Set4: UNIX1

Title Slide

CSS 404/504

Internet Concepts

The UNIX Operating System (1)

By

Ralph B. Bisland, Jr.

2Internet Concepts Copyright Ralph Bisland 2004

The UNIX Operating System• Developed from the Multics Operating

System project• Developed at Bell Labs in 1969

(Originally called Unics)• UNIX commands are text based

(command interpreter)• Windows version of UNIX: X-Windows


Versions Of UNIX• Called shells

– C-Shell (csh) – TC Shell (tcsh) – Korn Shell (ksh) – Z shell (zsh) (what I use)– Borne Shell (bsh)– Borne Again Shell (bash) (USM CS

Default)


Why Learn UNIX

• Most Internet Service Providers (ISPs) utilize the UNIX Operating System

• Some ISPs use GUI interfaces - limit what you can do

• UNIX Operating systems have communications software built into their software.


UNIX Basics• UNIX commands are very cryptic (Often

2 letters)• The case of UNIX commands is very

important!!!!!!!!– ls LS Ls

• UNIX commands are usually entered in lowercase


Command Parameters• UNIX commands may have parameters

• Parameters are uused to specify options to commands

• Case is important here too• Parameters are preceded by a dash• Multiple parameters may be grouped together

or specified separately• Multiple parameters may be placed in any order

the user desires• Examples

– ls -a– ls -al– ls -la


UNIX Basics (ctd)• The UNIX prompt differs with each shell

• Z-Shell default prompt is: orca:~%– This may be altered

• UNIX is not MS-DOS, Windows, or Macintosh OS X

• Since MS-DOS "borrowed" some concepts from UNIX, some UNIX concepts are very similar to MS-DOS


Connecting to Orca• For security reasons this must be done

through secure shell (ssh) and not telnet.• To get a free ssh client program enter ssh

client (or ssh macintosh) into a search engine.• You also try Putty (win32 client)• Click on the Secure Shell icon to start it up.• Click on “Quick connect” to connect to orca.


Login Names & Passwords• To connect to a UNIX based computer

system two things are needed:– Login name (login ID)– Password


Login Names• General rules:

– 6-8 characters– digits– Can contain special characters such as -, _,

and .– Case sensitive

• This is assigned by the system administrator and can not be changed.

• This becomes your E-mail [email protected]


Passwords• General rules:

– At least 6 characters, at least 2 must be non-lowercase letters

• Passwords should be kept confidential.• Do not use simple names, dates, etc. as

passwords.• Use a sentence to create your password.• Example: I

am a Computer Science majorIaaCSm


Changing Passwords• To change your password, use the password

command (passwd)• Format: passwd NOTE: This will not work on the

ocean system• Example:orca% passwdEnter login (LDAP) password:New UNIX password:Retype new UNIX password:orca%

• Note that for security reasons the passwords are not echoed


Disconnecting from OrcaTo disconnect from orca, enter any of the

following commands: (well most probably)logout (This one works all the time)exitbyelo (works for me)

Remember that case is important when entering the commands!!!!

After doing this you also have to exit the ssh client.


UNIX Files• A file is a collection of data that is

stored on some secondary storage device.

• UNIX file names have no maximum storage limit.

• UNIX file are where the HTML commands for creating web pages are stored.


UNIX File Naming Conventions• Limited to 64 characters

• May contain special characters (except blank, / and possibly a leading -)

• Files that begin with a period (called a dot) have special meanings

• Case of letters is important. my-file MY-FILE My-File• Convention calls for a file extension to be appended

to each file name.• Place a period after the file name and add the

extensionmy-file.dat


UNIX Directories Directories/subdirectories are used to

segregate files On PC/Macs these are called folders The UNIX directory system forms a tree or

hierarchical structure The top directory of the tree is called the

root Each user has a home directory (which is a

subdirectory of root)• The user's home directory is the user's login

name


UNIX Directories

Root

Bisland Gregg Rimes

Not exact but close enough for now


Directory Notes• You may currently "reside" in only one

directory/subdirectory at a time.• Once you transfer from one directory to

another, you leave the first one and enter the second one.

• The directory/subdirectory that you currently reside in is called your "current working directory" (cwd) or "working directory“.


Orca’s Directory Structure• Orca’s directory system is configured its UNIX

directories as follows:/logical-computer-name/group-name/login-name

(slashes separate subdirectories)• Where

– logical-computer-name: Logical name of the computing systems

– group-name: Logical group name that the user falls into. Probably faculty, student, many others

– login-name: User's login name• Example:/orca/faculty/bisland


Orca’s Directory Structureorca

Faculty Students Staff others

Bisland Gregg

Internet Database SE-Eng

T-Hunts Tests


Creation Of Subdirectories• To create a subdirectory, use the make

directory (mkdir) command• Format: mkdir subdirectory-name• Example: orca% mkdir internet-course

• The command creates a subdirectory in your working current directory


Moving To Subdirectories• To make a subdirectory your current working

directory, use the change directory (cd) command.

• Format: cd subdirectory-name• Example:

orca% cd internet-course• Use the cd command by itself move back to

your home directory from any subdirectory.


Moving To Subdirectories (ctd)

• Every directory contains two files called . (dot) and .. (dot dot)– . => Name of the current working directory– .. => Name of the superdirectory of the current

working directory• To move back up one level, use the

command cd ..$ cd ..


Files In Other Directories• To access a file in another directory, you

must specify the path to the file• The path may be specified in either of two

ways:– Absolute Path: The exact path to the file

relative to the computer’s home directory– Relative Path: Relative to the current

working directory


Relative Path NamesLocation of a file relative to the current working directory.

bisland

internet

grades

database

projects

Assume that the cwd is internet, the relative path to the file test1.dat in thesubdirectory grades is

grades/test1.dat

Note that a slash does not precede the first subdirectory name


Absolute Path NamesLocation of the file regardless of the current working directory

bisland

internet

grades

database

projects

Assume the cwd is database and we wanted to get to the file test1.dat in the grades subdirectory, the absolute path name is:

/orca/faculty/bisland/internet/grades/test1.dat

Note that absolute directory names are preceded by a slash

Note that the absolute path name includes the logical computer name followedby the group name, followed by the logon name (the home directory), followedby the subdirectories


The Tilde Symbol• The tilde symbol (~) can be used to get to a user's home

directory• UNIX uses it's internal files to find the specified home

directory• To get to the test1.dat file in the previous example, we

could specify the path:

/orca/faculty/bisland/internet/grades/test1.dat

or using the tilde notation we could access it with the following path:

~bisland/internet/grades/test1.dat


Where Am I?• To display the absolute path to your current

working directory use the print working directory (pwd) command.

• Format: pwd

• Example:

orca% pwdorca/faculty/bisland/internet


Removing Directories• Subdirectories can only be removed when they

are empty! • The only files they contain are . and ..

(Removal of files is discussed later)• To remove a directory, the cwd must be the parent

directory• To remove a subdirectory, use the remove directory

command (rmdir)• Format: rmdir subdirectory-name• Example:

orca % rmdir internet


Displaying A Directory• To display the names of the files in a directory

use the list command (ls)• Format: ls [-parameters]• Example 1: (list the names of the files in the cwd)

orca% ls • Example 2: (lists the names of the files in the

subdirectory internet-course)

orca% ls internet-course


Displaying A Directory (ctd)• Parameters:

– a: All files with a directory (including ones that begin with a period)

– F: Directories are displayed with a slash suffix and programs are displayed with an asterisk suffix

– l: Produces a long listing of each directory entry• Example 3: (produces a long list of

everything in cwd)

orca % ls -l


Displaying The Contents Of A File• There are several utility programs to list

the contents of a file available in UNIX– Catenate (cat): – More (more)– Less (less)– Head (head)– Tail (tail)


Catenate• Lists the contents of a file from top to

bottom.• If the file is too long to fit on a page, the

excess is scrolled off the top of the page.

• Good for listing small files. • Format: cat filename

orca% cat my-file.dat


More• Displays the first "page" of the file and

waits for instructions– Return Key = One new line is displayed– Space Bar = One new page is displayed– q = Quit the display

• Format: more filename

orca% more my-file.dat


Head & Tail

• The head and tail commands are used to display parts of a text file.

• You may optionally specify the number of lines to list.

• Default is 10 lines• Formats: head [-l] <filename> tail [-|+l] <filename> orca% head my-file.dat

orca% tail my-file.dat

orca% head -20 my-file.dat

orca% tail -20 my-file.dat

orca% tail +10 my-file.dat {list from line 10 to EOF}


UNIX Text Editors

• Text Editor: A program that allows the creation and editing of text files.

• This is what we will use to create the HTML files.• Similar to a word processor but without all the

features• Text Editors create lines of text

– Each line is terminated by an EOLN mark– Each file is terminated by an EOF mark

• No fancy editing features like a word processor– Word wrap– Boldface, centering, underlining, etc.


PICO

• PICO = PIne COmposer• Very simple text editor - can only be used on

text files (ASCII files).• Limited in what it can do (find and replace,

delete multiple lines, etc.)• Default editor on the orca system.• Some of the PICO commands are shown

across the bottom of the screen.• All PICO commands begin with a control key

(shown as ^letter).


PICO (ctd)• To enter the PICO Editor, enter the word

"pico", followed by a blank space, followed by the name of the file you wish to create/edit.

• orca % pico my-file.dat• The screen will clear and the PICO edit

window is now open.• Use the arrow keys to move the cursor

around.• Whatever you enter will be entered in the

text file.


List Of The PICO Commands

^G: Help on PICO. (F1)

^F: Move the cursor forward one character.^B: Move the cursor backward one character.^N: Move the cursor down (next) one line.^P: Move the cursor up (previous) line.Â: Move the cursor to the beginning of the current line.Ê: Move the cursor to the end of the current line.^V: Move cursor forward a page. (F8)^Y: Move the cursor backward a page. (F7)

^W: Search for (where is) text neglecting case. (F6)^L: Refresh the display.

^D: Delete the character at the cursor^K: Delete (kill) the entire line at the current cursor position. (F9) Note: Consecutive deletes append lines to the buffer which subsequently undeletes will write at the current cursor position.

Û: Undelete the last line(s) deleted at the cursor. (F10)

Î: Insert a tab at the current cursor position.


List Of PICO Commands (ctd)^J: Format (justify) the current paragraph. (F4)

Note: Paragraphs delimited by blank lines or indentation

^T: Invoke the spelling checker. (F12)

^C: Report the current cursor position. (F11)

^R: Insert an external file at the current cursor position. (F5)

Ô: Output the current buffer to a file. (F3)

^X: Exit pico, saving the contents of the buffer to a file. (F2)


Sample PICO Edit Session PICO 1.7 File: my-file.dat

[ New file ]^G Get Help Ô WriteOut ^R Read File^Y Prev Pg ^K Del Line ^C Cur Pos^X Exit ^J Justify ^W Where is ^V Next Pg Û UnDel Lin^T To Spell


Deleting Files• To delete a file from the system, use the remove

command (rm)

• Format: rm filename

orca% rm my-file.dat

• You will probably be asked for confirmation when you remove a file.

orca% rm my-file.datrm: remove ‘my-file.dat’?


Wildcards

• In some file commands wild cards can be used to substitute for characters or character strings

Wildcard Meaning-------- --------------------------------------------- * Match any sequence of zero or more characters ? Match any single character [ ] Match one of the enclosed characters

• Note: The only character that can not be matched by a wildcard is the slash (/)


Wildcard Examplesorca% rm *.dat

orca% rm file*orca% rm ?.datorca% rm set[123].datorca% ls -l *.datorca% ls *.*orca% rm *


Renaming A File• To rename a file, use the move command (mv)

• Format: mv oldfile-name newfile-name• Example: orca% mv my-file.dat your-file.dat• Since a directory is in essence a file, directories

can be renamed via the mv command.• Format: mv old-directory-name new-directory-name orca% mv internet-course internet-stuff


Making A Duplicate Copy Of A File• To make a duplicate copy of a file, use the

copy command (cp)

• Format: cp old-file new-file

• Example:

orca% cp my-file.dat your-file.dat


Files In Different Directories• To move a file from one directory to another directory,

use the mv command• Format: mv <filename> <directory-name>• Example:

orca% mv my-file.dat internet-course

• To copy a file from one directory to another, use the cp command

• Format: cp <filename> <directory-name>

orca% cp my-file.dat internet-course


History• History allows you to retrieve previously entered

commands.• This only works on commands entered during the

current terminal session.• Once a command has been retrieved, it can be

executed and/or editted.• To retrieve previously entered commands use the

up arrow or the down arrow key.• To edit a command, use the backward or forward

key to position the cursor at the editing point, then enter character or delete characters.


Filename Completion• UNIX allows the user to enter enough character

of a filename to determine a unique file name, then completes the file name for you.

• To do this, enter enough characters for UNIX to identify the file name, then press the TAB key – UNIX completes the file name for you.

• This feature only works on file names, not commands.


Printing• Any text file may be printed on the laser

printer in JST 205 or TEC207• Caution: Only print text files on the

printer!!!• The command to print a text file is lpr.• Format: lpr <filename>• Example:

orca% lpr my-file.dat• To check on the status of the USM printers

use the lpstat command orca% lpstat

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Set4: UNIX1