Fork on Windows

What's the best way to see if a particular platform supports fork? I
know I could check if it's running on Windows, but I'd like something
more direct (and presumably accurate).

A similar question: assuming a standard Ruby install (that is, no
popen4), what's the most robust way of running a shell command and
capturing STDOUT and STDERR?
`command 2>&1` seems to not always work on Windows.

···

--
Posted via http://www.ruby-forum.com/.

What's the best way to see if a particular platform supports fork? I
know I could check if it's running on Windows, but I'd like something
more direct (and presumably accurate).

You could test fork and see if you get a defined value back.

A similar question: assuming a standard Ruby install (that is, no
popen4), what's the most robust way of running a shell command and
capturing STDOUT and STDERR?
`command 2>&1` seems to not always work on Windows.

And it won't. That's bourne-shell syntax.

http://www.ruby-doc.org/stdlib/libdoc/open3/rdoc/index.html

Mike

···

On 1/1/07, Robert James <srobertjames@gmail.com> wrote:

What's the best way to see if a particular platform supports fork? I
know I could check if it's running on Windows, but I'd like something
more direct (and presumably accurate).

has_fork =
   begin
     fork{ exit }
     Process.wait
     true
   rescue
     false
   end

A similar question: assuming a standard Ruby install (that is, no
popen4), what's the most robust way of running a shell command and
capturing STDOUT and STDERR?
`command 2>&1` seems to not always work on Windows.

NAME

   systemu.rb

SYNOPSIS

   univeral capture of stdout and stderr and handling of child process pid for windows, *nix, etc.

URIS

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

INSTALL

   gem install systemu

SAMPLES

   <========< samples/a.rb >========>

   ~ > cat samples/a.rb

···

On Tue, 2 Jan 2007, Robert James wrote:

     #
     # systemu can be used on any platform to return status, stdout, and stderr of
     # any command. unlike other methods like open3/popen4 there is zero danger of
     # full pipes or threading issues hanging your process or subprocess.
     #
       require 'systemu'

       date = %q( ruby -e" t = Time.now; STDOUT.puts t; STDERR.puts t " )

       status, stdout, stderr = systemu date
       p [ status, stdout, stderr ]

   ~ > ruby samples/a.rb

     [#<Process::Status: pid=9960,exited(0)>, "Fri Nov 03 17:22:23 MST 2006\n", "Fri Nov 03 17:22:23 MST 2006\n"]

   <========< samples/b.rb >========>

   ~ > cat samples/b.rb

     #
     # quite a few keys can be passed to the command to alter it's behaviour. if
     # either stdout or stderr is supplied those objects should respond_to? '<<'
     # and only status will be returned
     #
       require 'systemu'

       date = %q( ruby -e" t = Time.now; STDOUT.puts t; STDERR.puts t " )

       stdout, stderr = '', ''
       status = systemu date, 'stdout' => stdout, 'stderr' => stderr
       p [ status, stdout, stderr ]

   ~ > ruby samples/b.rb

     [#<Process::Status: pid=9965,exited(0)>, "Fri Nov 03 17:22:23 MST 2006\n", "Fri Nov 03 17:22:23 MST 2006\n"]

   <========< samples/c.rb >========>

   ~ > cat samples/c.rb

     #
     # of course stdin can be supplied too. synonyms for 'stdin' include '0' and
     # 0. the other stdio streams have similar shortcuts
     #
       require 'systemu'

       cat = %q( ruby -e" ARGF.each{|line| puts line} " )

       status = systemu cat, 0=>'the stdin for cat', 1=>stdout=''
       puts stdout

   ~ > ruby samples/c.rb

     the stdin for cat

   <========< samples/d.rb >========>

   ~ > cat samples/d.rb

     #
     # the cwd can be supplied
     #
       require 'systemu'
       require 'tmpdir'

       pwd = %q( ruby -e" STDERR.puts Dir.pwd " )

       status = systemu pwd, 2=>(stderr=''), :cwd=>Dir.tmpdir
       puts stderr

   ~ > ruby samples/d.rb

     /tmp

   <========< samples/e.rb >========>

   ~ > cat samples/e.rb

     #
     # any environment vars specified are merged into the child's environment
     #
       require 'systemu'

       env = %q( ruby -r yaml -e" puts ENV[ 'answer' ] " )

       status = systemu env, 1=>stdout='', 'env'=>{ 'answer' => 0b101010 }
       puts stdout

   ~ > ruby samples/e.rb

     42

   <========< samples/f.rb >========>

   ~ > cat samples/f.rb

     #
     # if a block is specified then it is passed the child pid and run in a
     # background thread. note that this thread will __not__ be blocked during the
     # execution of the command so it may do useful work such as killing the child
     # if execution time passes a certain threshold
     #
       require 'systemu'

       looper = %q( ruby -e" loop{ STDERR.puts Time.now.to_i; sleep 1 } " )

       status, stdout, stderr =
         systemu looper do |cid|
           sleep 3
           Process.kill 9, cid
         end

       p [ status, stdout, stderr ]

   ~ > ruby samples/f.rb

     [#<Process::Status: pid=9985,signaled(SIGKILL=9)>, "", "1162599744\n1162599745\n1162599746\n1162599747\n"]

-a
--
if you find yourself slandering anybody, first imagine that your mouth is
filled with excrement. it will break you of the habit quickly enough. - the
dalai lama

Michael P. Soulier wrote:

You could test fork and see if you get a defined value back.

Not sure how to do this... Kernel.respond_to? :fork is true on both
platforms.

···

--
Posted via http://www.ruby-forum.com/\.

It's also cmd.exe syntax, so it /should/ work in Windows, too.

http://www.microsoft.com/technet/archive/winntas/deploy/prodspecs/shellscr.mspx?mfr=true

TomP

···

On Jan 1, 2007, at 6:28 PM, Michael P. Soulier wrote:

On 1/1/07, Robert James <srobertjames@gmail.com> wrote:

A similar question: assuming a standard Ruby install (that is, no
popen4), what's the most robust way of running a shell command and
capturing STDOUT and STDERR?
`command 2>&1` seems to not always work on Windows.

And it won't. That's bourne-shell syntax.

Not sure how to do this... Kernel.respond_to? :fork is true on both
platforms.

can you execute fork in windows and catch the exception if it fails ?

···

--
best,
                        UG
---
Uma Geller

I've found that on winblows, one must invoke cme.exe /c "command" to
get redirection to work properly.

Mike

···

On 1/2/07, Tom Pollard <tomp@earthlink.net> wrote:

> And it won't. That's bourne-shell syntax.

It's also cmd.exe syntax, so it /should/ work in Windows, too.

http://www.microsoft.com/technet/archive/winntas/deploy/prodspecs/
shellscr.mspx?mfr=true

--
Michael P. Soulier <msoulier@digitaltorque.ca>
"Any intelligent fool can make things bigger and more complex... It takes a
touch of genius - and a lot of courage to move in the opposite direction."
--Albert Einstein

Uma Geller wrote:

can you execute fork in windows and catch the exception if it fails ?

Nope - fork is used deep inside a lib. I'd like to exit right away if
the platform doesn't support it, otherwise let the lib run as normal.

···

--
Posted via http://www.ruby-forum.com/\.

Uma Geller wrote:

Not sure how to do this... Kernel.respond_to? :fork is true on both
platforms.

can you execute fork in windows and catch the exception if it fails ?

Is this like "stick a fork in it and see if it's done?"

<ducking>

···

--
M. Edward (Ed) Borasky, FBG, AB, PTA, PGS, MS, MNLP, NST, ACMC(P)
http://borasky-research.blogspot.com/

If God had meant for carrots to be eaten cooked, He would have given rabbits fire.

Nope - fork is used deep inside a lib. I'd like to exit right away if
the platform doesn't support it, otherwise let the lib run as normal.

then do this exception test during the installation process

···

--
best,
                        UG
---
Uma Geller