shell with the user.The kernel is core of operating system-a collection of routines mostly written in C.It is loaded into memory when the system is booted and communicates directly with the hardwarte.User programs-To use the hardware through a set of functions called the system calls.Kernel manages the system's memory,schedules processes,decides their priorities and performs other tasks.This is called the operating system-a program's gateway to the computer's resources.Command interpreter is actually the interface between the user and kernel. B.E IV Semester 7 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering Kernel-Shell relationship diagram The file and process Two simple entities support the Unix system-the file and process where files have places and processes have life.A file is just an array of bytes and can contain virtually anything.It contains directories and dominant file type is text.The secondary entity is the process,which is the name given to a file when it is executed as a program.Processes have parents,chidren and grandchildren,and are born and die. The system calls These are handful of functions used to communicate with the kernel.All UNIX flavours use the same system calls.These system calls are built into the kernel,and interaction through them represents an efficient means of communication with the system. B.E IV Semester USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering b Explain the following commands with example 2 i) gzip: used to compress the files.It provides extension .gz to the compressed file 1M options:gzip –d Uncompressing a file gzip –r Recursive compression example: gzip abc.html gzip –d abc.html ii)tar: Used to create disk archive that contains a group of files or an entire directory structure 1M options: -C: Create an archive -X: Extract files from archive -t: Display files in archive -f arch :Specify the archive arch c Create a file A.txt that contains 5 student details. Copy first 3 student details to another file B.txt and delete A.txt file Solution: Cat A.txt 01|ABC1 02|ABC2 03|ABC3 04|ABC4 05|ABC5 $ rm A.txt B.E IV Semester 1 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering 2. a Explain briefly absolute path name and relative path name with examples. Solution: Absolute pathname: (2.5 marks) If the first character of the pathname is /,the file's location must be determined with respect to root(the first /).Such a pathname is called as absolute pathname.(Eg:/home/kumar/login.sql).When we have more than one / in a pathname,for each such /,you have to descend one level in the file system.No two files in a UNIX system can have identical absolute pathnames. Using absolute pathname for a command: Eg; $ /bin/date Relative pathname: (2.5 marks) If the first character of the pathname is not /,.Such a pathname is called as relative pathname.Relative pathnamkes can be distinguished using . and . . in the pathname. . (a single dot) --This represents the current directory . . (two dots) – This represents the parent directory cd .. ---Moves one level up cd../.. ---Moves two levels up cd.. A filename can begin with a dot cp ../sharma/.profile B.E IV Semester 5 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering b Explain with diagram 3 different modes in which Vi editor works 5 Diagram 2M each mode 1M vi editor mainly consists of 3 modes: 3. a Command mode:The default mode of the editor where every key pressed is interpreted as a command to run on text.This mode is used to copy and delete the text. Input mode:Every key pressed after switching to this mode actually shows up as text.This mode is invoked by pressing any one of the following keys:(i,a,IA,o,O,R,S,s,rch) ex mode(Last Line mode):This mode is used to handle the files and perform substitution. Pressing a : in the command mode invokes this mode.This is carried out by pressing any one of the following keys:-(:w,:x,:wq,:q) Explain standard input, standard output and standard error with respect to UNIX 4 Operating System Solution: The shell associates three files with the terminal-two for the display and one for the keyboard. These special files are actually streams of characters which many commands see as input and output. A stream is simply a sequence of bytes. Each stream is associated with a default device, and generically this device is a terminal. Standard Input Standard Output Standard error B.E IV Semester USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering b What are wild cards? Explain shells wild cards with example 6 Solution: The metacharacters that are used to construct the generalized pattern for matching filenames belong to a category called wild cards. This pattern is framed with ordinary characters and a metacharacter using well defined rules. The pattern can then be used as an argument to the command, and the shell will expand it suitably before the command is executed. Explanation of the following wild cards with examples. * ? [ijk] [x-z] [!ijk] [!x-z] B.E IV Semester USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering 4. a A file’s current permissions are rw_r_xr_ _.Specify the chmod expression required to change them for the following i) rwx rwx rwx ii) r_ _r_ _r_ _ _ iii) _ _ _r_ _r_ _ iv) _ _ _ _ _ _ _ _ _(1.5marks each) using both the relative and absolute methods Solution: i) rwx rwx rwx Using Relative $chmod ug0+rwx file Or $chmod u+x file $chmod g+w file $chmod o+wx file Using Absolute $chmod 777 file ii) r_ _r_ _r_ _ _ Using relative $chmod u-w file $chmod g-x file Using absolute $chmod 444 file iii) _ _ _r_ _r_ _ Using relative $chmod u-rx file $chmod g-x file Using absolute $chmod 044 file iv) _________ Using relative $chmod u-rw file $chmod g-rx file $chmod o-r file Using absolute $chmod 000 file B.E IV Semester 6 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering b Explain briefly file attributes listed using ls - l command Solution: File attributes of ls-l 5. a File type and permissions Links Ownership Group ownership File size Last modification time File name Explain the following commands with example i) Comm: This command is used to display differencing and common entries in two files (1M) ii) iii) diff : This command can be used to list the differences between the two files It also lists which lines in one file need to be changed to make both the files similar (1M) passwd : This command is used to change the password Example: $ passwd (2M) iv) stty: This command is used to change and display the settings of the terminal Example: $stty -a ,displays the current settings stty – echo, turns off keyboard input (2M) v) who : This command is used to display all the users(2M) options: -Hu : to provide more details $ who am I : is used to know the user who invoked the command vi) tee : tee is an external command and not a feature of shell. It handles a character stream by duplicating its input. It saves one copy in a file and writes the other to standard output. (2M) B.E IV Semester 4 10 USN 1 P E PESIT Bangalore South Campus Hosur road, 1km before Electronic City, Bengaluru -100 Department of Computer Science And Engineering ******** B.E IV Semester