Asp Forum - [ANN] open4-0.9.4

ara.t.howard

7/12/2007 5:56:00 AM

URIS

http://rubyforge.org/projects/code...
http://www.codeforpeople.com...

SYNOPSIS

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

HISTORY

0.9.4:
- patch to #background from Corey Jewett

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

ara.t.howard@gmail.com

LICENSE

ruby's

-a
--
we can deny everything, except that we have the possibility of being
better. simply reflect on that.
h.h. the 14th dalai lama

comp.lang.ruby

[ANN] open4-0.9.4

ara.t.howard

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