Find a numeric sequence of a specific length in a string in Ruby -


i need able extract sequence of 8 digits given string. sequence not located in same place string string, , may consist of 8 digits.

examples of strings extracted from:

"123 abcdef 12345678 ghijklmn" "12345678 abcd 1234 efghijkl" "123 4567 12345678"

in each of strings above, need 12345678.

i've tried matching regular expression /\d+/, if number appears before 12345678, doesn't work.

you can following regex:

r = /     (?<!\d) # negative lookbehind: cannot match digit     \d{8} # match 8 digits     (?!\d) # negative lookahead: cannot match digit     /x   "12345678 abcd 1234 efghijkl"[r]    #=> "12345678"  "x123456789 abcd 1234 efghijkl"[r]    #=> nil

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