[ANN] open4-0.6.0

Discussion in 'Ruby' started by ara.t.howard@noaa.gov, Aug 31, 2006.

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    URIS

    http://rubyforge.org/projects/codeforpeople/
    http://www.codeforpeople.com/lib/ruby/

    SYNOPSIS

    open child process with handles on pid, stdin, stdout, and stderr: manage
    child processes and their io handles easily.

    HISTORY

    0.6.0:
    - added feature for exitstatus to be list of acceptable exit statuses

    Open4.spawn 'ruby -e "exit 42"' # raises
    Open4.spawn 'ruby -e "exit 42"', :exitstatus=>[0,42] # ok

    - added :status switch, which will always simply return the status (no
    error thrown for failure)

    Open4.spawn 'ruby -e "exit 42"' # raises
    status = Open4.spawn 'ruby -e "exit 42"', :status=>true # ok

    note, however, that any SpawnError does in fact contain the failed
    status so, even when they are thrown, error status can be retrieved:

    include Open4

    status =
    begin
    spawn 'ruby -e "exit 42"'
    rescue SpawnError => e
    warn{ e }
    e.status
    end

    0.5.1:
    - fixes a __critical__ but in ThreadEnsemble class that had a race
    condition that could cause thread deadlock. sorry bout that folks.

    0.5.0:
    - on the suggestion of tim pease (thanks tim!), i added timeout features
    to open4. the command run may have an overall timeout and individual
    timeouts set for each of the io handles. for example

    cmd = 'command_that_produce_out_at_one_second_intervals'

    open4.spawn cmd, :stdout_timeout => 2

    or

    cmd = 'command_that_should_complete_in_about_one_minute'

    open4.spawn cmd, :timeout => 60

    or

    cmd = 'consumes_input_at_one_line_per_second_rate'

    input = %w( 42 forty-two 42.0 )

    open4.spawn cmd, :stdin=>input, :stdin_timeout=>1

    - added 'open4' alias so one can write

    open4.spawn vs Open4.spawn

    or even

    open4(cmd) do |pid,i,o,e|
    end

    - added signal info to SpawnError

    0.4.0:
    - improved error handling contributed by jordan breeding.
    - introduction of background/bg method

    0.3.0 :
    - bug fix from jordan breeding. general clean up. added spawn method.

    0.2.0 :
    - added exception marshaled from child -> parent when exec fails. thanks
    to jordan breeding for a patch (yay!) and paul brannan for this most
    excellent idea.

    0.1.0 :
    - fixed docs to correctly show return value of popen4 (pid first not last).
    thanks Stefanie Tellex <> for catching this.
    0.0.0 :
    - initial version

    INSTALL

    ~> gem install open4

    SAMPLES

    ----------------------------------------------------------------------------
    simple usage
    ----------------------------------------------------------------------------

    harp: > cat sample/simple.rb
    require "open4"

    pid, stdin, stdout, stderr = Open4::popen4 "sh"

    stdin.puts "echo 42.out"
    stdin.puts "echo 42.err 1>&2"
    stdin.close

    ignored, status = Process::waitpid2 pid

    puts "pid : #{ pid }"
    puts "stdout : #{ stdout.read.strip }"
    puts "stderr : #{ stderr.read.strip }"
    puts "status : #{ status.inspect }"
    puts "exitstatus : #{ status.exitstatus }"


    harp: > ruby sample/simple.rb
    pid : 17273
    stdout : 42.out
    stderr : 42.err
    status : #<Process::Status: pid=17273,exited(0)>
    exitstatus : 0


    ----------------------------------------------------------------------------
    in block form - the child process is automatically waited for
    ----------------------------------------------------------------------------

    harp: > cat sample/block.rb
    require 'open4'

    status =
    Open4::popen4("sh") do |pid, stdin, stdout, stderr|
    stdin.puts "echo 42.out"
    stdin.puts "echo 42.err 1>&2"
    stdin.close

    puts "pid : #{ pid }"
    puts "stdout : #{ stdout.read.strip }"
    puts "stderr : #{ stderr.read.strip }"
    end

    puts "status : #{ status.inspect }"
    puts "exitstatus : #{ status.exitstatus }"


    harp: > ruby sample/block.rb
    pid : 17295
    stdout : 42.out
    stderr : 42.err
    status : #<Process::Status: pid=17295,exited(0)>
    exitstatus : 0

    ----------------------------------------------------------------------------
    exceptions are marshaled from child to parent if fork/exec fails
    ----------------------------------------------------------------------------

    harp: > cat sample/exception.rb
    require "open4"
    Open4::popen4 "noexist"


    harp: > ruby sample/exception.rb
    /dmsp/reference/ruby-1.8.1//lib/ruby/site_ruby/open4.rb:100:in `popen4': No such file or directory - noexist (Errno::ENOENT)
    from sample/exception.rb:3

    ----------------------------------------------------------------------------
    the spawn method provides and even more convenient method of running a
    process, allowing any object that supports 'each', 'read', or 'to_s' to be
    given as stdin and any objects that support '<<' to be given as
    stdout/stderr. an exception is thrown if the exec'd cmd fails (nonzero
    exitstatus) unless the option 'raise'=>false is given
    ----------------------------------------------------------------------------

    harp: > cat sample/spawn.rb
    require 'open4'
    include Open4

    cat = ' ruby -e" ARGF.each{|line| STDOUT << line} " '

    stdout, stderr = '', ''
    status = spawn cat, 'stdin' => '42', 'stdout' => stdout, 'stderr' => stderr
    p status
    p stdout
    p stderr

    stdout, stderr = '', ''
    status = spawn cat, 0=>'42', 1=>stdout, 2=>stderr
    p status
    p stdout
    p stderr


    harp: > RUBYLIB=lib ruby sample/spawn.rb
    0
    "42"
    ""
    0
    "42"
    ""


    ----------------------------------------------------------------------------
    the bg/background method is similar to spawn, but the process is
    automatically set running in a thread. the returned thread has several
    methods added dynamically which return the pid and blocking calls to the
    exitstatus.
    ----------------------------------------------------------------------------

    harp: > cat sample/bg.rb
    require 'yaml'
    require 'open4'
    include Open4

    stdin = '42'
    stdout = ''
    stderr = ''

    t = bg 'ruby -e"sleep 4; puts ARGF.read"', 0=>stdin, 1=>stdout, 2=>stderr

    waiter = Thread.new{ y t.pid => t.exitstatus } # t.exitstatus is a blocking call!

    while((status = t.status))
    y "status" => status
    sleep 1
    end

    waiter.join

    y "stdout" => stdout


    harp: > ruby sample/bg.rb
    ---
    status: run
    ---
    status: sleep
    ---
    status: sleep
    ---
    status: sleep
    ---
    21357: 0
    ---
    stdout: "42\n"

    ----------------------------------------------------------------------------
    the timeout methods can be used to ensure execution is preceding at the
    desired interval. note also how to setup a 'pipeline'
    ----------------------------------------------------------------------------

    harp: > cat sample/stdin_timeout.rb
    require 'open4'

    producer = 'ruby -e" STDOUT.sync = true; loop{sleep(rand+rand) and puts 42} "'

    consumer = 'ruby -e" STDOUT.sync = true; STDIN.each{|line| puts line} "'

    open4(producer) do |pid, i, o, e|

    open4.spawn consumer, :stdin=>o, :stdout=>STDOUT, :stdin_timeout => 1.4

    end


    harp: > ruby sample/stdin_timeout.rb
    42
    42
    42
    42
    42
    /dmsp/reference/ruby-1.8.1//lib/ruby/1.8/timeout.rb:42:in `relay': execution expired (Timeout::Error)

    AUTHOR



    LICENSE

    ruby's


    enjoy.

    -a
    --
    what science finds to be nonexistent, we must accept as nonexistent; but what
    science merely does not find is a completely different matter... it is quite
    clear that there are many, many mysterious things.
    - h.h. the 14th dalai lama
     
    , Aug 31, 2006
    #1
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