shelljoin

Builds a command line string from an argument list array joining all elements escaped for Bourne shell and separated by a space.

open('|' + Shellwords.join(['grep', pattern, *files])) { |pipe|
  # ...
}

Array#shelljoin is a shorthand for this function.

open('|' + ['grep', pattern, *files].shelljoin) { |pipe|
  # ...
}