Flowdock
foreach(p1, p2 = v2, p3 = v3, p4 = v4) public

Executes the block for every line in the named I/O port, where lines are separated by sep.

If no block is given, an enumerator is returned instead.

IO.foreach("testfile") {|x| print "GOT ", x }

produces:

GOT This is line one
GOT This is line two
GOT This is line three
GOT And so on...

If the last argument is a hash, it’s the keyword argument to open. See IO.read for detail.

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March 19, 2015
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enumerator and number of lines to read

Example

File.foreach(filename)
  .take(number_of_lines)
  .map do |line|
    # ... stuff ... 
end