1. Review Please hand in your practicals and homework Regular Expressions with grep

2. Today Quizzes Back Extra Credit More regular expressions – sed Cheatsheets! And better!

3. Extra Credit Whitepaper is now marketing – Interpreting them is fun (sometimes) I want (in no more than two pages) – OS and version needed – Dependencies – “Business Case” – what business sectors & what size companies it’s targeted at, as well as the purpose and benefits – Limitations or “gotchas” Get a holistic view of a Linux-based toolset, how it fits into a company, etc…

4. So Compare 2 Whitepapers Either of these: Implementing RHEL 6 on HP Servers Intel HA RHEL Solution To either of these: RHEL Value Compared to Win2k8 RHEL Migration Best Practices

6. Quick Refresh The grep commands allows for ‘regular expressions’ Sets of characters that allow us to define what to match and print – Static characters don’t change – Metacharacters allow for more broad matching – [] matches on one character – Can match on several different things – [A-Zqpr4-8] will match any uppercase letter OR q OR p OR r OR 4, 5, 6, 7, OR 8

7. Character Classes We can capture “digits” like 1, 42, or 7656784 – \d We can capture “word characters” like a, the, supercalafragilisticexpalidocious, and asdfjkl – \w We can capture “whitespace” like spaces, tabs, and “newlines” – \s \d and \w look between whitespaces

8. Character Type Opposites We can capture “non-digits” like whitespace or letter characters – \D We can capture “non- word characters” like digits and whitespaces – \W We can capture “non-whitespace” like numbers and letters – \S

9. Character Class Practice grep ‘\w’ teams.txt What is the command to match any line that starts with a digit?

10. Implementations Each language implements regex’s differently – PERL, Python, Shell, Java, C++, Ruby, etc… For example, I can’t explain this: \d should be ‘digit’ but I don’t see one in there \D non-digit returns NOTHING

11. sed So grep deals with lines which makes manipulating data difficult There are ‘capture groups’ in grep the () – so ([A-Za-z]+) would catch any letter collection But how would you replace? So we have sed Stands for ‘stream editor’ Same thing, on any match, perform an action

12. sed breakdown First – let’s match (like grep) Usage: sed ‘ / / ’ grep ‘[Ss]eattle’ teams.txt sed -n ‘/[Ss]eattle/p’ teams.txt -n suppresses full output (the rest of the file) ‘/[Ss]eattle is our regex /p’ is print teams.txt is our file

13. sed matching sed -n ‘/[Ss]eattle/p’ teams.txt Without –n a copy of the file is printed, and the matches are duplicated; with –n just matches are printed Between ‘/ and /p’ is our regex [Ss]eattle – same as with grep The /p’ closes the regex and gives an action – print; this overrides the –n so our matches go to STDOUT

14. Only Difference is –n

15. So What Does This Do? sed -n ‘/[s]ea/p’ teams.txt sed -n ‘/^Bears.*Superbowl$/p’ inMyDreams.txt

16. sed replacement But sed is mostly used for replacing Usage: sed ‘ / / / ’ sed ‘s/sea/Sea/g’ teams.txt No flag ‘s/ is substitute sea/ is what we’re matching on Sea/ will replace what we match on g’ is ‘global’ – do all; not just one teams.txt is our file

17. Your Turn Again sed ‘s/Chicago Bears/Best Team Ever/g’ teams.txt Our ‘start’ script we made isn’t working. What is the regex to match anything not starting with a S or a K? ls /etc/rc3.d |

18. Extremely Powerful The sed utility is frequently said to be a min- programming language in itself These are the basic usages we will frequent Cheatsheet!

19. Regex Cheatsheet “Anchors” - ^StartAnchor and EndAnchor$ “Sample Patters” – Examples! “Character Classes” - \d \w \s “Quantifiers” - * and + and more “Ranges” – [0-9] [a-z] etc… “Metacharacters” – bottom left We’re not covering POSIX Character Classes, Assertions, String Replacements, or most Special Characters

20. Finally Online Regex Utility http://boredwookie.net/index.php/blog/onlin e-bash-regex-checker/ http://boredwookie.net/index.php/blog/onlin e-bash-regex-checker/ – Will break down a regex and tell you what each part does – This means I’ll probably ask you to create your own – But then you can test yours on that utility – And you should use it on the homework/practical

21. No Class Monday It’s Memorial Day – You can come, I won’t be here And I will not be responsive this weekend – My brother-in-law is forcing me to go to Packer territory  – I will try to have everything graded on Wednesday, it may not happen

22. Own Study sed http://www.grymoire.com/Unix/Sed.html “Sed is the ultimate stream editor. If that sounds strange, picture a stream flowing through a pipe. Okay, you can't see a stream if it's inside a pipe. That's what I get for attempting a flowing analogy. You want literature, read James Joyce. Anyhow, sed is a marvelous utility. Unfortunately, most people never learn its real power. The language is very simple, but the documentation is terrible. The Solaris on- line manual pages for sed are five pages long, and two of those pages describe the 34 different errors you can get. A program that spends as much space documenting the errors as it does documenting the language has a serious learning curve.”