# Net::SSH performance question

**URL:** <https://www.ruby-forum.com/t/net-ssh-performance-question/103555>\
**Category:** Ruby\
**Created:** [May 7, 2007, 9:18pm UTC](https://www.ruby-forum.com/t/net-ssh-performance-question/103555 "2007-05-07T21:18:55Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![knohr](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@knohr](https://www.ruby-forum.com/u/knohr)\
**Post date:** [May 7, 2007, 9:18pm UTC](https://www.ruby-forum.com/t/net-ssh-performance-question/103555/1 "2007-05-07T21:18:55Z")

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I am using Net::SSH to execute scripts on a remote server. The script  
that it executes takes a long time to complete, and dumps allot of  
stuff to stdout. If i allow the script to run as is, this causes ruby  
(on the local machine) to eat up massive amounts of cycles, as it  
parses the stdout. Redirecting the stdout to /dev/null on the remote  
box will fix the performance issue, but will cause me to lose my SSH  
session due to inactivity.

Is there is a way to optimize the following code, (maybe having STDOUT  
have a low buffer size)?  
keep in mind:  
A: i need ssh session to be persistent  
B: i cannot modify the settings on the server  
C: i really don’t want to rewrite the perl script _~2000 lines_  
D: i would prefer that the script does not move past the shell.perl  
line until the script has completed on the remote box.

Net::SSH.start(‘foo’, :username=\>‘bar’, :password=\>’’) do |session|  
copy\_file(session, ‘/tmp/file’)  
shell = session.shell.sync  
shell.mv ("/tmp/file .")  
shell.perl “test”  
puts “done”  
end

---

<div class="post-metadata">

**Author:** ![knohr](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/ecd19e/32.png) [@knohr](https://www.ruby-forum.com/u/knohr)\
**Post date:** [May 7, 2007, 11:49pm UTC](https://www.ruby-forum.com/t/net-ssh-performance-question/103555/2 "2007-05-07T23:49:17Z")

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On 5/7/07, knohr [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> keep in mind:  
> shell.mv (“/tmp/file .”)  
> shell.perl “test”  
> puts “done”  
> end

Hmm there is one question I would have? What do you need as  
result/output, if I understood correctly nothing?  
In that case maybe not using shell should help, the following works  
perfectly on my box

Net::SSH.start( ‘localhost’ ) do |session|  
session.open\_channel do | channel |  
channel.on\_data do | ch, data |  
puts data  
end  
channel.exec “find /home/robert -exec ls -ltr {} \; \>/dev/null”  
end  
session.loop  
end

It waits until the channel is closed.

HTH  
Robert