UNIX Operating System

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UNIX Operating System

• Compe 111 Lab

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Software Classification
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Unix

• Unix is a complete multi-tasking and multi-user
  operating system. Many users may login to the
  unix system and each user may run multiple
  programs simultaneously.

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Unix
(Kernel)
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Kernel

• Kernel directs the hardware.
• File manager (reading writing files)
• Device drivers
• Memory manager
• Scheduler and dispatcher (Running processes with
  respect to priorities, time intervals and such)

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Shell

• Shell reads and executes commands types by the
  users. It acts as an interpreter between the user
  and the Unix kernel.
• It can be text based or with GUI (window manager)
• sh, bash, ksh, csh... are sample text shells

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Starting to Unix

• Through
• Start?Run... Type
• telnet 172.16.220.252
• This is the IP address of unix server in our
  operating systems laboratory.
• Username std01 (std02...std39)
• Password 111std01
  (111std02...111std39)
• Do not use std12

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Starting to Unix
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User accounts

• Your default shell might be different.
• Switch between sh, ksh, csh shells
• We will use bash
• Type bash in command line to switch to bash

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User accounts

• passwd for changing your passwords. It must be
  at least 6 character.
• Try to change your passwords as aaa111
• It will be asked twice.
• Now, turn back to your old passwords
• std01 ?111std01
• std02 ?111std02
• std39 ?111std39
• exit or logout is used to close the session

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User accounts

• pwd gives current working path
• date returns date and time of day
• cal returns the calendar for month
• cal, cal 2 (for feb.), cal 2006, cal 3 2008
• df returns the free disk space in kb

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User accounts

• who lists who is logged on the system
• whoami displays your user name
• w returns who is doing what on the system
• stty returns terminal status
• echo text displays the text as output

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Commands in Unix

• Syntax
• command
• command options argument
• command options argument1 argument 2
• ls (like dir in dos)
• ls al (lists all entities (files folders
  hiddens) with all attributes and specifications
  in long format)
• ls l temp (listing folder temp in long format)
• ls .txt (list the files ending with .txt)

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Commands in Unix

• Example
• drwxr-xr-x 3 std01 staff 512 Oct 17
  1613 temp
• d directory
• - file
• rwxr-xr-x owner-group-others
• r read
• w write
• x execute
• - not allowed
• rwxr-xr-x 755 rwxrwxrwx 777
• You may set permissions by chmod
• chmod 777 temp
• chmod 744 temp

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Commands in Unix

• Example
• drwxr-xr-x 3 std01 staff 512 Oct 17
  1613 temp
• 3 i-node number pointing the file. It is related
  to file allocation structure of unix. Keeps
  position, owner, structure, links, types etc.
• staff user type. (standard user, root...)
• 512 size in bytes
• Oct 17 1613 creation date and time
• temp name

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Getting help

• man is used to getting help
• man command
• man man
• man ls

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User accounts

• During login each shells executes a shell program
  (Bourne and Korn shells execute .profile). This
  is your startup file and keeps your programs to
  be run, variables.

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Variables

• Each shell variable has a name and value
  associated with it.
• To define a variable and set its value
• var_namevalue (for Bourne and Korn) or
• set var_namevalue (C and TC shells)

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Variables

• Example
• namebelinda
• surnameblack
• age18
• To see the values
• echo name
• echo age
• echo name surname age

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Environment Variables

• Some variables have special meaning to the shell
  and they are automatically set whenever you
  login. Might be kept in your .profile
• HOME path of your home directory
• PATH defines the directories searched when shell
  is looking for the file to execute when a process
  is to run.
• MAILMSG The message is given when you have an
  e-mail. e.g. You have a mail.
• TERM contains the code that indicates the make
  and model of the terminal you are using. Like,
  vt100, ansi...

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Environment Variables

• echo HOME
• echo PATH
• echo MAILMSG
• echo TERM

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Command History

• Type history to see your past actions.
• You can move between your actions using arrows.

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Processes and Scheduling

• ps lists running processes
• PID TTY TIME CMD
• 20883 pts/6 000000 bash
• PID process id. Unique to the process
• TTY terminal
• Time execution
• CMD process name
• ps e Show all processes

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Processes and Scheduling

• sleep 10 wait for 10 seconds.
• CtrlC (or CtrlZ) to interrup the current
  process
• sleep 150 runs the process at back ground.
  Allows you to execute other commands.
• You can see your background tasks by jobs
• You can also see them by ps

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Processes and Scheduling

• If you put a process at background and you want
  it to run after you logout, use
• nohup command arguments
• nohup sleep 1000 will prepare a file to be run
  after you leave the session.
• kill PID kills the processes with the specified
  ID.

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Processes and Scheduling

• ps to get PID of sleep process
• and kill it
• kill also resolves deadlock condition (when
  system in undecisive mode)

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Processes and Scheduling

• bg command is used to put a background task
• If you suspend a process by CtrlC (or CtrlZ),
  you can resume it by using bg.
• Now, run man ls
• Break it using CtrlC (or CtrlZ)
• 4 Stopped man ls
• 4 is jobs number.
• bg 4 is used to put the process back in ps

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Processes and Scheduling

• You may also set a list of jobs to be executed at
  a specifiec time using at command (scheduling).
• at 10am Jul 31
• or
• at 1pm tomorrow

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Processes and Scheduling

• First you will see a warning about which shell to
  be used for execution.
• Then you will type your commands
• atgt ls al
• atgt echo hello
• ctrl c or ctrlz to break scheduling
• It will be recorded to run later.
• atq lists all at jobs belonging to user
• atrm username removes all at jobs of user

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File system

• Unix keeps a hierarchical tree for file and
  directory sturcture
• root
• bin usr home lib
• user1 user2 user3

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File system

• /bin Unix system utilities, ls, date...
• /usr Additional user utilities
• /home User directories
• /lib Libraries such as C language
  and mathematics
• Files and folders have names upto 256 characters.
• Unix is case sensitive.
• Myfile ! myFile ! MYFILE

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File system

• Creating a file
• cat gt firstfile
• This is just a test
• CtrlD
• Appending a file
• cat gtgtfirstfile
• It is the second line of test file
• Here is the third line
• CtrlD
• Displaying content
• cat firstfile
• cat firstfile more page by page

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File system

• Creating a second file
• cat gt secondfile
• First line of second file
• ctrld
• Combining files
• cat firstfile secondfile gt thirdfile
• cat thirdfile

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File system

• Copying a file
• cp firstfile copyfirstfile
• Renaming (or moving) a file
• mv firstfile FirstFILE
• Sorting the contents of a file
• sort firstfile (firstfile is not updated)
• sort firstfile o output
• cat output

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File system

• Searching expression
• grep -i test firstfile
• Searches test in lines of firstfile
• grep -l test
• Searches all files including test
• Counting
• wc l firstfile counts lines
• wc w firstfile counts words
• wc c firstfile counts characters

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File system

• Removing files cannot be got back
• rm secondfile
• rm i thirdfile asks for sure?
• rm .doc removes all .doc documents

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File system

• Creating a directory
• mkdir project
• Moving a file to a folder
• mv firstfile project
• (cp firstfile project if you want to copy)
• ls l to see that firstfile is moved
• cd project to change current directory
• pwd to see where you are
• ls l to see firstfile is here
• cd .. (not cd..) to move one level above

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File system

• Renaming a directory
• mv project newproject
• Now project is changed as newproject
• Removing directories
• rmdir newproject it must be empty
• rmdir r newproject removing everything
  recursively

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Applications

• vi text editor
• vi deneme
• It has 2 modes command mode and insert mode
• Esc and then i is to switch to insert mode
• Esc to switch to command mode

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Applications

• In insert mode, you can type.
• In command mode, h(left), j(down), k (up) and l
  (right) are used.
• In command mode,
• X,x deletes characters. 3x deletes 3 char.
• dw deletes words
• dd deletes lines

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Applications

• In insert mode,
• w to save
• wq to save and exit
• q to exit
• q! to exit discarding changes after last save
• Use man vi for more information

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Applications

• Pico editor is an easy editor.
• pico deneme .txt
• After typing, all actions are done via
• Ctrl X, O, R, U ....