URIS
http://rubyforge.org/frs/?group_id=1024
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
0.5.1:
- fixes a __critical__ but in ThreadEnsemble class that had a race
condition that could cause thread deadlock. sorry bout that folks.
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@noaa.gov
LICENSE
ruby''s
-a
--
to foster inner awareness, introspection, and reasoning is more efficient than
meditation and prayer.
- h.h. the 14th dali lama
