1 the unix file system by chokechai chuensukanant id 121779 cosc 513 operating system
TRANSCRIPT
1
THE UNIX FILE SYSTEM
By
Chokechai Chuensukanant
ID 121779
COSC 513 Operating System
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Why you should know UNIX
- FREE ! FREE ! FREE !!!!!!
- Source code is openly available
- Linux, its background in UNIX, will soon have a lead position in the mid to high-end server market
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The UNIX File System
• DISK ORGANIZATION
- UNIX allows you to divide your hard disk into many units (called directories), sub units (called subdirectories)
- UNIX provides commands to create, organize, and keep track of directories and files on the disk.
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FILE TYPES UNDER UNIX
• Regular files - Contain sequences of bytes that could be programming code, data, text, and so on.
• Directories files- Contain information (like the file name) about other files. It consists of a number of such records in special format defined by your operating system.
• Special Files (device files)
- Contain specific information corresponding to peripheral devices such as printers, disk, and so on. UNIX treats I/O devices as files, and each de
vice in your system.
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ABOUT DIRECTORY
• The directory structure is organized in levels and is known as a hierarchical structure.
• The highest level is called the ‘root’.
• Do not contain the information but instead provide a reference path to allow you to organize your files.
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ABOUT DIRECTORY
• Directory Structure
binbin liblib usrusr devdev
rootroot
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Important Directories
• /usr : holds users’ home directories. Similarly to /home in Linux
• /bin : holds many of the basic UNIX program files. holds many of the basic UNIX program files. bin stands for binary, and these files are executable files.
• /dev : holds device files.
• /etc : holds many of UNIX configuration files.
• /sbin : holds system files that usually are run automatically by UNIX system.
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Path and Pathnames
• Every file has a pathname.
• The pathname locates the file in the file system.
• 2 types
- Absolute Pathname
- Relative Pathname
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Path and Pathnames
/// (root pathname)
binbin liblib usrusr devdev
/usr (usr pathname)Root Subdirectories
daviddavid danieldaniel gabrielgabriel
user subdirectories
/usr/david pathname)
myfirst
myfirst
reportreport
/usr/david/myfirst (myfirst pathname)
/usr/david/report (report pathname)
Pathnames in a Directory Structure
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Absolute Pathname
• Traces a path from the root to the file.
• Using when you want to access file that is not in your current directory.
• Always use the forward slash (/) at the beginning of the pathname for the root directory.
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Relative Pathname
• Traces a path from current directory to the file.
• Using when you want to access file that is in your subdirectories of your current directory.
• There is no initial forward slash (/)
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Using File and Directory Name
• The maximum length depend on the UNIX version, up to 255 characters.
• Avoid to use <>,(),[],{},*,?,”,’,-,$,^
• Can’t use spaces ( ), in files name
• Using more than one dot is allowed in UNIX
• Case sensitive
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Directory Command
• Displaying a Directory pathname: The pwd (print working directory) command.
• Changing your Working Directory: The cd command
• Creating Directories The mkdir Command
• Removing Directories: The rmdir Command
• Listing Directories: The ls Command
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The pwd command
• Display the absolute pathname of your working directory.
• Similarly to chdir command in DOS
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The cd command
• Change your current directory
• cd $HOME using when want to return your directory.
• Similarly to cd command in DOS
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The mkdir Command
• Create new subdirectory under your working directory
• Similarly to md or mkdir command in DOS• Using option –p to create level directories in si
ngle command
Example mkdir –p /level1/level2/level3 means create directory level1 in current directory and create directory level2 in level1 directory and create level3 in level2 directory
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The rmdir Command
• Remove existing directory
• Must be in the parent directory to remove subdirectory.
• Must remove only empty directory.
• Similarly to rd or rmdir command in DOS
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The ls Command
• List subdirectories and files in current directory.
• Can use multiple options in single line
• Similarly to dir command in DOS
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Display File Contents:
• Using the cat Command
- To display file contents.
- Usually use with small files.
- Similarly to type command in DOS.
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Printing File Contents
• The lp command
- To send a copy of a file to the printer for producing a hard copy of the file.
- Can specify several files on one command line .
- Similarly to print command in DOS.
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Printing File Contents
• The cancel command
- To cancel request for print jobs made with the lp command.
• The lpstat command
- To obtain information about printing requests and the status on the printers.
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FILE MANIPULATION COMMANDS
Copying Files: The cp CommandMoving Files: The mv CommandLinking Files: The ln CommandDeleting files : The rm command
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The cp Command
• Used to create a copy (duplicate) of a file.
• Syntax
$ cp [option] [Source] [Destination]
• Source and Destination could be file or directory.
• Could have more than one source on single line but Destination must be directory.
• Similarly to copy command in DOS
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The mv Command
• Used to move a file from one place to another or to change the name of a file or directory
• Syntax
$ mv [option] [Source] [Destination]
• Source and Destination could be file or directory.
• Could have more than one source on single line but Destination must be directory.
• Similarly to move command in DOS
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The ln Command
• To create new links (name) between an existing file and a new filename.
• In the other word, create additional names for an existing file
• Syntax
$ ln [option] [existing file name] [new name]
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The rm command
• UNIX does not give you any warning message, so think twice before using this command.
• Syntax
$ rm [Existing file names] • Similarly to del command in DOS.
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Summary
• This presentation just show you a few basic command in UNIX.
• In more advance, I have summary more command and keep them at
http://www10.brinkster.com/boyb1917/unix.htm
• If you want to know more about UNIX , please check that out or register UNIX class on next quadmester and I will see you there.
• GOOD LUCK !!!!!!!!!!