command help

[Tom Allison]

Found a buddy who used something like:

hostname = open("|hostname").gets

And...

I see that it works, but I don't find any of the documentation that makes sense.

So -- it seems to be IO class, but how? There's no IO declaration there.
Also, I can't find anything that says you can open a command with a preceding
pipe and get the output of the executed command.

I'm familiar with perls open: open(FH, "hostname |") with a suffixed pipe --
which is consistent with unix pipe usage.

But can someone explain to me what's going on here so my brain doesn't implode?

 

[Jan Svitok]

Found a buddy who used something like:

hostname = open("|hostname").gets

And...

I see that it works, but I don't find any of the documentation that makes sense.

So -- it seems to be IO class, but how? There's no IO declaration there.
Also, I can't find anything that says you can open a command with a preceding
pipe and get the output of the executed command.

I'm familiar with perls open: open(FH, "hostname |") with a suffixed pipe --
which is consistent with unix pipe usage.

But can someone explain to me what's going on here so my brain doesn't implode?

http://ruby-doc.org/core/classes/Kernel.html#M001989

 

[Bil Kleb]

But can someone explain to me what's going on here so my brain doesn't
implode?

Throw back to the old ftp pipe days? E.g., see,

http://www.ii.com/internet/ftp/archie_ftp_uncompression/

Later,

 

[Tom Allison]

http://ruby-doc.org/core/classes/Kernel.html#M001989

OK, I missed the "Kernel#open" in the list of where I can use open. NOTE: the
list from 'ri' could be better formatted.

What's with the pipe being at the wrong end?
What's the thinking behind that?

 

[ara.t.howard]

What's with the pipe being at the wrong end?
What's the thinking behind that?

" open a pipe to the command X "

just guessing...

-a

 

[Pit Capitain]

What's with the pipe being at the wrong end?
What's the thinking behind that?

You can find a short description in ri or the Pickaxe:

C:\tmp>ri IO
-------------------------------------------------------------- Class: IO
Class +IO+ is the basis for all input and output in Ruby. An I/O
stream may be _duplexed_ (that is, bidirectional), and so may use
more than one native operating system stream.

Many of the examples in this section use class +File+, the only
standard subclass of +IO+. The two classes are closely associated.

As used in this section, _portname_ may take any of the following
forms.

* A plain string represents a filename suitable for the
underlying operating system.
* A string starting with ``+|+'' indicates a subprocess. The
remainder of the string following the ``+|+'' is invoked as a
process with appropriate input/output channels connected to it.
* A string equal to ``+|-+'' will create another Ruby instance as
a subprocess.

Regards,
Pit