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End of Life Ruby 3.2 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →

instance method

MatchData#begin

begin(n) → integer
begin(name) → integer

Returns the offset (in characters) of the beginning of the specified match.

When non-negative integer argument n is given, returns the offset of the beginning of the nth match:

Example
m = /(.)(.)(\d+)(\d)/.match("THX1138.")
# => #<MatchData "HX1138" 1:"H" 2:"X" 3:"113" 4:"8">
m[0]       # => "HX1138"
m.begin(0) # => 1
m[3]       # => "113"
m.begin(3) # => 3

m = /(т)(е)(с)/.match('тест')
# => #<MatchData "тес" 1:"т" 2:"е" 3:"с">
m[0]       # => "тес"
m.begin(0) # => 0
m[3]       # => "с"
m.begin(3) # => 2

When string or symbol argument name is given, returns the offset of the beginning for the named match:

Example
m = /(?<foo>.)(.)(?<bar>.)/.match("hoge")
# => #<MatchData "hog" foo:"h" bar:"g">
m[:foo]        # => "h"
m.begin('foo') # => 0
m[:bar]        # => "g"
m.begin(:bar)  # => 2

Related: MatchData#end, MatchData#offset, MatchData#byteoffset.

See also #[] #byteoffset #== #captures also in 4.1 · 4.0 · 3.4 · 3.3 · 3.1 · 3.0