# Backticks asynchronous?

**URL:** <https://www.ruby-forum.com/t/backticks-asynchronous/76543>\
**Category:** Ruby\
**Created:** [November 20, 2006, 2:45pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543 "2006-11-20T14:45:56Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [November 20, 2006, 2:45pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543/1 "2006-11-20T14:45:56Z")

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sorry, dumb question possibly, I just want to make sure. if I call  
some Unix command using backticks, that invokes the command, launches  
a new process, and waits until that process terminates before resuming  
program execution, right? especially if I do this:

shell\_output = `some process`

which should capture the output of the process. right? it isn’t possible  
to say

shell\_output = `some process`

and accidentally see execution fork, is it?

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**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [November 20, 2006, 2:45pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543/2 "2006-11-20T14:45:57Z")

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On Mon, Nov 20, 2006 at 08:05:45AM +0900, Giles B. wrote:

> shell\_output = `some process`
> 
> and accidentally see execution fork, is it?

Right, ruby will wait for the process to complete.

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<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [November 20, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543/3 "2006-11-20T14:46:08Z")

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Giles B. wrote:

> shell\_output = `some process`
> 
> and accidentally see execution fork, is it?

That depends on what you put between the back-ticks.

This:

`command > /dev/null &`

will almost certainly fork. There are any number of forking  
contingencies,  
depending on what you try to run, and how.

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<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [November 20, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543/4 "2006-11-20T14:46:10Z")

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Sorry, reading this email reminded me of my project. Say I wanted to do  
a  
bunch of pings using backticks (you may have asked my stupid n00b  
questin  
about ``). If I wanted to do a bunch of pings, which would take some  
small  
amount of time, would it be better(faster) to start new threads before  
doing  
the `ping whatever`, or is there a better/different way?

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<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [November 20, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543/5 "2006-11-20T14:46:13Z")

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Jason M. wrote:

> Sorry, reading this email reminded me of my project. Say I wanted to do a  
> bunch of pings using backticks (you may have asked my stupid n00b questin  
> about ``). If I wanted to do a bunch of pings, which would take some small  
> amount of time, would it be better(faster) to start new threads before  
> doing  
> the `ping whatever`, or is there a better/different way?

Sure, why not use threads:

t0 = Time.now

threads = (1…10).map do |i|  
Thread.new do  
addr = “192.168.0.#{i}”  
[addr, `ping -w3 -nq #{addr}`]  
end  
end

values = threads.map {|thread| thread.value}  
t1 = Time.now  
puts “Finished in #{t1 - t0} seconds”

require ‘yaml’  
y values.select {|addr, out| out !~ / 0 received/}

**END**

Output:

## Finished in 3.011614 seconds

- 
  - 192.168.0.1

  - |  
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.

…

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<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [November 20, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543/6 "2006-11-20T14:46:18Z")

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ok never mind about that last post. it does appear to be pipe commands  
for standard out and standard err and that shouldn’t result in  
backgrounding.

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<div class="post-metadata">

**Author:** ![Giles\_B](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/g/848f3c/32.png) [@Giles\_B](https://www.ruby-forum.com/u/Giles_B)\
**Post date:** [November 20, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/backticks-asynchronous/76543/7 "2006-11-20T14:46:17Z")

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> That depends on what you put between the back-ticks.
> 
> This:
> 
> `command > /dev/null &`
> 
> will almost certainly fork. There are any number of forking contingencies,  
> depending on what you try to run, and how.

well, that’s probably it. the command I’m using is a very long,  
involved command to a complex utility that handles media files, and  
apparently takes an infinite number of command-line arguments, but the  
final args are “2\>&1”. I inherited this code, as I understand it that  
just pipes standard error and standard out to the same place –  
however, now I think that might be what’s going wrong.