ruby - How to match the last occurrence of a pattern?

Ruby - How to match the last occurrence of a pattern?

To match the last occurrence of a pattern in a string using regular expressions in Ruby, you can use a combination of the .* wildcard and a capturing group. Here's an example:

string = "abc def ghi abc jkl mno abc" # Match the last occurrence of "abc" if match = string.match(/.*(\babc\b)/) last_occurrence = match[1] puts "Last occurrence of 'abc': #{last_occurrence}" else puts "Pattern not found" end

In this example:

  • .* matches any character (except for a newline) zero or more times.
  • (\babc\b) is a capturing group that matches the pattern "abc" with word boundaries \b. The capturing group allows us to extract the last occurrence.

The result will be:

Last occurrence of 'abc': abc

Adjust the regular expression pattern based on your specific requirements. If you're dealing with a multiline string, you might want to use the m modifier to make . match newline characters:

if match = string.match(/.*(\babc\b)/m) # ... end

This way, the .* will also match across newline characters.

Examples

  1. "Ruby regex match last occurrence"

    • Code:
      your_string[/your_pattern.*\z/]
    • Description: This code uses the regular expression .*\z to match the last occurrence of the specified pattern in your_string.

  2. "Ruby match last word in a string"

    • Code:
      your_string[/\b\w+\z/]
    • Description: This code uses the regular expression \b\w+\z to match the last word in your_string.

  3. "Ruby match last number in a string"

    • Code:
      your_string[/\d+\z/]
    • Description: This code uses the regular expression \d+\z to match the last number in your_string.

  4. "Ruby match last occurrence before a specific character"

    • Code:
      your_string[/your_pattern(?=[^your_pattern]*\z)/]
    • Description: This code uses a positive lookahead to match the last occurrence of your_pattern before a specific character.

  5. "Ruby match last occurrence case-insensitive"

    • Code:
      your_string[/(?i)your_pattern.*\z/]
    • Description: This code uses (?i) to make the pattern case-insensitive and matches the last occurrence of the specified pattern in your_string.

  6. "Ruby match last occurrence with multiple patterns"

    • Code:
      your_string[/(pattern1|pattern2).*\z/]
    • Description: This code uses a regex with multiple patterns to match the last occurrence of either pattern1 or pattern2 in your_string.

  7. "Ruby match last occurrence of a character"

    • Code:
      your_string[/your_character(?=[^your_character]*\z)/]
    • Description: This code uses a positive lookahead to match the last occurrence of a specific character in your_string.

  8. "Ruby match last occurrence in a multiline string"

    • Code:
      your_string[/(your_pattern).*\z/m]
    • Description: This code uses the m flag to make the regex match across multiple lines and finds the last occurrence of your_pattern in your_string.

  9. "Ruby match last occurrence and capture group"

    • Code:
      your_string[/(your_pattern).*\z/, 1]
    • Description: This code uses a capture group to match and capture the last occurrence of your_pattern in your_string.

  10. "Ruby match last occurrence excluding certain characters"

    • Code:
      your_string[/your_pattern[^\s]*\z/]
    • Description: This code uses a negated character class ([^\s]) to exclude certain characters and match the last occurrence of your_pattern in your_string.

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