Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Notation conventions and modes

From: Using Regular Expressions

Video: Notation conventions and modes

Now that we have a text editor, I just wanted to make a couple of notes about the conventions that we're going to be using throughout this tutorial. The first is that whenever we have a regular expression you're going to see it inside forward slashes. So /abc/, abc would be the regular expression. This notation with the two forward slashes is a convention, and it's used all the time. You'll see regular expressions inside those forward slashes, and it really comes back from the very beginnings of regular expressions. You'll remember when I told you about the history, I said that was traditionally in the ed text editor g/ and then the regular expression /p. So that's where those forward slashes come from.

Notation conventions and modes

Now that we have a text editor, I just wanted to make a couple of notes about the conventions that we're going to be using throughout this tutorial. The first is that whenever we have a regular expression you're going to see it inside forward slashes. So /abc/, abc would be the regular expression. This notation with the two forward slashes is a convention, and it's used all the time. You'll see regular expressions inside those forward slashes, and it really comes back from the very beginnings of regular expressions. You'll remember when I told you about the history, I said that was traditionally in the ed text editor g/ and then the regular expression /p. So that's where those forward slashes come from.

However, when you use these in that regexPal that we're working with, you will not use the forward slashes. The forward slashes do not get entered in there, just the actual regular expression itself. Okay, so everything in between there is what you're going to input. The same thing, with the text string, whenever you see a text string on the screen, you're going to see it with quotes around it, but when you enter it into regexPal, you're going to enter it without the quotes, just abc. But when you see quotes around it like that, you'll know that it's a string.

So with the slashes on either side, it tells you it's a regular expression; the quotes tell you that it's a text string. Now if you're using another tool besides the regexPal tester and you're using these in another language, that language may require you to put your regular expression inside slashes, or your string inside quotes. You'll need to do that as is appropriate for that language. Now there's another important notation convention that you should know about, which is modes. Regular expression comes in several different modes. There's the Standard mode, which is just the regular expression by itself.

There is a Global mode, a global search, where the g comes after it instead of being before it, like it used to be back in the UNIX days. We put after it; that lets us know it's going to global. An i that tells us it's going to be case-insensitive. m is for Multiline mode, and S for Dot-matches-all mode. We'll talk about those a little later on, but I just want you to see that the mode goes right after those slash. It's not actually part of the regular expression; it's a modifier for the way that this regular expression ought to be handled. Now let's take a look at regexPal and look how these are implemented there.

Now in regexPal, you can see that those modes are up here across the top. So, if we're talking about something in Case-insensitive mode, well then we need to check that. That's the equivalent of putting the i after the slash. Actually it's equivalent of putting bot the g and the i after the slash since they're both checked. If we uncheck Global, now it's only the i, and so on, with the m and the s as well. In the online version of this tool, remember, Global is hidden. It's always assumed to be a global search. That's not a big deal. I just wanted to be able to demonstrate to you a little later on what the difference is between a regular search and a global search.

So that's how you enable these different modes in the regexPal, and most other programming languages and tools are going to have some way that you can get to these different modes and enable them. For now I just wanted you to understand what the standard notation is and how they're normally handled and then see how they're handled in regexPal.

Show transcript

This video is part of

Image for Using Regular Expressions
Using Regular Expressions

59 video lessons · 11681 viewers

Kevin Skoglund
Author

 
Expand all | Collapse all
  1. 2m 18s
    1. Welcome
      56s
    2. Using the exercise files
      1m 22s
  2. 19m 55s
    1. What are regular expressions?
      3m 20s
    2. The history of regular expressions
      6m 40s
    3. Regular expression engines
      2m 44s
    4. Installing an engine
      4m 5s
    5. Notation conventions and modes
      3m 6s
  3. 21m 23s
    1. Literal characters
      6m 39s
    2. Metacharacters
      2m 1s
    3. The wildcard metacharacter
      4m 31s
    4. Escaping metacharacters
      4m 53s
    5. Other special characters
      3m 19s
  4. 31m 26s
    1. Defining a character set
      5m 49s
    2. Character ranges
      4m 49s
    3. Negative character sets
      4m 53s
    4. Metacharacters inside character sets
      5m 12s
    5. Shorthand character sets
      6m 30s
    6. POSIX bracket expressions
      4m 13s
  5. 36m 38s
    1. Repetition metacharacters
      7m 17s
    2. Quantified repetition
      6m 59s
    3. Greedy expressions
      6m 27s
    4. Lazy expressions
      6m 46s
    5. Using repetition efficiently
      9m 9s
  6. 20m 24s
    1. Grouping metacharacters
      4m 14s
    2. Alternation metacharacter
      4m 54s
    3. Writing logical and efficient alternations
      7m 33s
    4. Repeating and nesting alternations
      3m 43s
  7. 19m 19s
    1. Start and end anchors
      7m 21s
    2. Line breaks and Multiline mode
      4m 41s
    3. Word boundaries
      7m 17s
  8. 23m 33s
    1. Backreferences
      8m 57s
    2. Backreferences to optional expressions
      3m 51s
    3. Finding and replacing using backreferences
      7m 16s
    4. Non-capturing group expressions
      3m 29s
  9. 32m 31s
    1. Positive lookahead assertions
      6m 39s
    2. Double-testing with lookahead assertions
      7m 16s
    3. Negative lookahead assertions
      6m 10s
    4. Lookbehind assertions
      6m 26s
    5. The power of positions
      6m 0s
  10. 13m 13s
    1. About Unicode
      4m 19s
    2. Unicode in regular expressions
      4m 41s
    3. Unicode wildcards and properties
      4m 13s
  11. 1h 55m
    1. How to use this chapter
      5m 38s
    2. Matching names
      6m 33s
    3. Matching postal codes
      8m 54s
    4. Matching email addresses
      5m 0s
    5. Matching URLs
      8m 1s
    6. Matching decimal numbers and currency
      6m 45s
    7. Matching IP addresses
      7m 10s
    8. Matching dates
      7m 49s
    9. Matching times
      8m 59s
    10. Matching HTML tags
      8m 34s
    11. Matching passwords
      6m 49s
    12. Matching credit card numbers
      9m 36s
    13. Finding words near other words
      6m 38s
    14. Formatting with Search and Replace, pt. 1
      7m 22s
    15. Formatting with Search and Replace, pt. 2
      4m 15s
    16. Formatting with Search and Replace, pt. 3
      7m 10s
  12. 47s
    1. Goodbye
      47s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ.

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Using Regular Expressions.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferencesfrom the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Are you sure you want to delete this note?

No

Your file was successfully uploaded.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.