Bash Scripting - making your life easier

A talk for the biggest java conference in Bulgaria - Java2Days

Transcript

2. We do tedious repetitive tasks all the time
4. But there is a solution!
5. Bash.
6. Bash scripting – making your life easier Preslav Mihaylov 16.10.2016, Java2Days Sofia, Bulgaria
7. /PreslavMihaylov /PreslavMihaylov Software Engineer Technical Trainer /PreslavMihaylov
8.  What is a shell  How do we interact with the shell  Introduction to Bash scripting  Exploring Bash script syntax  Real world issues  When not to use Bash  Exploring all the different commands  In-depth coverage of bash features Agenda
9. What is a shell
10. OS SHELL USER
11. How do we interact with the shell Live Demo
12. OK. So we can type in commands in the interactive shell
13. But how do we automate them?
14. Introduction to Bash scripting
15. Moving from the command prompt To a text file Live Demo
16. The shebang... #!/bin/bash  … defines the program which will interpret the script   … is stationed on the first line of the script 
17. Redirecting I/O  One of the most powerful features   Allows us to combine programs together
18. Keyboard echo Screen echo “Hello world”
19. Keyboard echo Screen echo “Hello world” > log.txt log.txt
20. Keyboard echo Screen grep “hello” <input.txt Screen Input.txt
21. echo Screen echo “Hello world” | grep “Hello” Screen grep Screen
22. Live Demo
23. Exploring Bash script syntax
24. Variables  How to declare them:  STR=Hello   How to use them:  echo $STR
25. How NOT to declare them  STR =Hello STR= Hello STR = Hello STR = Hello
26. How NOT to use them  echo $STR_pesho   Correct way:  echo ${STR}_pesho
27. Working with text  Parses text as is:  echo ’Hello $STR’   Interpolates text:  echo “Hello $STR”   Gets the output of the command:  echo “Hello $(cat name.txt)”
28. Live Demo
29. Making decisions  If <condition>; then  ...  elif <condition>; then  …  else  …  fi  Syntax:
30. Making decisions  The condition format depends on the brackets used   The brackets can be of many kinds. Depending on them you can do arithmetic expressions, regex, etc...   A short tutorial:  Bash scripting if statements
31. Live Demo
32. Repetition structures  for var in list; do …  done   while <condition>; do …  done  Syntax:
33. Repetition structures  The list is a string with whitespace (depends on IFS) separated values   The var is a shell variable which acts as an iterator over the list   The condition works the same way it works with Decision structures
34. Live Demo
35. Real world issues
36. Three points of view  The User   The Developer   The Sysadmin
37. The User wants to...  … avoid tedious tasks.  … automate his daily tasks.  … customize his shell the way he wants.
38. The Developer wants to...  … do his work in peace.  … build his project appropriately.  … tune up his OS a bit.
39. The Sysadmin wants to...  … automate his work in order to play Counter Strike.  … maintain a stable system.  … avoid dealing with Users.
40. Live Demo
41. When not to use Bash
42. Avoid using Bash...  … on Heavy tasks.  … when the script gets too big.
43. Resources  TLDP - Intro Bash Scripting  TLDP - Advanced Bash Scripting  From Bash to Z Shell 
44. The GUI makes the simple tasks - even simpler. The Shell makes the impossible tasks - possible
45. May the Bash be with you /PreslavMihaylov /PreslavMihaylov /PreslavMihaylov 16.10.2016, Java2Days Sofia, Bulgaria