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![“Python [and other languages -me] scales up to
thousand of lines, shell script scales down to a
few keystrokes.”
– Somebody at Stack Overflow
Alas, I couldn’t find the link, not even the name of the user :(](https://image.slidesharecdn.com/shell-script-170623021620/85/Shell-Script-13-320.jpg)
![Pipes
$ cat phones.txt | grep '^P' | sed 's/ [0-9]+$/ ****/'
Pedro (81) 9 9653 ****
Paulo (81) 9 8614 ****
Paula (61) 9 8112 ****](https://image.slidesharecdn.com/shell-script-170623021620/85/Shell-Script-56-320.jpg)
Uploaded byAdam Victor Brandizzi
Shell Script
This document provides an introduction to shell scripting. It discusses how shell scripts can help automate tasks and make computers work for developers. Some key points covered include: - Shell scripts are useful for quick, one-off tasks and automating repetitive steps. They allow getting work done faster. - Common shell scripting tools like echo, cat, grep, sed, and awk are introduced along with examples of their usage. - Concepts like piping output between commands, command substitution, quoting, escaping and variables are explained. - The Unix philosophy of small, modular programs that work together is discussed in the context of shell script design.
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Shell Script
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- 5. Scripting is more practice thanconcepts.
- 6. How can shell scripthelp me?
- 7. “Many C/C++/Java candidates,even some with 10+ years of experience, would happily spend a week writing a 2,500-line program to do something you could do in 30 seconds with a simple Unix command.” – Steve Yegge https://sites.google.com/site/steveyegge2/five-essential-phone-screen-questions
- 8. How can shellscripts help me? ● As developers, we make computers work for others. ● Computers could work a lot for ourselves, too. ● Shell script is a faster way to get work done.
- 9.
- 10. Whatever you prefer! (Butwe will talk about Bash here.)
- 11. How good is shellscript?
- 12. How good isshell script? ● Very good for quick, one-off tasks. ● Great for small tasks. ● Also good to deal with a lot of files, download stuff. ● Great option to automate a set of steps. ● Can get confusing fast. Peter H. Salus. A Quarter-Century of Unix apud http://www.catb.org/~esr/writings/taoup/html/ch01s06.html
- 13. “Python [and otherlanguages -me] scales up to thousand of lines, shell script scales down to a few keystrokes.” – Somebody at Stack Overflow Alas, I couldn’t find the link, not even the name of the user :(
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- 15. Unix Philosophy ● Writeprograms that do one thing and do it well. ● Write programs to work together. ● Write programs to handle text streams. Peter H. Salus. A Quarter-Century of Unix apud http://www.catb.org/~esr/writings/taoup/html/ch01s06.html
- 16. Unix Philosophy ● Smallutilities. ● Pipes and redirects. ● “Everything is a file.” – Including standard input/output/error. Peter H. Salus. A Quarter-Century of Unix apud http://www.catb.org/~esr/writings/taoup/html/ch01s06.html
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- 18. echo ● Print contentto standard output.
- 19. echo $ echo Thisis my message. This is my message.
- 20. echo $ echo "Thisis my message." This is my message. $ echo 'This is my message.' This is my message.
- 21. echo $ echo -e'JavanC++' Java C++
- 22. cat ● Concatenate files. ●Good for showing content.
- 23. cat $ echo -e"JavanC++" > languages $ cat languages Java C++
- 24. cat $ echo -e"WindowsnLinuxnMac OS" > OSes $ cat languages OSes Java C++ Windows Linux Mac OS
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- 27. Quoting and Escaping $echo This is my message. This is my message. $ echo "This is my message." This is my message. $ echo 'This is my message.' This is my message.
- 28. $ echo Goodtimes (are coming) bash: syntax error next to unexpected `token' `(' $ echo "Good times (are coming)" Good times (are coming) $ echo 'Good times (are coming)' Good times (are coming) Quoting
- 29. $ echo Goodtimes (are coming) bash: syntax error next to unexpected `token' `(' $ echo "Good times (are coming)" Good times (are coming) $ echo 'Good times (are coming)' Good times (are coming) Quoting
- 30. $ echo Thisis a little star: * This is a little star: languages OSes $ echo 'This is a little star: *' This is a little star: * $ echo This is a little star: * This is a little star: * Escaping
- 31. What if myparameter has quotes?
- 32. $ echo "Thisis Dave's "situation."" This is Dave's "situation."
- 33. What if myparameter both types of quotes?
- 34. $ echo "Thisis Dave's situation." This is Dave's situation.
- 35. $ echo Thisis a "situation." This is a situation. $ echo 'This is a "situation."' This is a "situation." $ echo "This is "Dave's situation."" This is "Dave's situation". Quoting
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- 37.
- 38. $ VAR=this $ echoMy value is $VAR My value is this $ echo "My value is $VAR" My value is this $ echo 'My value is $VAR' My value is $VAR Variables
- 39. $ EXAMPLES=quotes $ echo"too ""many """$EXAMPLES"""""""" too many quotes $ echo '"too ""many """$EXAMPLES""""""""' "too ""many """$EXAMPLES"""""""" $ echo '"too ""many """'$EXAMPLES'""""""""' "too ""many """quotes"" Variables
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- 42. grep ● Search forlines in one or more files. – Or from standard input. ● “Basic” or “extended” regular expressions. – Or even plain strings and PERL regexes. ● Many options – Inverse match. – Only match. – Show line numbers...
- 43. grep $ cat phones.txt Pedro(81) 9 9653 7734 Paulo (81) 9 8614 1092 Paula (61) 9 8112 6751 Judite (61) 9 9612 9222
- 44. grep $ grep '(61)'phones.txt Paula (61) 9 8112 6751 Judite (61) 9 9612 9222 $ grep 'P.*o ' phones.txt Pedro (81) 9 9653 7734 Paulo (81) 9 8614 1092
- 45. grep $ cat phones2.txt John(732) 554 8749 Phillip (552) 982 9839 Paul (882) 830 3802 Jared (893) 923 3820 $ echo * languages name OSes phones2.txt phones.txt
- 46. grep $ grep Paul* phones2.txt:Paul (882) 830 3802 phones.txt:Paulo (81) 9 8614 1092 phones.txt:Paula (61) 9 8112 6751
- 47. sed ● A littleweird programming language. ● Most of the time, we use the s/// command. ● Can alter the file inline.
- 48. sed $ sed 's/Judite/Judith/'phones.txt Pedro (81) 9 9653 7734 Paulo (81) 9 8614 1092 Paula (61) 9 8112 6751 Judith (61) 9 9612 9222
- 49. sed $ cat phones.txt Pedro(81) 9 9653 7734 Paulo (81) 9 8614 1092 Paula (61) 9 8112 6751 Judite (61) 9 9612 9222 $ sed -i 's/Judite/Judith/' phones.txt $ cat phones.txt Pedro (81) 9 9653 7734 Paulo (81) 9 8614 1092 Paula (61) 9 8112 6751 Judith (61) 9 9612 9222
- 50. awk ● A full-fledgedprogramming language. – Similar to (predecessor of) Perl, PHP. – Most programmers would be comfortable with. ● Read files as tables. – Each line is a record. – Each space-separated part a column.
- 51. awk $ awk '$1== "Paul"{print}' * Paul (882) 830 3802 $ awk '$1 ~ "Paul"{print}' * Paul (882) 830 3802 Paulo (81) 9 8614 1092 Paula (61) 9 8112 6751
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- 53. Pipes ● Redirect standardoutput from one command to another command’s standard input. ● Can also redirect standard error, sure. ● This is how most of the magic happens :)
- 54. Pipes $ cat phones.txt Pedro(81) 9 9653 7734 Paulo (81) 9 8614 1092 Paula (61) 9 8112 6751 Judith (61) 9 9612 9222
- 55. Pipes $ cat phones.txt| grep '^P' Pedro (81) 9 9653 7734 Paulo (81) 9 8614 1092 Paula (61) 9 8112 6751
- 56. Pipes $ cat phones.txt| grep '^P' | sed 's/ [0-9]+$/ ****/' Pedro (81) 9 9653 **** Paulo (81) 9 8614 **** Paula (61) 9 8112 ****
- 57. Command Substitution ● Addsone command’s output to another command.
- 58.