Testing Open3.capture3 in Ruby, using array-style command syntax vs. string-style command syntax with Unix-style pipes

capture3_test.rb

require 'open3'

cli_pipe_test_array = [
  "echo",
  '{"some": "json", "data": 345, "here": true}',
  "|",
  "jq",
  '".data"',
  "|",
  "xargs",
  "echo"
]
cli_pipe_test_string = %Q@echo '{"some": "json", "data": 345, "here": true}' | jq ".data" | xargs echo@

# customize the environment variables passed to the worker container
def spawn_env(custom_env = {})
  env_vars = {}
  env_vars.merge(custom_env)
end

# `capture3` supports a hash of options to specify process attributes
# see Process.spawn http://ruby-doc.org/core-2.5.1/Process.html#method-c-spawn
# for available options.
# override this method to suite your needs
def spawn_attributes
  {}
end

[cli_pipe_test_array, cli_pipe_test_string].each do |cli_pipe_test|
  stdout, stderr, status = Open3.capture3(
    spawn_env,
    *cli_pipe_test,
    spawn_attributes
  )

  p ""
  p "COMMAND:"
  p cli_pipe_test
  p ""
  p "STDOUT:"
  p stdout
  p ""
  p "STDERR:"
  p stderr
  p ""
  p "STATUS:", status
end

output

$ ruby capture3_test.rb
""
"COMMAND:"
["echo", "{\"some\": \"json\", \"data\": 345, \"here\": true}", "|", "jq", "\".data\"", "|", "xargs", "echo"]
""
"STDOUT:"
"{\"some\": \"json\", \"data\": 345, \"here\": true} | jq \".data\" | xargs echo\n"
""
"STDERR:"
""
""
"STATUS:"
#<Process::Status: pid 75814 exit 0>
""
"COMMAND:"
"echo '{\"some\": \"json\", \"data\": 345, \"here\": true}' | jq \".data\" | xargs echo"
""
"STDOUT:"
"345\n"
""
"STDERR:"
""
""
"STATUS:"
#<Process::Status: pid 75815 exit 0>