UNIX ENVIRONMENT

DESIGNED BY :MITTINPREET SINGH NAYYARVIKAS K PRASAD

Introduction to Unix History of Unix Salient features of Unix SHELL Distributions Basic Unix Commands Q&A References

Roadmap

INTRODUCTION TO UNIX

A multi-tasking and multi-user Operating System Developed in 1969 at AT&T’s Bell Labs by

Ken Thompson (Unix) Dennis Ritchie (C) Peter Neumann suggested their project is given the name UNIX.

It is a portable operating system that is designed for both efficient multi-tasking and multi-user functions. Its portability allows it to run on different hardware platforms. It was written is C and lets user do processing and control under a shell.

Unix is case sensitive

HISTORY OF UNIX

The history of UNIX starts from the project MULTICS (Multiplexed Information and Computing Service) in 1965 conducted by AT&T,GE & MIT funded by DOD(Dept. of Defense)USA.

The main aim to develop UNIX was to develop and operating system that could serve large Community of users and allow them to share data if needed be. This never to be enterprise called MULTICS

In 1969, ken Thompson and Dennis Ritchie released the first version of Multiuser System Called UNIX. At that time Unix was not portable. To remedy this Ken Thompson created a new language “B” but language lacked some aspects. So in 1973 UNIX was Rewritten in “C” Language by Ken Thompson. C Language was developed by Dennis Ritchie.

SALIENT FEATURE OF UNIX

Multiuser Capability Multitasking Capability Communication Security Portability

What is SHELL

A shell acts as an interface between the user and the system. As a command interpreter, the shell takes commands that we give interpret the command and then conveys them to the kernel which ultimate executes them. You can imagine kernel as a monarch who is the overall control of everything where as the shell as its emissary

TYPES Of SHELLS BOURNE SHELL Steve Bourne Creation, known after him Bourne Shell is the most popular. It comes with every Unix System C SHELL This shell is a hit with those who are seriously into Unix programming, created by Bill Joy, it had two advantage over Bourne Shell. It allows aliasing of commands the other one is history feature. KORN SHELL it is not widely used but is a powerful and superset of Bourne shell, created by David Korn.OTHER SHELLS ZSHELL BASH SHELL

SHELL Prompt of Ubuntu

To open the terminal in Ubuntu use can use the shortcut : ctrl + Alt + T

DISTRIBUTIONS Linux

Minix FreeBSD OpenBSD NetBSD GNU Hurd Solaris SCO Unix

ConclusionThere are many free Unix like operating systems floating around out there and most if not all of them can be found quickly with a simple internet search. The OS's I have listed above are, in my opinion, the best. They are also all available to use for free unlike most of the others.

Ubuntu Distribution

BASIC COMMANDS

This command returns your username. Sounds useless, but isn't. You may need to find out who it is who forgot to log out somewhere, and make sure *you* have logged out.Example: whoami

whoami

Man - Manual

In unix online help has been available since the beginning. In order to access all the available help, you have to tell the shell where to look for online help pages. This information is specified using the MANPATH. A common setting is:MANPATH=/usr/man:/usr/share/manWhen you use the man command to request online help as follows, the man command searches every directory given in the MANPATH for an online help page corresponding to the topic you have requested.

$man whoIn this case it looks for the online help page corresponding to the who command

A snapshot of $man who

Passwd

To change the password of the user we use passwd command Which ever password we create Unix stores it in /etc/passwd file

but in encrypted format, the password basically stored it in the Shadow File which is located in /etc/shadow.

We can even cat this file on the screen lets you change your password, which you should do regularly (at

least once a year).$cat /etc/passwd

cal - Calender

Display a conveniently-formatted calendar from the command line.In general, if no options are given, cal displays the current month at the command line.

Touch

With this command we will learn how to create files With this we can create many files without storing anything in the

files. The size of the file is ZERO Bytes Q Why do we use touch ?A Not only does it creates empty files it also allows you to change the modification and access time of a file.we can even set the access time for a file to a particular time instead of current time.

Example: touch dinesh heena siddhi jatin

cat- concatenate

If we want to store a few lines in a file while creating it we use cat command. One’s you are through with typing content press the keys : Ctrl + d . In Unix Ctrl + d indicates the EOF(End of File)

To display the content of file under DOS we use type command. To see content of file we use the following command Umask 0022Example : cat >dheeraj - for creating filecat < dheeraj or cat dheeraj - will show you the output

cp- copyCopies Files from one Directory or location to another file or directory.Cp command takes the liberty to overwrite the file to the destination it will not even give a warning.

Example:$cp abc.c xyz.c mycfile.txt$cp abc.c xyz.c $cp /usr/aa16/chapter1 /usr/aa16/newbook/chap1

The last command when executed it will copy the chapter1 file to /usr/aa16/newbook. When copied to this directory it would have the name chap1 instead of chapter1

rm - removeThe rm command removes (deletes) files or directories. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. The removal process unlinks a filename in a filesystem from data on the storage device, and marks that space as usable by future writes. In other words, removing files increases the amount of available space on your disk.The data itself is not destroyed, but after being unlinked, it becomes inaccessible. Remove your files wisely! The effects of an rm operation cannot be undone.Note: If what you want is to completely, unrecoverable erase the data on the disk, use the shred command instead. This will overwrite the file's contents so that they cannot be reconstructed later by any means.

options of rm command:-i -> it is used for interactive deletion of files and directory-r-> it will recusively delete the items. It means if there is a sub directory

inside the directory-f-> it will forcibly remove the directory

Ls-list

ls --- lists your files ls -l --- lists your files in 'long format', which contains lots of useful information, e.g. the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified. ls -a --- lists all files, including the ones whose filenames begin in a dot, which you do not always want to see. There are many more options, for example to list files by size, by date, recursively etc.

mv - move or rename

moves a file (i.e. gives it a different name, or moves it into a different directory

mkdir – make directory

Create the DIRECTORY(ies), if they do not already exist. Mandatory arguments to long options are mandatory for short options too. -m, --mode=MODE

set permission mode (as in chmod), not rwxrwxrwx - umask -p, --parents

no error if existing, make parent directories as needed -v, --verbose

print a message for each created directory

cd – change directory

change directory. You basically 'go' to another directory, and you will see the files in that directory when you do 'ls'. You always start out in your 'home directory', and you can get back there by typing 'cd' without arguments. 'cd ..' will get you one level up from your current position. You don't have to walk along step by step - you can make big leaps or avoid walking around by specifying pathnames.

Example: $cd eleven

Pwd- print working directory

pwd prints the full pathname of the current working directory.

logname

Logname prints the user login name who is logged in . Print the name of the current user. Example: logname

uname

Print certain system information. If no OPTION is specified, uname assumes the -s option.

Example: Uname –a

who

The who command prints information about all users who are currently logged in.

sort

sort is a simple and very useful command which will rearrange the lines in a text file so that they are sorted, numerically and alphabetically. By default, the rules for sorting are: lines starting with a number will appear before lines starting with a

letter; lines starting with a letter that appears earlier in the alphabet will

appear before lines starting with a letter that appears later in the alphabet;

lines starting with a lowercase letter will appear before lines starting with the same letter in uppercase.

tty – teletype terminals

tty - print the file name of the terminal connected to standard input In unix terminology, a tty is a particular kind of device file which

implements a number of additional commands (ioctls) beyond read and write. In its most common meaning, terminal is synonymous with tty. Some ttys are provided by the kernel on behalf of a hardware device, for example with the input coming from the keyboard and the output going to a text mode screen, or with the input and output transmitted over a serial line. Other ttys, sometimes called pseudo-ttys, are provided (through a thin kernel layer) by programs called terminal emulators, such as Xterm (running in the X Window System), Screen (which provides a layer of isolation between a program and another terminal), Ssh (which connects a terminal on one machine with programs on another machine), Expect (for scripting terminal interactions), etc.

ulimit

The ulimit programs allow to limit system-wide resource use. This can help a lot in system administration, e.g. when a user starts too many processes and therefore makes the system unresponsive for other users.

NOTE : Do not run this in a shell! If no limits are set your system will either become unresponsive or might even crash.

wc

wc, or "word count," prints a count of newlines, words, and bytes for each input file.

wc prints newline, word, and byte counts for each FILE, and a total if more than one FILE is specified. With no FILE, or when FILE is a dash ("-"), wc operates on standard input. (A word is a non-zero-length sequence of characters delimited by white space.)

Example: wc -l : Prints the number of lines in a file. wc -w : prints the number of words in a file. wc -c : Displays the count of bytes in a file. wc -m : prints the count of characters from a file. wc -L : prints only the length of the longest line in a file.

Head

head, by default, prints the first 10 lines of each FILE to standard output. With more than one FILE, it precedes each set of output with a header identifying the file name. If no FILE is specified, or when FILE is specified as a dash ("-"), head reads from standard input.

tail

Print the last 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. tail prints the last 10 lines of each FILE to standard output. With more than one FILE, it precedes each set of output with a header giving the file name. If no FILE is specified, or if FILE is specified as a dash ("-"), tail reads from standard input.

more

shows the first part of a file, just as much as will fit on one screen. Just hit the space bar to see more or q to quit. You can use /pattern to search for a pattern.

less

Less is a program similar to more (1), but which allows backward movement in the file as well as forward movement. Also, less does not have to read the entire input file before starting, so with large input files it starts up faster than text editors like vi (1). Less uses term cap (or term info on some systems), so it can run on a variety of terminals. There is even limited support for hardcopy terminals. (On a hardcopy terminal, lines which should be printed at the top of the screen are prefixed with a caret.)

date

Shows the current date and time.

chmod - change mode as permission

lets you change the read, write, and execute permissions on your files. The default is that only you can look at them and change them, but you may sometimes want to change these permissions. For example, chmod o+r filename will make the file readable for everyone, and chmod o-r filename will make it unreadable for others again. Note that for someone to be able to actually look at the file the directories it is in need to be at least executable. See help protection for more details.

References

Unix Shell Programming By Yashavant Kanetkar. Unix Concept and Application by Sumitabha Das. http://www.tutorialspoint.com/unix https://

www.youtube.com/watch?v=nVt3Rst-2H8&list=PL7B7FA4E693D8E790

Q&A SESSION

Thank you for your Patience