# Help on I/O pipe

**URL:** <https://www.ruby-forum.com/t/help-on-i-o-pipe/51567>\
**Category:** Ruby\
**Created:** [January 3, 2006, 1:35pm UTC](https://www.ruby-forum.com/t/help-on-i-o-pipe/51567 "2006-01-03T13:35:50Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![cookoo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cookoo](https://www.ruby-forum.com/u/cookoo)\
**Post date:** [January 3, 2006, 1:35pm UTC](https://www.ruby-forum.com/t/help-on-i-o-pipe/51567/1 "2006-01-03T13:35:50Z")

</div>

One process of my analysis program uses an external non-linear  
optimizer.  
That optimizer needs a model file as the argument. The current approach  
I  
employ to accomplish this is to create a model file on disk everytime  
running the optimizer. The code is simply like

@model = File.open(“model.mod”, “w”)  
…  
@model.close  
result = `optimizer.exe model.mod`

The problem is that I have to repeat running optimizer on different  
models  
many many times during the analysis. I wonder if such heavy writing on a  
single file will do any harm to my hard disk. My concern of improving it  
is  
to use I/O pipe to feed the optimizer without the needs to create real  
model  
files. Can anyone give me some tips or examples on using the shell pipe?  
The  
rdoc isn’t so clear.

Thanks

---

<div class="post-metadata">

**Author:** ![cookoo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cookoo](https://www.ruby-forum.com/u/cookoo)\
**Post date:** [January 3, 2006, 3:20pm UTC](https://www.ruby-forum.com/t/help-on-i-o-pipe/51567/2 "2006-01-03T15:20:46Z")

</div>

Sky Y. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) writes:

> The problem is that I have to repeat running optimizer on different models  
> many many times during the analysis.

> I wonder if such heavy writing on a single file will do any harm to  
> my hard disk.

Unlikely. HD does not have a limitation on number of writes like CD-RW  
and flash drives (USB key chains, SD, memory stick, etc.)

> My concern of improving it is to use I/O pipe to feed the optimizer  
> without the needs to create real model files.

Before you can use pipe, you have to know if optimizer.exe read  
model.mod sequentially or not.

If it reads model.mod sequentially, then you can use pipe. Otherwise,  
you’d need to write it to a file (basically do what you are doing  
above).

There are two kind of pipe: anonymous pipe and named pipe.

Anonymous pipe is setup automatically by your environment (your shell  
in unix or cmd.exe in win32) when you do:

foo | bar

For this to work, your model generator just need to write to its  
standard output ($stdout in ruby) and your optimizer.exe reads from  
its standard input. This may require changes to optimizer.exe as I  
don’t think it is common for a win32 program to read from stdin (some  
kind of aversion to CLI?)

Named pipe involves creating a special file in the filesystem. Your  
model generator opens this file in write mode and start writing. At  
about the same time, you need to invoke optimizer.exe to read from  
this file: optimizer.exe specialfile.mod. The data transfer will not  
go through disk I/O. However, I’m not sure if win32 supports named  
pipe.

> Can anyone give me some tips or examples on using the shell pipe?

As I explained above, shell pipe needs to be setup by your  
environment. You can, of course, set up your own pipe programatically,  
but as I’m not a win32 programmer, I don’t know how or even if that is  
possible since the process model of Unix and Win32 are different.

YS.

---

<div class="post-metadata">

**Author:** ![cookoo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cookoo](https://www.ruby-forum.com/u/cookoo)\
**Post date:** [January 3, 2006, 3:33pm UTC](https://www.ruby-forum.com/t/help-on-i-o-pipe/51567/3 "2006-01-03T15:33:29Z")

</div>

On Tue, 3 Jan 2006, Sky Y. wrote:

> The problem is that I have to repeat running optimizer on different models  
> many many times during the analysis. I wonder if such heavy writing on a  
> single file will do any harm to my hard disk. My concern of improving it is  
> to use I/O pipe to feed the optimizer without the needs to create real model  
> files. Can anyone give me some tips or examples on using the shell pipe? The  
> rdoc isn’t so clear.
> 
> Thanks

assuming that your analysis code can read it’s input sequentially you  
might  
want to try session:

require ‘session’

sh = Session::new

model\_input = …

stdout, stderr = sh.execute ‘optimizer.exe’, ‘stdin’ =\> model\_input

p sh.exitstatus

regards.

-a

---

<div class="post-metadata">

**Author:** ![cookoo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cookoo](https://www.ruby-forum.com/u/cookoo)\
**Post date:** [January 4, 2006, 12:04am UTC](https://www.ruby-forum.com/t/help-on-i-o-pipe/51567/4 "2006-01-04T00:04:19Z")

</div>

On Wed, 4 Jan 2006, Sky Y. wrote:

> As for the session gem, I installed, but require ‘session’ simply returns a  
> false under Win32.
> 
> Thanks anyway.

session is not going to work under win32. you’ll need to do something  
like

io = IO.popen(“optimizer.exe”, “r+”)

io.puts “…” # stdin\<model.mod

io.close\_write

stdout = io.read

io.close

to avoid hanging on a gets with line buffered output.

regards.

-a

---

<div class="post-metadata">

**Author:** ![cookoo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cookoo](https://www.ruby-forum.com/u/cookoo)\
**Post date:** [January 3, 2006, 11:58pm UTC](https://www.ruby-forum.com/t/help-on-i-o-pipe/51567/5 "2006-01-03T23:58:10Z")

</div>

Thank Yohanes for the detailed explanation. I’ve just tried using

io = IO.popen(“optimizer.exe”, “r+”)  
io.puts “…” #stdin\<model.mod  
io.gets #stdout  
…  
io.close

It’s weird that first two io.gets worked OK to retrieve the first two  
lines  
of the result, but then io.gets halted on the third io.gets. No clue.

As for the session gem, I installed, but require ‘session’ simply  
returns a  
false under Win32.

Thanks anyway.

---

<div class="post-metadata">

**Author:** ![cookoo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/c89c15/32.png) [@cookoo](https://www.ruby-forum.com/u/cookoo)\
**Post date:** [January 4, 2006, 3:00am UTC](https://www.ruby-forum.com/t/help-on-i-o-pipe/51567/6 "2006-01-04T03:00:59Z")

</div>

It works very smoothly now. Thanks a lot for the timely help.  
Everyday I love ruby a bit more :^)