stdlib_libraries/open3_streams.rb

tests/_examples/stdlib_libraries/open3_streams.rb in the metorex repository.

require "open3"

# `popen3` joins the command's three streams to pipes, and its thread names
# the command and answers the status it ended with.
Open3.popen3 "cat; echo err 1>&2" do |input, output, errors, waiter|
  input.write "to the command"
  input.close
  p output.read
  p errors.read
  p waiter.pid.is_a?(Integer)
  p waiter.value.success?
end

# The capturing forms hand the command what it is to read.
p Open3.capture2("tr a-z A-Z", stdin_data: "shout")[0]
out, err, status = Open3.capture3("cat; exit 4", stdin_data: "kept")
p [out, err, status.exitstatus]
p Open3.capture2e("echo out; echo err 1>&2")[0].split.sort

# A pipeline joins each command's output to the next one's input.
p Open3.pipeline("printf 'b\na\n'", "sort").map(&:success?)
Open3.pipeline_r "printf 'x\ny\n'", "wc -l" do |last, waiters|
  p last.read.strip
  p waiters.length
end
Open3.pipeline_rw "sort", "head -1" do |first, last, _|
  first.puts "zebra", "apple"
  first.close
  p last.read
end

Output:

"to the command"
"err\n"
true
true
"SHOUT"
["kept", "", 4]
["err", "out"]
a
b
[true, true]
"2"
2
"apple\n"