LPI Linux Certification

1
LPI Linux Certification

• Chapter 1
• GNU and Unix Commands

2
Objectives

• Understanding and use of the Command Line
• Use of Text Streams and Processing Filters
• Basic File Management
• Using Streams , Pipes and redirects
• Create, change and kill processes
• Change the Priority of a process
• Using regular expressions

3
The Command line

• System interface is the Shell on Linux it's Bash
• Shell Command interpertur.

4
Shell Variable Basics

• PS1 contains the system prompt
• Uses echo to display value of any shell
  variable
• Example echo PS1
• PATH
• The path variable contains information used by
  the shell to find and launch programs or commands.

5
Shell Basics

• Export
• To make a variable available to the system use
  the export command
• Example export Javapath

6
Entering commands

• Commands consist of 4 general components
• A valid command(shell or program or script) found
  along the PATH of directories listed in the PATH
  variable
• Command options
• Argument , such as file names
• Line acceptance , the enter key.

7
Entering multiple commands

• Commands can be entered interactively by using
  the programming feature of the shell
• Multiple command can also be entered on the same
  line separated by a semicolon.
• Example lsps

8
Command History and Editing

• You can use command history to recall recent
  typed commands.
• The size of the history is controlled by the
  HISTFILE shell variable. Set by default to 500
  lines . You can adjust this by adjusting
  HISTFILE.
• Use the history command to view the history file.

9
History expanders

• !! most recent command
• !n refers to command n from the history
• ! -n current command minus n from history
• ! string most recent command starting with
  string
• !? String most recent command containing string
• string1string2 Substitution of string one
  for string two.

10
History editing

• Control- P or Up Arrow , gives previous .
• Control-n or Down Arrow , next .
• Control-b or Left , one char left.
• Control-f or Right , one char right.
• Control-a , beginning of line .
• Control-e , end of line
• Additional command on page 18 of text.

11
Processing Text Streams Using Text Processing
Filters

• cut,expand,
• fmt,head,join,
• nl,od,paste,pr,
• split,tac,
• tail,tr,wc,
• Xargs.

12
Some commonly used Text-Filters

• head prints the first few lines of a file or
  files
• Syntax head options files
• Tail prints the last few lines of a file.
• Example tail -f /var/log/messages
• This would allow you to see entries into the
  log files as the were occurring. The -f switch
  means follow.

13
Sed or Stream editor

• Is intended as a text filter
• Can be called from the command line or from a
  file
• Uses regular expressions
• Useful in doing substitution or removals of know
  text from a file or groups of files.

14
Preform Basic File Management

• File system Objects
• Directories and files
• Inodes
• Commands

15
File System Objects

• File system is shaped like a Tree
• It consist of object that contain other objects

16
Directories and Files

• Directories are objects intended to contain other
  objects
• Files are objects intended to contain
  information
• The top of the directory is called the root it
  is represented by the /
• All other objects can be referenced by there
  relationship to root in tree like manner.

17
Inodes

• Inodes are the objects that hold the
  identification information about object in the
  tree. Such as location on the disk , modification
  time and security settings.
• Each ext2 file system is created with a finite
  number of inodes

18
Management Commands

• CP
• MKDIR
• MV
• RM
• RMDIR
• TOUCH

19
Copy (cp)

• cp options file1 file2
• -f force overwrite
• -i prompt interactively before proceeding
• -p Preserve all file attributes such as ownership
  and permissions as well as time stamp
• -r -R recursively copy directories
• -v Display the name before copying

20
Make Directory (mkdir)

• mkdir options directories
• Make one or more directories , you must have
  write permissions in the directory your trying to
  create more directories in.
• -m set the access mode for directory
• -p Create parent directory if needed
• , is used as a short cut to user home directory

21
Move (mv)

• Move or rename files and directories
• mv options source target
• -f Force the move even if target exist,
  suppressing warning messages
• -i Query interactively before moving file.

22
Remove (rm)

• Delete one or more files
• rm options files
• To remove a file you must have write permission
  in the directory that holds the file.
• -d removes directory that are not empty
• -f Force removal with out prompting
• -i interactive mode
• -r, -R if file is directory recursively remove
  all contents.

23
Remove Dir (rmdir)

• rmdir options directories
• Delete directories that must be empty
• -p Remove any intervening parent directories
  that become empty as a result.

24
Touch

• touch options files
• -a Change only the access time
• -m change only modification time
• -t timestamps

25
Wildcards

• ?
• characters
• !characters
• a-z
• !a-z
• frag1,frag2,frag3...

26
Using Unix Streams,Pipes, and Redirects

• Standard I/O and default file descriptors
• Pipes
• Redirection

27
Standard I/O

• Standard input ( stdin) default is keyboard
  also known as file descriptor 0.
• Standard output (stdout) default is the screen
  also known as file descriptor 1.
• Standard error (stderr) default is also the
  screen also known as file descriptor 2.
• All three streams may be redirected at will.

28
Pipes

• Pipes take output from one program and Pipe it
  into another program , thus standard output from
  a program can become standard input to another
• By chaining the output of one command to the
  input of another command you can produce some
  very powerful applications .

29
Redirection

• Use redirection to send standard output to
  another place like a file.
• Shell redirecting operators are gt , gtgt , lt and
• See table 1-10 for useful Standard I/O
  redirection operator syntax

30
Tee

• Read from standard input and write to both
  standard output and one or more files.
• tee options files
• -a Append to files rather than overwrite.

31
Create, Monitor and Kill Processes

• What are processes
• Process monitoring
• Signaling Active Processes
• Terminating Processes
• Shell Job Control

32
What are Processes

• Every command or program executed on your
  operating system is a process
• Each has these quality's
• A lifetime , process ID , user and group ID,
  parent process ID, environment and current
  working directory.

33
Process Monitoring

• ps options
• Generates a one time snapshot of current
  processes.
• The most common form is ps -aux
• See manual for all the options , man ps.
• pstree options piduser
• Shows a tree representation of the processes ,
  similar to using ps -f

34
Top

• top command -line options
• Produces a continually updated display of all
  processes .
• Has an interactive mode allowing you to enter
  commands such as kill .
• Displays most of the same information as ps does.

35
Signaling Active Processes

• All processes listen for signals .
• Signals are numeric integer messages
• Most common used signals are HUP,INT,KILL,TERM,TS
  TP.
• Each have a corresponding number 1,2,9,15,and 18
  respectively.
• To see all the signal on your machine type
  kill -l for a list.

36
Kill

• Kill is used to stop a process or series of
  processes.
• Kill -s sigspec -sigspec pids
• See examples in the book
• Use ps or top to identify the process ID and then
  use the kill command to kill it .
• Kill -15 1001 , this means kill using the sigterm
  signal 15 the process 1001 .

37
Shell Job Control

• Allows you to place executing programs in the
  background and bring them into the foreground
• The shell command netscape place the
  netscape program in the background , it returns a
  job number and a PID number.
• Use the bg , fg and jobs commands to control
  background jobs.

38
Modify Process Execution Priorities

• Be nice use nice and renice
• Nice , assigns a priority number for program
  execution at the time it is executed. Renice is
  used to change the priority of a running program.
• Nice numbers range from -20 to 19 the lower the
  number the higher it's priority
• Only root can lower a nice number
• All user processes start at zero (0)
• See the book for syntax instruction

39
Making use of Regular Expressions

• Regular Expression
• Regular expression syntax
• Using grep
• Using sed
• Quoting

40
What are Regular expressions

• Regular Expressions are strings used in matching
  operations . The values inside the regular
  expression is used to search for or match a
  string.
• Regular expressions make extensive use of place
  holders and wildcards , as well as reserve
  symbols to represent actions and values.

41
Regular expression syntax

• Methacharacters , Characters that take on
  special meaning .
• the beginning of a line or end of a line.
  See table 1-12 , 1-13,and 1-14 for a expanded
  list
• Literals everything not a Methacharacter.
• Position Anchors , such as or .
• Character sets , used to match text
• Modifiers , change the meaning of other
  characters in the expression.

42
Grep

• Syntax grep options regex files
• Grep evolved from a line editor (ed) command into
  a utility of it's own.
• Used to search files or standard input for lines
  containing a match of the regular expression

43
Grep Options

• -c Display only a count of the lines that match
• -h Display matched lines
• -i ignore case
• -n display match lines with line numbers
• -v print all lines that do not match the regexp

44
Quoting

• To use Regular expression on the command line
  with grep and sed you must escape those
  Metacharacters you don't want the shell to
  expand.
• The backslash \ is used \
• Single quotes ''
• Double quotes
• All stop the shell from expanding them .