[Q] how can I start a shell process and return immediately?

[Stephen Bannasch-3]

I want to start a Java program from a Ruby program and have the Java
program run in another process and have control returned to my Ruby
program as soon as the Java process starts up successfully.

I can do this from a shell by suffixing an '&':

   java -cp <classpath> <main_class>&

starts the Java program in a background process thread and returns
control the shell.

When I try this from a Ruby program the program blocks until the Java
program is terminated.

[7stud --]

Stephen Bannasch wrote:
>
> When I try this from a Ruby program the program blocks until the Java
> program is terminated.
>

"this"?  Here let's play a little game.  You try to help me.   Here is
my question:  I have a for loop that doesn't work.  Can you fix it?

--
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[Cameron Matheson-2]

Hello,

On 9/28/07, Stephen Bannasch <stephen.bannasch@...> wrote:
> I want to start a Java program from a Ruby program and have the Java
> program run in another process and have control returned to my Ruby
> program as soon as the Java process starts up successfully.
>
> When I try this from a Ruby program the program blocks until the Java
> program is terminated.

There may be another way, but the first thing that came to mind for me
was just to launch it in another thread:

Thread.new { `java -cp <classpath> <main_class>` }

Cameron

[Sebastian Hungerecker-2]

Stephen Bannasch wrote:
>    java -cp <classpath> <main_class>&
>
> starts the Java program in a background process thread and returns
> control the shell.
>
> When I try this from a Ruby program the program blocks until the Java
> program is terminated.

I don't know what exactly "this" is, but system("some_command &") works just
fine here.


--
Jabber: sepp2k@...
ICQ: 205544826

[7stud --]

r8test.rb
-------
sleep(4)
puts  "Data from subprocess: 10 20 30"



main_program.rb
--------------
puts "main program"
sleep(1)

pipe = IO.popen("ruby r8test.rb", "w+")

puts "main program executing while subprocess is sleeping"
Process.wait

pipe.close_write
puts pipe.gets

pipe.close_read
--
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[Stephen Bannasch-3]

>Hello,
>
>On 9/28/07, Stephen Bannasch <stephen.bannasch@...> wrote:
>> I want to start a Java program from a Ruby program and have the Java
>> program run in another process and have control returned to my Ruby
>> program as soon as the Java process starts up successfully.
>>
>> When I try this from a Ruby program the program blocks until the Java
>> program is terminated.
>
>There may be another way, but the first thing that came to mind for me
>was just to launch it in another thread:
>
>Thread.new { `java -cp <classpath> <main_class>` }

* Thanks Cameron,

That worked, I hadn't used threads before and they were what I needed.

* Thanks Sebastion,

I thought I had tried this:

  system("some_command&")

and it didn't work -- but it was late and I needed to sleep -- today that works fine -- so obviously I wasn't thinking as clearly as I could have been.

* Thanks 7stud,

IO.popen is interesting, I'm playing with your simple test programs and reading chapter 11 in the Pickaxe book.

[7stud --]

Stephen Bannasch wrote:
>
> * Thanks 7stud,
>
> IO.popen is interesting, I'm playing with your simple test programs and
> reading chapter 11 in the Pickaxe book.

You can consider the sleep(4) statement in the subprocess as a stand in
for some calculation or task that takes 4 seconds to execute.

--
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[Enling Li]

I have another quetion related to fire off a back ground shell process
on a remote Linux.

    require "net/ssh"

    ssh = Net::SSH.start( '10.0.77.87', 'toor',  :password=>'logapp')
    ssh.exec!("/root/test.pl &")
    ssh.close
    puts "I want to be here immediately, but not"

The above code hangs also because test.pl contains a long sleep and do
nothing. Can someone offer me a help?

Thank you in advance.

Enling

Stephen Bannasch wrote:

> I want to start a Java program from a Ruby program and have the Java
> program run in another process and have control returned to my Ruby
> program as soon as the Java process starts up successfully.
>
> I can do this from a shell by suffixing an '&':
>
>    java -cp <classpath> <main_class>&
>
> starts the Java program in a background process thread and returns
> control the shell.
>
> When I try this from a Ruby program the program blocks until the Java
> program is terminated.

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

[Rob Biedenharn-2]

On Jul 9, 2009, at 5:13 PM, Enling Li wrote:

> I have another quetion related to fire off a back ground shell process
> on a remote Linux.
>
>    require "net/ssh"
>
>    ssh = Net::SSH.start( '10.0.77.87', 'toor',  :password=>'logapp')
>    ssh.exec!("/root/test.pl &")
>    ssh.close
>    puts "I want to be here immediately, but not"
>
> The above code hangs also because test.pl contains a long sleep and do
> nothing. Can someone offer me a help?
>
> Thank you in advance.
>
> Enling
>
> Stephen Bannasch wrote:
>> I want to start a Java program from a Ruby program and have the Java
>> program run in another process and have control returned to my Ruby
>> program as soon as the Java process starts up successfully.
>>
>> I can do this from a shell by suffixing an '&':
>>
>>   java -cp <classpath> <main_class>&
>>
>> starts the Java program in a background process thread and returns
>> control the shell.
>>
>> When I try this from a Ruby program the program blocks until the Java
>> program is terminated.

If your system has the `setsid` (set session id) program (and the  
underlying system call), then you could try:

   ssh.exec!("setsid /root/test.pl")

or

   setsid java -cp YOURCLASSPATH MainClass

but you may wish to redirect output.

   ssh.exec!("setsid /root/test.pl >/tmp/test.log 2>&1")

-Rob

Rob Biedenharn http://agileconsultingllc.com
Rob@...

[Enling Li]

Thank you, Rob for the quick reply and help. I tried the commmand you
enclosed in the mail. It did not work out. I still got hang at the
exec() command.

Here are the options I did. They behave the same. They don't work. By
the way, my linux system has setsid().

ssh.exec!("setsid /root/test.pl >/tmp/test.log 2>&1")
ssh.exec!("setsid /root/test.pl > /dev/null 2>&1")
ssh.exec!("setsid /root/test.pl")

Thanks.

Enling


Rob Biedenharn wrote:

> On Jul 9, 2009, at 5:13 PM, Enling Li wrote:
>
>> The above code hangs also because test.pl contains a long sleep and do
>>>
>>> I can do this from a shell by suffixing an '&':
>>>
>>>   java -cp <classpath> <main_class>&
>>>
>>> starts the Java program in a background process thread and returns
>>> control the shell.
>>>
>>> When I try this from a Ruby program the program blocks until the Java
>>> program is terminated.
>
> If your system has the `setsid` (set session id) program (and the
> underlying system call), then you could try:
>
>    ssh.exec!("setsid /root/test.pl")
>
> or
>
>    setsid java -cp YOURCLASSPATH MainClass
>
> but you may wish to redirect output.
>
>    ssh.exec!("setsid /root/test.pl >/tmp/test.log 2>&1")
>
> -Rob
>
> Rob Biedenharn    http://agileconsultingllc.com
> Rob@...

--
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[John W Higgins]

On Thu, Jul 9, 2009 at 4:53 PM, Enling Li <enling.li@...> wrote:

> Thank you, Rob for the quick reply and help. I tried the commmand you
> enclosed in the mail. It did not work out. I still got hang at the
> exec() command.
>
> Here are the options I did. They behave the same. They don't work. By
> the way, my linux system has setsid().
>
> ssh.exec!("setsid /root/test.pl >/tmp/test.log 2>&1")
> ssh.exec!("setsid /root/test.pl > /dev/null 2>&1")
> ssh.exec!("setsid /root/test.pl")
>

Would just dropping the ssh section into it's own thread accomplish your
task? That seems like a rather simple way of getting what you want.

John

[Enling Li]

I tried that before. The thread won't solve the issue because once child
thread established it does the same way as main tread. When the main
thread terminates, the child gets killed also. It ends up nothing
happened to the shell command.

Thanks.

Enling

John W Higgins wrote:
> On Thu, Jul 9, 2009 at 4:53 PM, Enling Li <enling.li@...>
> wrote:
>
>>
> Would just dropping the ssh section into it's own thread accomplish your
> task? That seems like a rather simple way of getting what you want.
>
> John

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[Rob Biedenharn-2]

On Jul 9, 2009, at 7:53 PM, Enling Li wrote:

> Thank you, Rob for the quick reply and help. I tried the commmand you
> enclosed in the mail. It did not work out. I still got hang at the
> exec() command.
>
> Here are the options I did. They behave the same. They don't work. By
> the way, my linux system has setsid().
>
> ssh.exec!("setsid /root/test.pl >/tmp/test.log 2>&1")
> ssh.exec!("setsid /root/test.pl > /dev/null 2>&1")
> ssh.exec!("setsid /root/test.pl")
>
> Thanks.
>
> Enling

OK, what about:

ssh.exec!("sh -c 'setsid /root/test.pl > /dev/null 2>&1'")

or perhaps bash, /bin/sh, or /bin/bash in place of sh

Of course, I'm assuming that you are verifying that you can ssh  
manually and run these commands yourself. (If not, get to a command  
that works even after you log out manually.)

-Rob

> Rob Biedenharn wrote:
>> On Jul 9, 2009, at 5:13 PM, Enling Li wrote:
>>
>>> The above code hangs also because test.pl contains a long sleep  
>>> and do
>>>>
>>>> I can do this from a shell by suffixing an '&':
>>>>
>>>>  java -cp <classpath> <main_class>&
>>>>
>>>> starts the Java program in a background process thread and returns
>>>> control the shell.
>>>>
>>>> When I try this from a Ruby program the program blocks until the  
>>>> Java
>>>> program is terminated.
>>
>> If your system has the `setsid` (set session id) program (and the
>> underlying system call), then you could try:
>>
>>   ssh.exec!("setsid /root/test.pl")
>>
>> or
>>
>>   setsid java -cp YOURCLASSPATH MainClass
>>
>> but you may wish to redirect output.
>>
>>   ssh.exec!("setsid /root/test.pl >/tmp/test.log 2>&1")
>>
>> -Rob
>>
>> Rob Biedenharn    http://agileconsultingllc.com
>> Rob@...
>
> --
> Posted via http://www.ruby-forum.com/.
>

[John W Higgins]

Are you sure you are properly connecting to the server? Have you tried just
running something like ls and getting back a result? I just tried running a
simple script that sleeps for 100 seconds and it ran just fine after the
remote app was finished.

If that still leaves you in trouble - you might want to look into Screen
which is designed to run apps detached from the login shell so that would
certainly be of use if needed. This is the command I use to run an app
detached - screen -D -m command.rb

John


On Thu, Jul 9, 2009 at 6:34 PM, Enling Li <enling.li@...> wrote:

> I tried that before. The thread won't solve the issue because once child
> thread established it does the same way as main tread. When the main
> thread terminates, the child gets killed also. It ends up nothing
> happened to the shell command.
>
> Thanks.
>
> Enling
>
> John W Higgins wrote:
> > On Thu, Jul 9, 2009 at 4:53 PM, Enling Li <enling.li@...>
> > wrote:
> >
> >>
> > Would just dropping the ssh section into it's own thread accomplish your
> > task? That seems like a rather simple way of getting what you want.
> >
> > John
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

[Enling Li]

John,

The key is I don't want to wait for the remote to finish. If I wait for
remote to complete, I don't have problem.

Thanks.

Enling


John W Higgins wrote:

> Are you sure you are properly connecting to the server? Have you tried
> just
> running something like ls and getting back a result? I just tried
> running a
> simple script that sleeps for 100 seconds and it ran just fine after the
> remote app was finished.
>
> If that still leaves you in trouble - you might want to look into Screen
> which is designed to run apps detached from the login shell so that
> would
> certainly be of use if needed. This is the command I use to run an app
> detached - screen -D -m command.rb
>
> John

--
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[Enling Li]

Rob,

That does not work either. I tried from shell befreo running the ruby
script remotely.

ssh.exec!("/bin/bash -c /usr/bin/setsid /usr/bin/perl /root/test.pl")
ssh.exec!("/bin/bash /usr/bin/setsid /usr/bin/perl /root/test.pl")
ssh.exec!("/bin/bash /usr/bin/setsid /root/test.pl")

They just don't work from ruby Net::SSH

Thanks.

Enling
Rob Biedenharn wrote:

> On Jul 9, 2009, at 7:53 PM, Enling Li wrote:
>
>>
>> Thanks.
>>
>> Enling
>
> OK, what about:
>
> ssh.exec!("sh -c 'setsid /root/test.pl > /dev/null 2>&1'")
>
> or perhaps bash, /bin/sh, or /bin/bash in place of sh
>
> Of course, I'm assuming that you are verifying that you can ssh
> manually and run these commands yourself. (If not, get to a command
> that works even after you log out manually.)
>
> -Rob

--
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[John W Higgins]

Enling,

On Thu, Jul 9, 2009 at 8:06 PM, Enling Li <enling.li@...> wrote:

> John,
>
> The key is I don't want to wait for the remote to finish. If I wait for
> remote to complete, I don't have problem.
>

Sorry I used the wrong wording - I meant that Machine A connected to Machine
B using Net::SSH and ran a script that slept for 100 seconds. Machine A then
disconnected without blocking and Machine B continued to execute the script
that was sleeping away. Again make sure you are connecting because you could
easily be not getting to the server at all - the block could just as easily
be a connection block and not an execution block. And if you are connecting
and still for some reason blocking - Screen is definitely the answer because
that is exactly what is it designed for.

John

> Thanks.
>
> Enling
>
>
> John W Higgins wrote:
> > Are you sure you are properly connecting to the server? Have you tried
> > just
> > running something like ls and getting back a result? I just tried
> > running a
> > simple script that sleeps for 100 seconds and it ran just fine after the
> > remote app was finished.
> >
> > If that still leaves you in trouble - you might want to look into Screen
> > which is designed to run apps detached from the login shell so that
> > would
> > certainly be of use if needed. This is the command I use to run an app
> > detached - screen -D -m command.rb
> >
> > John
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

[Andrew Kaspick]

Enling Li wrote:

> I have another quetion related to fire off a back ground shell process
> on a remote Linux.
>
>     require "net/ssh"
>
>     ssh = Net::SSH.start( '10.0.77.87', 'toor',  :password=>'logapp')
>     ssh.exec!("/root/test.pl &")
>     ssh.close
>     puts "I want to be here immediately, but not"
>
> The above code hangs also because test.pl contains a long sleep and do
> nothing. Can someone offer me a help?
>
> Thank you in advance.
>
> Enling

I run long running remote tasks that return immediately with...

ssh.exec!("nohup /root/test.pl >/tmp/test.log 2>&1 &")
--
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[Enling Li]

Andrew,

That is excellent. It resolved the issue.
Thank you very much.

Enling


Andrew Kaspick wrote:

> Enling Li wrote:
>> I have another quetion related to fire off a back ground shell process
>> on a remote Linux.
>>
>>     require "net/ssh"
>>
>>     ssh = Net::SSH.start( '10.0.77.87', 'toor',  :password=>'logapp')
>>     ssh.exec!("/root/test.pl &")
>>     ssh.close
>>     puts "I want to be here immediately, but not"
>>
>> The above code hangs also because test.pl contains a long sleep and do
>> nothing. Can someone offer me a help?
>>
>> Thank you in advance.
>>
>> Enling
>
> I run long running remote tasks that return immediately with...
>
> ssh.exec!("nohup /root/test.pl >/tmp/test.log 2>&1 &")

--
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