Intro to Linux Shell Scripting

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Slides for "Intro to Linux Shell Scripting" given at the Hoosier Educational Computer Coordindator\'s meeting, Indianapolis, 90/13/2009

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Intro to Linux Shell Scripting

  1. 1. Shell Scripting An Introduction to  Linux Shell Scripting Vern Ceder Canterbury School, Fort Wayne Intro to Shell Scripting Vern Ceder Canterbury School
  2. 2. This talk ISN'T for # Experienced shell scripters # People who own T­shirts saying  “Go away or I will replace you  with a very small shell script” # Anyone with a favorite shell  hack they MUST share... ;) Intro to Shell Scripting Vern Ceder Canterbury School
  3. 3. This talk is for you if... # You can open a terminal # You can type # You're interested in how to  combine those two things to make  your life easier  Intro to Shell Scripting Vern Ceder Canterbury School
  4. 4. What's Coming # Why use the shell? # Basic shell commands # Combining shell commands # Creating simple scripts # Automation with cron Intro to Shell Scripting Vern Ceder Canterbury School
  5. 5. Do you... Intro to Shell Scripting Vern Ceder Canterbury School
  6. 6. $ Need to manage computers not on your  desk?   $ Need to perform complex operations,  on lots of files? $ Need to repeat the same operations  on a lot of machines? $ Wish that some of this routine stuff  could just happen? Intro to Shell Scripting Vern Ceder Canterbury School
  7. 7. What's a “shell”? # A program that uses (text)  commands to talk to the OS # DOS (e.g.) # sh, bash, csh, ksh, zsh, etc... # This talk will assume bash Intro to Shell Scripting Vern Ceder Canterbury School
  8. 8. Basic Shell Commands # Files – ls, cp, mv, rm, mkdir # Access – chmod, chown # Disks – df, mount  # Processes – ps, kill, fg, bg # Network – ifconfig, ping, tracepath Intro to Shell Scripting Vern Ceder Canterbury School
  9. 9. Take ls, for example # ls    list files # ls ­l list more info # ls ­a list ALL # ls ­t list by date # ls ­R list Recursive # ls ­latR or combine Intro to Shell Scripting Vern Ceder Canterbury School
  10. 10. More file commands # cp a b   copy files # mv a b move (rename) # rm a delete  # rm ­rf a remove EVERYTHING  (danger, danger) Intro to Shell Scripting Vern Ceder Canterbury School
  11. 11. Access commands # chown user:group a   change file owner # chmod ugo+rwx a change permissions Intro to Shell Scripting Vern Ceder Canterbury School
  12. 12. disk commands # df    get free space # du /folder get amount used # mount show/change disks  mounted Intro to Shell Scripting Vern Ceder Canterbury School
  13. 13. process commands # ps ax   show processes # kill processid kill a process # fg  foreground # bg  background Intro to Shell Scripting Vern Ceder Canterbury School
  14. 14. network commands # ifconfig   show interfaces # ping ping a host # tracepath  follow a packet Intro to Shell Scripting Vern Ceder Canterbury School
  15. 15. So you can... # Manage files # Monitor disks # Control user access # Manage/debug network connections Intro to Shell Scripting Vern Ceder Canterbury School
  16. 16. DANGER!  You can also... Completely destroy your system Don't experiment/practice as  root! Intro to Shell Scripting Vern Ceder Canterbury School
  17. 17. But how do you know  what does what? # Man – the best way to find out  what a command does # Apropos – the way to find the  right command # tldp.org – man pages and howto's # Google ;)  Intro to Shell Scripting Vern Ceder Canterbury School
  18. 18. So? How is this better than using a  file manager? # Powerful – you can do ANYTHING # Remote – you can do it from  ANYWHERE # “Combinable” (that's next) Intro to Shell Scripting Vern Ceder Canterbury School
  19. 19. The “unix idea” # Small, specific utilities # Text input/output # “pipes” to connect one utility  to another Intro to Shell Scripting Vern Ceder Canterbury School
  20. 20. Commands to pull  it all together # cat    dump file # grep  find a pattern # cut cut out a field # sort sort # uniq remove dupes # head, tail get part of file # more, less page through file Intro to Shell Scripting Vern Ceder Canterbury School
  21. 21. Introducing the “pipe” # | connects the output of one  command to the input of another # > (and >>) puts the output into  a file # < puts a file to input Intro to Shell Scripting Vern Ceder Canterbury School
  22. 22. For example... Find out who is hogging the home  disk... # du  # sort  # tail  # du ­cks * | sort ­rn | head Intro to Shell Scripting Vern Ceder Canterbury School
  23. 23. Another example... Who's tried to log into your box? # cat  # grep  # cut  # sort  # uniq  Intro to Shell Scripting Vern Ceder Canterbury School
  24. 24. cat /var/log/auth.log | grep  "Failed password" | grep ­v  "invalid" | cut ­d " " ­f 9,11 |  sort | uniq Intro to Shell Scripting Vern Ceder Canterbury School
  25. 25. Scripts # To avoid retyping (and sometimes  refiguring out) # To handle more complex chores Intro to Shell Scripting Vern Ceder Canterbury School
  26. 26. Creating a simple script # Text file (text editor) # The “shebang” line # Shell commands # Make it executable Intro to Shell Scripting Vern Ceder Canterbury School
  27. 27. “space hog” as script #!/bin/bash du ­cks $1 | sort ­rn | head Intro to Shell Scripting Vern Ceder Canterbury School
  28. 28. “login finder” as script Login finder as a script cat $1 | grep "Failed password"   | grep ­v "invalid" |  cut ­d " " ­f 9,11 |grep $2 |  sort | uniq Intro to Shell Scripting Vern Ceder Canterbury School
  29. 29. What I didn't cover (a very partial list) # find # editors  # tar # Sed & awk # environment  # cron & crontab vars # loops  # echo  # if  # sleep  # test ( [ ] ) Intro to Shell Scripting Vern Ceder Canterbury School
  30. 30. But what about automation? What if you need to repeat the  same script every month? Every  week? Every day? Every hour?  Every minute? Intro to Shell Scripting Vern Ceder Canterbury School
  31. 31. Automating with cron # cron lets you run scripts at any  time, as any user Intro to Shell Scripting Vern Ceder Canterbury School
  32. 32. Print Resources # Classic Shell Scripting, Robbins & Beebe,  O'Reilly # Think Linux, Jon Lasser, QUE # UNIX Hints and Hacks, Kirk Waingrow, QUE # Linux in a Nutshell, Ellen Siever, et al.  O'Reilly # Many books on Linux/UNIX automation and  administration Intro to Shell Scripting Vern Ceder Canterbury School
  33. 33. Web Resources # See http://tech.canterburyschool.org/tech/shell  # Google “linux shell scripting” or the like Intro to Shell Scripting Vern Ceder Canterbury School
  34. 34. Video Resources # http://video.google.com  Search for “linux shell scripting tutorial” Intro to Shell Scripting Vern Ceder Canterbury School

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