Learning UNIX

1
Learning UNIX

• CSWUG 2007
• Richard Clark
• Collaboratory for Advanced Computing
  Simulations
• Department of Physics Astronomy
• University of Southern California
• Email richarac_at_usc.edu

2
Outline

• Introduction to UNIX
• Text Editor - NANO
• Basic Commands
• File Manipulation
• Permissions
• Processes
• Important Utilities
• Running a Program
• Remote Login Procedures

3
Introduction to UNIX

• What is UNIX?
• UNIX is an operating system (OS) and
• set of related utility programs
• It is the manager of everything going on in your
  computer
• Advantages of UNIX
• Many Users can use the same computer at the same
  time
• Can run many different things simultaneously

4
How Things Work in UNIX

• A Few Terms to Know
• Shell
• The program you use to interact with the
  computer
• File
• Stored info and all your devices (like disk
  drives and printers)
• Processes
• All Programs that running
• Rules for Names
• Case Sensitive (ie. Happy.txt is different than
  happy.txt)
• Extensions Irrelevant (for now)

5
Using the Shell

• Login Procedure
• login
• password
• Changing your Password
• After logged in, type
• passwd
• (you will type in the old password once, and the
  new one twice)

6
Using Text Editor - NANO

• Start with
• nano - to start the editor with a new file
• nano filename - to start editing filename
• (creates if doesnt exist)
• The commands are listed at the bottom of the
  window
• Delete character d Ctrl-d
• Save o Ctrl-o
• Exit x Ctrl-x (also saves if desired)

7
Exercise Writing Files

• Type nano and create a file called - unix.notes
• Include in it answers to the following
• A Shell is
• A Process is
• Devices in UNIX are stored as
• Commands in UNIX are case-sensitive (T/F)
• Save your file.

8
Format of Commands

• General Format of Commands
• The command line cswug_at_machine1 cswug
• The command structure
• command options arguments
• Can have multiple options (-l -a) and arguments
  (file1.txt file2.txt), etc

9
Dealing with Files

• ls - lists files
• ls
• ls -a (lists all hidden system files too)
• mv - moves (and renames) file
• mv oldfile newfile
• cp - copies (renames) file
• cp oldfile newfile
• rm - deletes a file
• rm oldfile

10
Exercise Files

• Make 2 copies of your unix.notes with cp (call
  the copies unix2.notes and unix3.notes)
• Rename the unix2.notes to unix4.notes with mv
• Make sure you have 3 files with ls
• Remove the unix4.notes copy with rm
• Update your notes (in unix.notes)

11
Better Search Tactics

• Wild Cards ? and and
• Wild cards allow search for range of files
• ? any 1 character here
• file?.txt - selects file1.txt, but not
  file11.txt
• any of characters
• file.txt - selects file1.txt and file11.txt
• allows selection of certain characters
• file1-3.txt - selects file1.txt, file2.txt,
  file3.txt only

12
File Contents

• less - displays file contents
• less file1
• head - displays first 10 lines of file
• head file1
• tail - displays last 10 lines of file
• tail file1
• grep - search file for given pattern
• grep pattern file1
• diff - compares 2 files and tells if different
• diff file1 file2

13
Other Commands

• man - short manual on command
• man command
• learn - tutorial on how to use certain topics
• learn
• df - shows how much disk space is used
• df
• date - shows current date and time
• date
• shutdown -shuts machine down
• shutdown

14
Intro to Directories

• Above is the tree structure
• relative vs absolute pathway
• Special Directories
• / the root directory . the current
  directory
• the home directory .. the parent directory

15
Using Directories

• cd - changes directories
• cd directoryname
• pwd - display current path
• pwd
• mkdir - make new directory
• mkdir newdirectory
• rmdir - delete directory (requires that dir is
  empty)
• rmdir olddirectory

16
Exercise Directories

• Check current path with pwd
• Make a new directory with mkdir called unix/
• Change into that directory (cd) and make another
  directory called notes/
• Delete the notes/ directory with rmdir
• Go back to home directory with cd or cd ..
• Move (mv) your unix.notes from here to your new
  folder unix/

17
Permissions and Other Users

• Permissions describe who is allowed to read,
  write, or use your files.
• To check permissions of files in your directory,
  type
• ls l -displays permissions to all files in
  directory
• ls l file1 -displays permission to file1
• Results in form
• d-rwx-rwx-rwx owner size updated
  filename
• The first rwx is the permission for the owner
• the next is for those in your group
• the last is permission for everyone else
• Each rwx read write execute permissions
• If one of three is a -, then that user does not
  have permission to do that action

18
Changing Permissions

• Chmod -changes the permissions on a file
• chmod options who operationpermission
  file-list
• who u (user), g (group), o (other), a (all)
• operation (add permission), - (take away),
  (set)
• permission r (read), w (write), x (execute)
• Examples
• chmod a r file1 - gives the read option
  to everyone for file1
• chmod g -wx file2 -takes away the write and
  execute options
• from group on file2
• chown -changes owner of a file
• chown newowner file

19
User Accounts

• su -switch user (or super-user)
• su newperson
• useradd -adds new user
• useradd newperson
• userdel -deletes user account
• userdel oldaccount

20
Processes

• top - lists processes currently running (and get
  IDs)
• top
• (type q to get out of listing)
• ps - lists status of a process
• ps idnumber
• kill - kills a process
• kill idnumber
• killall - kills all processes
• killall

21
Important Utilities

• gzip - zips a number of files (adds gz to
  extension)
• gzip file1
• gunzip - unzips a file
• gunzip file1.gz
• tar - clumps all files into archive
• tar -cvf archivename filelist -creates an
  archive
• tar -xvf archivename -extracts files from
  archive

22
Running Programs

• Compiling a Program
• Note For the compiler, the extension (.c or
  .f90) DOES matter!
• gcc - C compiler
• gcc mainfile.c
• ifort - Fortran compiler
• ifort file.f90
• (The default name of a created program is
  a.out)
• Executing a Program
• ./ - Runs a compiled program
• ./a.out

23
Remote Login

• To login and work on a remote computer
• ssh - secure shell program
• ssh user_at_host
• -opens a shell (interface) to the other
  computer. Use this shell just as you would your
  first computer. Type exit to close the
  connection.
• To copy a file to a remote computer
• scp - secure copy program
• scp file user_at_host path
• scp file1 myname_at_cswug1.usc.edu
  /somedirectory/

24
Thanks!

• References
• Sobell, Mark G. A Practical Guide to Unix System
  V - 2nd ed.
• Nomura, Ken-ichi. Tutorial of UNIX/LINUX _at_
  CSWUG 2004
• Sharma, Ashish. General Reference

Questions?