9.13. Match INI Section Headers
by Steven Levithan, Jan Goyvaerts
Regular Expressions Cookbook, 2nd Edition
- Regular Expressions Cookbook
- Preface
- 1. Introduction to Regular Expressions
- 2. Basic Regular Expression Skills
- 2.1. Match Literal Text
- 2.2. Match Nonprintable Characters
- 2.3. Match One of Many Characters
- 2.4. Match Any Character
- 2.5. Match Something at the Start and/or the End of a Line
- 2.6. Match Whole Words
- 2.7. Unicode Code Points, Categories, Blocks, and Scripts
- 2.8. Match One of Several Alternatives
- 2.9. Group and Capture Parts of the Match
- 2.10. Match Previously Matched Text Again
- 2.11. Capture and Name Parts of the Match
- 2.12. Repeat Part of the Regex a Certain Number of Times
- 2.13. Choose Minimal or Maximal Repetition
- 2.14. Eliminate Needless Backtracking
- 2.15. Prevent Runaway Repetition
- 2.16. Test for a Match Without Adding It to the Overall Match
- 2.17. Match One of Two Alternatives Based on a Condition
- 2.18. Add Comments to a Regular Expression
- 2.19. Insert Literal Text into the Replacement Text
- 2.20. Insert the Regex Match into the Replacement Text
- 2.21. Insert Part of the Regex Match into the Replacement Text
- 2.22. Insert Match Context into the Replacement Text
- 3. Programming with Regular Expressions
- Programming Languages and Regex Flavors
- 3.1. Literal Regular Expressions in Source Code
- 3.2. Import the Regular Expression Library
- 3.3. Create Regular Expression Objects
- 3.4. Set Regular Expression Options
- 3.5. Test If a Match Can Be Found Within a Subject String
- 3.6. Test Whether a Regex Matches the Subject String Entirely
- 3.7. Retrieve the Matched Text
- 3.8. Determine the Position and Length of the Match
- 3.9. Retrieve Part of the Matched Text
- 3.10. Retrieve a List of All Matches
- 3.11. Iterate over All Matches
- 3.12. Validate Matches in Procedural Code
- 3.13. Find a Match Within Another Match
- 3.14. Replace All Matches
- 3.15. Replace Matches Reusing Parts of the Match
- 3.16. Replace Matches with Replacements Generated in Code
- 3.17. Replace All Matches Within the Matches of Another Regex
- 3.18. Replace All Matches Between the Matches of Another Regex
- 3.19. Split a String
- 3.20. Split a String, Keeping the Regex Matches
- 3.21. Search Line by Line
- Construct a Parser
- 4. Validation and Formatting
- 4.1. Validate Email Addresses
- 4.2. Validate and Format North American Phone Numbers
- 4.3. Validate International Phone Numbers
- 4.4. Validate Traditional Date Formats
- 4.5. Validate Traditional Date Formats, Excluding Invalid Dates
- 4.6. Validate Traditional Time Formats
- 4.7. Validate ISO 8601 Dates and Times
- 4.8. Limit Input to Alphanumeric Characters
- 4.9. Limit the Length of Text
- 4.10. Limit the Number of Lines in Text
- 4.11. Validate Affirmative Responses
- 4.12. Validate Social Security Numbers
- 4.13. Validate ISBNs
- 4.14. Validate ZIP Codes
- 4.15. Validate Canadian Postal Codes
- 4.16. Validate U.K. Postcodes
- 4.17. Find Addresses with Post Office Boxes
- 4.18. Reformat Names From “FirstName LastName” to “LastName, FirstName”
- 4.19. Validate Password Complexity
- Problem
- Solution
- Length between 8 and 32 characters
- ASCII visible and space characters only
- One or more uppercase letters
- One or more lowercase letters
- One or more numbers
- One or more special characters
- Disallow three or more sequential identical characters
- Example JavaScript solution, basic
- Example JavaScript solution, with x out of y validation
- Example JavaScript solution, with password security ranking
- Discussion
- Variations
- See Also
- 4.20. Validate Credit Card Numbers
- 4.21. European VAT Numbers
- 5. Words, Lines, and Special Characters
- 5.1. Find a Specific Word
- 5.2. Find Any of Multiple Words
- 5.3. Find Similar Words
- 5.4. Find All Except a Specific Word
- 5.5. Find Any Word Not Followed by a Specific Word
- 5.6. Find Any Word Not Preceded by a Specific Word
- 5.7. Find Words Near Each Other
- 5.8. Find Repeated Words
- 5.9. Remove Duplicate Lines
- 5.10. Match Complete Lines That Contain a Word
- 5.11. Match Complete Lines That Do Not Contain a Word
- 5.12. Trim Leading and Trailing Whitespace
- 5.13. Replace Repeated Whitespace with a Single Space
- 5.14. Escape Regular Expression Metacharacters
- 6. Numbers
- 6.1. Integer Numbers
- 6.2. Hexadecimal Numbers
- 6.3. Binary Numbers
- 6.4. Octal Numbers
- 6.5. Decimal Numbers
- 6.6. Strip Leading Zeros
- 6.7. Numbers Within a Certain Range
- 6.8. Hexadecimal Numbers Within a Certain Range
- 6.9. Integer Numbers with Separators
- 6.10. Floating-Point Numbers
- 6.11. Numbers with Thousand Separators
- 6.12. Add Thousand Separators to Numbers
- 6.13. Roman Numerals
- 7. Source Code and Log Files
- 8. URLs, Paths, and Internet Addresses
- 8.1. Validating URLs
- 8.2. Finding URLs Within Full Text
- 8.3. Finding Quoted URLs in Full Text
- 8.4. Finding URLs with Parentheses in Full Text
- 8.5. Turn URLs into Links
- 8.6. Validating URNs
- 8.7. Validating Generic URLs
- 8.8. Extracting the Scheme from a URL
- 8.9. Extracting the User from a URL
- 8.10. Extracting the Host from a URL
- 8.11. Extracting the Port from a URL
- 8.12. Extracting the Path from a URL
- 8.13. Extracting the Query from a URL
- 8.14. Extracting the Fragment from a URL
- 8.15. Validating Domain Names
- 8.16. Matching IPv4 Addresses
- 8.17. Matching IPv6 Addresses
- 8.18. Validate Windows Paths
- 8.19. Split Windows Paths into Their Parts
- 8.20. Extract the Drive Letter from a Windows Path
- 8.21. Extract the Server and Share from a UNC Path
- 8.22. Extract the Folder from a Windows Path
- 8.23. Extract the Filename from a Windows Path
- 8.24. Extract the File Extension from a Windows Path
- 8.25. Strip Invalid Characters from Filenames
- 9. Markup and Data Formats
- Processing Markup and Data Formats with Regular Expressions
- 9.1. Find XML-Style Tags
- 9.2. Replace <b> Tags with <strong>
- 9.3. Remove All XML-Style Tags Except <em> and <strong>
- 9.4. Match XML Names
- 9.5. Convert Plain Text to HTML by Adding <p> and <br> Tags
- 9.6. Decode XML Entities
- 9.7. Find a Specific Attribute in XML-Style Tags
- 9.8. Add a cellspacing Attribute to <table> Tags That Do Not Already Include It
- 9.9. Remove XML-Style Comments
- 9.10. Find Words Within XML-Style Comments
- 9.11. Change the Delimiter Used in CSV Files
- 9.12. Extract CSV Fields from a Specific Column
- 9.13. Match INI Section Headers
- 9.14. Match INI Section Blocks
- 9.15. Match INI Name-Value Pairs
- Index
- About the Authors
- Colophon
- Copyright
INI section headers appear at the beginning of a line, and are
designated by placing a name within square brackets (e.g., [Section1]). Those rules are simple to
translate into a regex:
^[[^] ]+]
| Regex options: ^ and $ match at line breaks |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
There aren’t many parts to this regex, so it’s easy to break down:
The leading ‹
^› matches the position at the beginning of a line, since the “^ and $ match at line breaks” option is enabled.‹
[› matches a literal[character. It’s escaped with a backslash to prevent[from starting a character class.‹
[^] ]› is a negated character class that matches any character except], a carriage return (+› quantifier lets the class match one or more characters, which brings us to….The trailing ‹
]› matches a literal]character to end the section header. There’s no need to escape this character with a backslash because it does not occur within a character class.
If you only want to find a specific section header, that’s even
easier. The following regex matches the header for a section called
Section1:
^[Section1]
| Regex options: ^ and $ match at line breaks |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
In this case, the only difference from a plain-text search for
“[Section1]” is that the match must occur at the beginning of a line.
This prevents matching commented-out section headers (preceded by a
semicolon) or what looks like a header but is actually part of a
parameter’s value (e.g., Item1=[Value1]).
Recipe 9.14 describes how to match INI section blocks. Recipe 9.15 does the same for INI name-value pairs.
Techniques used in the regular expressions in this recipe are discussed in Chapter 2. Recipe 2.1 explains which special characters need to be escaped. Recipe 2.2 explains how to match nonprinting characters. Recipe 2.3 explains character classes. Recipe 2.5 explains anchors. Recipe 2.12 explains repetition.
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