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If I were to be asked what is faster, regular sub string operation or a regular expression, I would without hesitation answer that sub string is.

This was the assumption that I approached a simple task with – stripping slashes from beginning and end of a string. Here’s the code:

path = path[1..-1] if path[0, 1] == '/'
path = path[0..-2] if path[-1, 1] == '/'

I would naturally assume that the block above would be faster than path.gsub!(/^\/|\/$/, ''). But just in case, lets benchmark to be sure.

require 'benchmark'

original = '/hello/somewhat/long/path/here/'
max = 1_000_000

puts Benchmark.measure {
  1.upto(max) do
    path = original
    path = path[1..-1] if path[0, 1] == '/'
    path = path[0..-2] if path[-1, 1] == '/'
  end
}

puts Benchmark.measure {
  1.upto(max) do
    path = original
    path.gsub!(/^/|/$/, '')
  end
}

# prints out
  4.212000   0.000000   4.212000 (  4.270000)
  2.418000   0.000000   2.418000 (  2.435000)

I don’t understand why, but gsub is 57% faster. I find it hard to believe that a few extra Ruby statements introduce so much overhead that it becomes slower than entire regular expressions engine. Anyone has any explanation for this?