Directory Commands

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Chapter 4

• Directory Commands

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Overview

• The disk partitioning scheme will be explained
• Will learn to manage files in the GUI (using the
  Nautilus file manager) and from the command line

3
Overview

• Will learn how to create, change, rename, and
  eliminate directories
• Will learn how to navigate in the directory
  structure using cd and dat addressing techniques

4
Overview

• The power of and danger of removing directories
  recursively will be discussed
• Will view and manipulate environmental variables

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Hierarchical Filing System or Tree-structured
Directories

• Directories and subdirectories are the means of
  locating and logically grouping files

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Hierarchical Filing System or Tree-structured
Directories

• The hard disks major purpose is to store and
  retrieve data

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Hierarchical Filing System or Tree-structured
Directories

• A disk is divided into partitions
• Each partition
• accessed as if it were a separate disk
• must have a file system installed on it

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Hierarchical Filing System or Tree-structured
Directories Figure 4.1 Total Disk Space p. 177
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Hierarchical Filing System or Tree-structured
Directories

• Partition table states
• Where partition begins and ends
• Whether partition is/is not active
• Partition type

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Hierarchical Filing System or Tree-structured
DirectoriesFigure 4.2 Typical Computer with
Windows p. 177
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Hierarchical Filing System or Tree-structured
Directories Figure 4.3 Dual Booting System p.
178
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Hierarchical Filing System or Tree-structured
DirectoriesTable 4.1 Linux Partition-naming
Scheme p. 178
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Hierarchical Filing System or Tree-structured
Directories

• Each physical disk divided into a maximum of
  four primary partitions
• One partition type may be set to be extended
  (extended partition)

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Hierarchical Filing System or Tree-structured
DirectoriesFig 4.4 Windows Linux Using
Extended Partition p. 179
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Hierarchical Filing System or Tree-structured
Directories

• In Linux
• Partitions identified by device names
• Peripheral devices are also named

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Hierarchical Filing System or Tree-structured
Directories

• Each partition forms part of storage necessary to
  support a single set of files and directories

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Hierarchical Filing System or Tree-structured
Directories

• Associate partition with a directory through
  mounting
• Mount partition, make files and directories
  available starting at mount point

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Hierarchical Filing System or Tree-structured
Directories

• Linux provides a single hierarchy for all
  directories that includes every mounted partition
  and mounted peripheral device

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Hierarchical Filing System or Tree-structured
DirectoriesFigure 4.5 A Directory is Like a
Family Tree p. 180
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Hierarchical Filing System or Tree-structured
DirectoriesFigure 4.6 Hierarchical Structure of
a Directory p. 180
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Hierarchical Filing System or Tree-structured
DirectoriesFigure 4.7 Directories as Rooms p. 181
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Hierarchical Filing System or Tree-structured
DirectoriesFigure 4.8 Files in Subdirectories p.
182
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Managing Files and Directories

• Organization and structure of a disk is dependent
  on the file system used by the operating system

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Viewing Files and Directories

• Can view files/directories in various sequences

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Activity Viewing Files and Directories

• KEY CONCEPTS
• Can sort files using Nautilus or command line
• Files sorted by name, size, type., modification
  date, emblem, ascending/descending order
• typenot sorting by extension but by Type of
  name given to file
• -X used by ls to sort in file extension order
• Can combine two options
• -r is reverse order
• Defined terms emblem and links

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Creating Directories

• Subdirectory
• Setting up storage area for files
• Need write permission in parent directory
• Can be created using
• Nautilus File Manager
• mkdir command at command line
• Syntax mkdir options directoryname

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Creating DirectoriesTable 4.2 mkdir Options p.
188
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Activity How to Create Directories

• KEY CONCEPTS
• Nautilus is GUI file manager
• Typing replaces selection
• File menuwhere new folder created
• Uppercase letters come before lowercase
• Linux retains case chosen
• Can create directory from terminal window
• Can identify directories

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Activity How to Create Directories

• KEY CONCEPTS
• ls command
• displays contents (directories) of disk
• Directories are in a different color
• Syntaxls OPTIONFILE
• On same line separate commands with a semicolon
• Every directory (except root always has two
  names directories (dot and double dot)

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The Current Directory

• The current/default directory
• Is kept track of by the operating system
• Can be changed

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The Current Directory

• Purpose of the cd command
• Return to home directory
• cd with no parameters
• Change default directory
• Syntax is cd dir

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Activity Changing Directories

• KEY CONCEPTS
• Determined which directory was the
  current/default directory
• Prompt displays current directorynot the entire
  path name
• When a command is used it always assumes the
  default directory unless another drive and/or
  subdirectory is specified

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Building a Structure

• Create additional subdirectories using
• Nautilus File Manager
• mkdir command in terminal window
• Directory structure built from top down

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Building a Structure

• mkdir command
• Allows creation of structure with a single
  command
• -p option used to create parent directories
• Syntax mkdir optionsdirectory

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Building a Structure

• Absolute path
• Complete hierarchical structure
• Always correct
• Relative path
• Location relative to where you are

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Building a StructureFigure 4.9 Directory with
Subdirectories p.194
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Activity Creating More Subdirectories

• KEY CONCEPTS
• Created directories using
• absolute pathalways correct
• relative pathrelative to where you are
• First / is root directory
• Every other slash is a delimiter
• Compared the following two commands
• mkdir /mexicomkdir /floppy/mexico
• mkdir ../mexicols
• At command line can create intervening parent
  directories if they do not exist (use -p)

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The dot (.) and double-dot (..)Dot Addressing

• Dot Addressing is method of using dots to
  refer to directories
• Single dot (.)
• Specific name of current directory
• Double dot (..)
• Specific name of parent directory of current
  directory
• No spaces between dots

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The dot (.) and double-dot (..)Dot Addressing

• Can use .. as shorthand version of parent
  directory name to move up the directory tree
• Cannot use .. as a shortcut symbol to move down
  the hierarchy

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Activity Using the Double-dot

• KEY CONCEPTS
• Using the up arrow is equivalent to using dot
  dot in the Nautilus file manager
• Reviewed when and why you use the relative path,
  the absolute path
• Used dot addressing techniques

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Changing the Names of Directories

• Can change the names of directories
• In Nautilus file manager
• At the command line
• Syntax mv option source test

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Changing the Names of DirectoriesTable 4.3 mv
Options p. 202
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Activity Renaming Directories

• KEY CONCEPTS
• A directory is also a file
• Typing replaces selection
• May rename a file with the right-click menu

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Removing Directories

• Removing directories accomplished
• Using the Nautilus file manager
• At the command linetwo step process
• rm command to remove files
• rmdir command to remove empty directories
• Note Can remove directories only if they are
  empty and contain no hidden/or system files

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Removing Directories

• rmdir command
• Cannot be used with wildcards
• Default path used if path designator not
  included
• Syntax rmdir options directories

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Removing Directories

• When using Nautilus file manager or rmdir
  cannot remove
• Directory you are currently in (default)
• Root directory

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Removing DirectoriesTable 4.4 rmdir Options p.
204

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Activity Removing Directories

• KEY CONCEPTS
• Until trash is emptied can recover what
  files/folders are in the trash
• Cannot remove a directory you are in nor can you
  remove the default directory
• Create directory from top-down
• Remove directories from bottom up

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Removing Directories Recursively-Using rm rmdir

• Can remove directories recursively
• Using Nautilus file manager
• Using rm and rmdir at the command line

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Removing Directories Recursively-Using rm rmdir

• At command line
• Can delete directory structure only if
  directories are empty of files
• rmdir -p deletes empty parent directories

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Removing Directories Recursively-Using rm rmdir

• At command line
• rm used to remove files in parent directories
• Syntax rmoptions files
• -r (recursive) option
• If file is name of directory will remove entire
  directory structure and all its contents
• Useful but dangerous (very fast)
• -f optionwill delete even read-only files
  without prompting

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Removing Directories RecursivelyUsing rm
rmdirTable 4.5 rm Options p. 207
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Activity Removing Directories

• KEY CONCEPTS
• Used -v option to see what is occurring
• Used - p option to delete directory and its
  parent
• Used -r option to remove directory tree
  (remember this option is fast and dangerous)
• Used -f option which forces deletion

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Variables

• Can recognize default directory
• Operating system in a terminal window displays
  current location in the prompt
• Bash shell give information by use of
  environmental variables

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Variables

• Variables
• Value that can change with conditions or
  information passed to the program
• Symbol/name used to represent a value
• Shell variables
• Controls functionality of the shell
• Created at command line or in shell script

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Variables

• Shell Script
• Text file containing sequence of commands
• Provides ease in transferring values from one
  command to another
• Shell has ability to store data
• Takes form of two strings
• Name of variable
• Value of variable

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Variables

• Environmental variables
• Name (UPPERCASE) assigned to string (value) of
  data
• displays contents rather than name
• Examples
• HOME
• PATH
• PS1

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The PROMPT Variable

• Configuration of prompt determines how prompt
  looks.
• Environmental variables (PS1 and PS2) contain
  text displayed in terminal window

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The PROMPT Variable

• Environmental variable has special characters
• Will return a specified value
• Preceded by a \ and followed by a character
  indicating what is to be displayed

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The PROMPT VariableTable 4.6 Formatting
Characters for Prompt p. 211
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The PROMPT VariableTable 4.6 Formatting
Characters for Prompt p. 211
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The PROMPT Variable

• The default Red Hat prompt is \u_at_h \W

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Activity Changing the Prompt

• KEY CONCEPTS
• printenv command prints all or part of what is
  in the environment
• set command
• With no arguments/options prints all values of
  all variable known to the shell
• Options can be enabled/disabled
• To display value of any environmental variable
  use echo, the dollar sign, and then variable name

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Activity Changing the Prompt

• KEY CONCEPTS
• Compared \w with \W
• (tilde)
• Shorthand for directory or currently logged in
  user
• Can be used as shorthand for home directory

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Activity Changing the PromptTable 4.7 Red Hat
Linux/Bash Configuration Files p. 214
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Understanding the PATH Variable

• Executable files (commands) stored in
  directories.
• Common Linux/Unix command directories
• /bin
• /usr/bin

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Understanding the PATH Variable

• PATH variable specifies directories to search
  and order in which to search for a commandan
  executable program
• Colons separate directories in the PATH
• Operating system executes the first program
  match found in the path

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Activity Using the PATH Variable

• KEY CONCEPTS
• For each command keyed in directories searched
  will be ones listed in order from left to right
• Delimiter used to separate one directory name
  from another is the colon
• Can add permanent directory to search path by
  changing configuration file
• Can add a temporary directory to search path
  lasts only as long as you are in a work session

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Understanding the CDPATH Variable

• CDPATH
• List of directories separated by colons
• Set by user
• Allows shell search without entering entire path
  name
• Lasts until terminal session ends

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Activity Using the CDPATH Variable

• KEY CONCEPTS
• Set search path for directories
• (tilde)shorthand notation for home directory
• Colon used to separate directories
• Values for CDPATH lasts until terminal session
  ends