Learn Regular Expression from Corey

正規表現で悩んでいるときに先生が勧めてくれたYouTube動画がすごく良かったので自分なりに内容をまとめました。

動画: Regular Expressions (Regex) Tutorial: How to Match Any Pattern of Text

Meta Characters (Need to be escaped)

.[{()/^$|?*+

If I want to search "Finxter.com", the way is Finxter\.com

If I want to search "Ha HaHa" with word boundary (\bHa), the The matches are "Ha Ha".

If I want to search numbers(321-555-4321 and 123.555.1234), the way is \d\d\d.\d\d\d.\d\d\d\d or \d\d\d[-.]\d\d\d[-.]\d\d\d\d.

TEL number example

1. 321-555-4321
2. 123.555.1234
3. 123*555*1234
4. 800-555-4321
5. 5. 900-555-4321

\d\d\d.\d\d\d.\d\d\d\d
\d\d\d[-.]\d\d\d[-.]\d\d\d\d
[89]00[-.]\d\d\d[-.]\d\d\d\d
[1-5]
[a-fA-F]
[^a-g]

Word example

1. cat
2. mat
3. pat
4. bat

• [^b]at: Get 1-3.

Meta Characters

• .: Any Character Except New Line
• \d: Digit (0-9)
• \D: Not a Digit (0-9)
• \w: Word Character (a-z, A-Z, 0-9, _)
• \W: Not a Word Character
• \s: Whitespace (space, tab, newline),
• \S: Not Whitespace (space, tab, newline),
• \b: Word Boundary
• \B: Not a Word Boundary
• ^: Beginning of a String
• $: End of a String
• []: Matches Characters in brackets
• [^ ]: Matches Characters NOT in brackets
• |: Either Or
• (): Group

Quantifiers:

• *(asterisk) - 0 or more
• + - 1 or more
• ? - 0 or one
• {3} - Exact Number
• {3,4} - Range of Numbers (Min, Max)

Name example

1. Mr. Schafer
2. Mr Smith
3. Ms Davis
4. Mrs. Robonson
5. Mr. T

• Mr\.? : Get 1, 2, 4, 5
• Mr\.?\s[A-Z]: Get 1, 2, 5
• Mr\.?\s[A-Z]\w+: Get 1, 2
• Mr\.?\s[A-Z]\w*: Get 1, 2, 5
• M(r|s|rs)\.?\s[A-Z]\w*: Get all 1-5

Email example

1. [e-mail]
2. [e-mail]
3. [e-mail]

• [a-zA-Z]+@[a-zA-Z]+\.com: Get 1
• [a-zA-Z.]+@[a-zA-Z]+\.(com|edu): Get 1, 2
• [a-zA-Z0-9.-]+@[a-zA-Z-]+\.(com|edu|net): Get all 1-3
• [a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+: Get all 1-3

URL example

1. https://www.google.com
2. http://coreyms.com
3. https://youtube.com
4. https://www.nasa.gov

• https?://(www\.)?(\w+)(\.\w+): Get all 1-4

• Replace with Group 1: $1. The result is...

  Group 1: www.
  Group 1:
  Group 1:
  Group 1: www.

Replace with Group 2: $2. The result is...

Group 2: google 
Group 2: coreyms
Group 2: youtube
Group 2: nasa

Replace with Group 3: $3. The result is...

Group 3: .com 
Group 3: .com
Group 3: .com
Group 3: .gov

Replace with $2$3. The result is...

google.com
coreyms.com
youtube.com
nasa.gov