Introduction to Unix: Fundamental Commands

1 Başar Öztayşi 2011

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Introduction to Unix:Fundamental Commands


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What You Will Learn

• The fundamental commands of the Unix operating system.

• Everything told for Unix here is applicable to the Linux operating system also.


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What is Unix

• UNIX is a computer operating system, a control program that works with users to –run programs, –manage resources, and –communicate with other computer systems.

• Several people can use a UNIX computer at the same time; hence UNIX is called a multi user system. Any of these users can also run multiple programs at the same time; hence UNIX is called multitasking.


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Logging on to a UNIX machine

• Because UNIX is a multi user operating system, you need to start by finding a terminal, computer, or other way to access the system.

• Connect your terminal or PC to the UNIX system until the point where you see a login prompt(login:) on your screen. Use the phone and modem to dial up the computer if you need to.


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Connecting a PC (MS-Windows) to Unix System

• The machine that we are going to connect is called hyperion.labs.itu.edu.tr

• Select Start → Run and type SshClient in the empty box

• This will start the SSH program


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• Choose Quick Connect, a new window will come up to the screen

• In the HostName section, type ssh.itu.edu.tr

• In the UserName section, enter your login name

• Leave other parts as their default values.


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• When you press Connectbutton, you will see a password prompt.

• Enter your password exactly and press OK button.

• Your login name and password are case-sensitive.


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• You are now logged into the computer and will have a prompt that reflects the computer's name. For example, if you connect to hyperion machine, the prompt looks like this:

[oztaysib@ssh ~]$ • Once you’ve successfully entered your account name and

password, you are shown some information about the system, some news for users, and an indication of whether you have electronic mail. The specifics will vary.

• At this point, you’re ready to enter your first UNIX command.


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Shell Commands of UNIX

• Unix Commands• When you first log into a unix system, you are

presented with something that looks like the following:[oztaysib@ssh ~]

• That “something” is called a prompt. As its name would suggest, it is prompting you to enter a command.

• Every unix command is a sequence of letters, numbers and characters. But there are no spaces.


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• Unix is also case-sensitive. This means that cat and Cat are different commands.

• The prompt is displayed by a special program called the shell.

• Shells accept commands, and run those commands. • They can also be programmed in their own language.

These programs are called “shellscripts”.


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• There are two major types of shells in unix:– Bourne shells– C shells.

• Steven Bourne wrote the original unix shell sh, and most shells since then end in the letters sh to indicate they are extentionson the original idea

• Linux comes with a Bourne shell called bash written by the Free Software Foundation.

• bash stands for Bourne Again Shell and is the default shell to use running linux


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• When you first login, the prompt is displayed by bash, and you are running your first unix program, the bash shell.

• As long as you are logged in, the bash shell will constantly be running.


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Storing information

• Unix provides files and directories.• A directory is like a folder: it contains pieces of paper, or

files. • A large folder can even hold other folders-directories can

be inside directories.• In unix, the collection of directories and files is called the

file system. Initially, the file system consists of one directory, called the “root” directory

• Inside “root” directory, there are more directories, and inside those directories are files and yet more directories.


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• Each file and each directory has a name.• A short name for a file could be joe, • while it’s “full name” would be /home/larry/joe. The full

name is usually called the path.• The path can be divide into a sequence of directories. • For example, here is how /home/larry/joe is read:


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• A path could refer to either a directory or a filename, so joe could be either.

• All the items before the short name must be directories.


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• To see linux commands press Tab key,• If you want to learn commands beginning with

c you can write c then press Tab key /home/larry# c


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Obtaining help

• The man command displays reference pages for the command you specify.

• The UNIX man pages (man is short for manual) cover every command available.

• To search for a man page, enter man followed by the name of the command to find .

[oztaysib@ssh ~]$ man ls

(press q to exit)


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Obtaining Help

• To Exit press q


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man ((obtaining help))

• There is also a keyword function in man.• For example; –If you are interested in any commands that deal

with Postscript, the printer control language for Adobe • Type man -k ps or man -k Postscript,• you’ll get a listing of all commands, system calls, and other

documented parts of unix that have the word “ps” (or “Postscript”) in their name or short description.

• This can be very useful when you’re looking for a tool to do something, but you don’t know it’s name-or if it even exists!


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LAB. EXTENSİON


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Application 3

• A. ls: “list directory contents”– ls –al: “Show all and long listing”– ls -F: Adds a slash after the name for directories, an asterisk

for executables, and an at sign (@) for linked files.• B. man: displays online manual pages• C. mkdir BIL101E: Creat a directory named BIL101E• D. cd BIL101E: change directory to BIL101E• E. touch: change file timestamps

– touch deneme.txt: creates the file if does not exist


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Application 3

• F. mkdir GECICI: Creat a directory named GECICI• G. cd GECICI: change directory to BIL101E• H. ls: list the directory content• I. cd ..: change directory to mother directory• J. cp deneme.txt GECICI: copy deneme.txt to GECICI directory• K. mv Deneme.txt GECICI: move Deneme.txt to GECICI

directory• L. mv deneme.exe GECICI• M. ls GECICI• N. : rm remove deneme.txt in the GECICI directory


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Application 3

• O. cd GECICI: go to GECICI directory• P. rm Deneme.txt: remove the file in GECICI 8without declaring

the directory)• Q. mkdir YOK: create a new directory with the name YOK• R. rmdir YOK: remove the directory named YOK• S. cd .. :Change directory


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EDITORS: joe-pico-vi

• A4. pico myfile.txt [create file named myfile.txt]– Bu benim ilke editör kullanısım– (CTRL+ X) [close the file]

• A5. cat myfile.txt [displays the contents of a file.]• A6. vi myfile.c

– i– // Bu benim ikinci editor kullanısım– Shift-ZZ– cat myfile.c

• A7. gcc myfile.c – o myfile.exe compile the code and create the exe file


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-trees – chmod-• A8. tree :list the content of directories in a tree-like format• A9. ls –la : show all and long listing • A10. permissions | filecount | user | group | size | date | filename with extension• -r-x-x-x 1 aribas user 102 23 May 1996 myfile.c

• Position 1 file type: d (directory) - (ordinary file) l (symbolic link) • Position 2-4 permissions for the owner: r (read), w (write) , x (execute)• Position 5-7 permissions for other users in the same group• Position 8-10 permissions for all other users • Read: 4 Write: 2 Execute : 1• A11. chmod 700 myfile.txt : all rights to the owner• A12. ls –la: show all and long listing • A13. chmod 744 myfile.txt: all rights to the owner, only read to others• A14. chmod 711 myfile.exe: all rights to the owner, only exec to others


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-trees – chmod-

• A15. grep ‘Bu' myfile.c : searches the given file for lines containing a match to the given strings or words

• A16. wc –l myfile.c : displays a count of lines in a file. wc –w myfile.c : displays a count of words in a file.

• A17. spell myfile.c : Looks through a text file and reports any words that it finds in the text file that are not in the dictionary.

• A18. cmp myfile.c myfile.txt: The cmp utility compares two files of any type and writes the byte and line number at which the first difference occurred is reported.

• A19. diff myfile.c myfile.txt : find the differences between two files


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• A20. tr a b translate specified characters into other characters or to delete them.

• A21. gzip compress or expand files • A22. tar xvf panda.tar Extract files from panda.tar.• A23.?• A24. ls i?u• A25. ls –F > mylist.txt• A26. !1 – pine / email• A27. !2


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Network – storage- system tools

• A28. ps –aux : displays information about a selection of the active processes

• A29. du –kh : Summarize disk usage of each FILE in mb• A30. df : Report how much free disk space is available• A31. who: show who is logged on• A32. uptime: tell how long the system has been running• A33. whoami: user name associated with the current

effective user ID• A34. where: • A35. w: Show who is logged on and what they are doing• A.36. pid: Retrieve process id


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Network – storage- system tools

• A37. kill % terminate a process • A38. kill -9 terminate a process based on Process ID• A39. fg : Continues a stopped job by running it in the

foreground,• A40. bg: Continues a stopped job in the background• A41. ssh hyperion.labs.itu.edu.tr :OpenSSH SSH client

(remote login program) • A42. finger : user information lookup program


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• A43. bash : Bash is an sh-compatible command language interpreter that executes commands read from the standard input or from a file.

• A44. tcsh: It is a command language interpreter usable both as an interactive login shell and a shell script command processor.

• A45. sh: command language interpreter that executes commands read from the standard input or from a file

• A.46. cat .profile• A.47 cat bash.rc

– EKLER ; tail ; head ; scp

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Introduction to Unix: Fundamental Commands

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