Feature #2631: Allow IO#reopen to take a block

• Status: Assigned
• Assignee: Glass_saga (Masaki Matsushita)
• Target version: -

[djberg96 (Daniel Berger)]

=begin
Please allow IO#reopen to accept a block. This would allow users to temporarily redirect output without having to manually reset the file descriptor. For example:

require 'mkmf'

stdout redirected within block only

$stdout.reopen('/dev/null') do
if have_header('foo.h')
# Do stuff
end
end

stdout now back to its former setting

I believe this is both convenient and intuitive when one considers the IO.open also takes a block.

Regards,

Dan
=end

[hongli (Hongli Lai)]

=begin
I don't think this can be implemented easily. This can be implemented if the IO object in question is a File for which you know the filename. For sockets, pipes and other stuff it becomes tricker: one can emulate it backing up the underlying file descriptor by dup()ing it, but in my opinion that goes against my expectation of what #reopen should do: to replace the file descriptor with something else.
=end

[matz (Yukihiro Matsumoto)]

Hi,

In message "Re: [ruby-core:27702] [Feature #2631] Allow IO#reopen to take a block"
on Sat, 23 Jan 2010 01:30:53 +0900, Hongli Lai [e-mail] writes:

I don't think this can be implemented easily. This can be implemented if the IO object in question is a File for which you know the filename. For sockets, pipes and other stuff it becomes tricker: one can emulate it backing up the underlying file descriptor by dup()ing it, but in my opinion that goes against my expectation of what #reopen should do: to replace the file descriptor with something else.

Agreed. Besides that behavior would not be thread safe.

						matz.

[shyouhei (Shyouhei Urabe)]

+1, The idea of temporary intercepting any output to another IO is worth considering. Though I doubt to name that feature a "reopen".

So my suggestion is: create a new method, that takes a block, to intercept an IO.

[djberg96 (Daniel Berger)]

On Fri, Jan 22, 2010 at 10:56 PM, Shyouhei Urabe [e-mail] wrote:

Issue #2631 has been updated by Shyouhei Urabe.

+1, The idea of temporary intercepting any output to another IO is worth considering.  Though I doubt to name that feature a "reopen".

How about IO#redirect.

[znz (Kazuhiro NISHIYAMA)]

• Category set to core
• Target version set to 2.0.0

[nahi (Hiroshi Nakamura)]

• Description updated (diff)
• Assignee set to shyouhei (Shyouhei Urabe)

Method name?

[akr (Akira Tanaka)]

I don't feel changing IO#reopen is great way to solve this issue.

How about spawn()?

Since Ruby 1.9, spawn provides a primitive for redirection.
It is thread safe.

Apart from that, I think $stdin, $stdout, $stderr can be thread-local
variables, though.

[shyouhei (Shyouhei Urabe)]

• Status changed from Open to Assigned

[shyouhei (Shyouhei Urabe)]

• Target version changed from 2.0.0 to 2.6

I was poked by _ko1. But we lack a implementation proposal.

So I move its target to next minor. It might happen to be implemented some time later but not today.

Any opinions?

• Status changed from Assigned to Closed

Applied in changeset trunk|r59142.

---

Allow IO#reopen to take a block

• io.c (rb_io_reopen): take a block and ensure the IO closed
  [Feature #2631]

• test/ruby/test_io.rb: add a test

• NEWS: add an entry for this change

[naruse (Yui NARUSE)]

• Status changed from Closed to Open

匿名ユーザー wrote:

Applied in changeset trunk|r59142.

---

Allow IO#reopen to take a block

• io.c (rb_io_reopen): take a block and ensure the IO closed
  [Feature #2631]

• test/ruby/test_io.rb: add a test

• NEWS: add an entry for this change

This patch looks doesn't recover the original $stdout.

Morever though this was approved before, this is strange because block changes global state.
If this is introduced in 7 years ago, it may be acceptable.
But in this 201x year Ruby really should support multithread unsafe code?
People who want to write unsafe code should explicitly write code like following.

require 'mkmf'

# stdout redirected within block only
orig_stdout = $stdout
open(IO:NULL, 'w') do |f|
  $stdout = f
  if have_header('foo.h')
    # Do stuff
  end
ensure
  $stdout = orig_stdout
end

[naruse (Yui NARUSE)]

• Target version changed from 2.6 to 2.5

[Glass_saga (Masaki Matsushita)]

• Status changed from Open to Closed
• Assignee changed from shyouhei (Shyouhei Urabe) to Glass_saga (Masaki Matsushita)

[Glass_saga (Masaki Matsushita)]

• Status changed from Closed to Assigned

[Glass_saga (Masaki Matsushita)]

It was thoughtless. Let me revert it.

[naruse (Yui NARUSE)]

• Target version deleted (2.5)

[Bookgoogleflights (google flights)]

The idea of temporary intercepting any output to another IO is worth considering. Though I doubt to name that feature a "reopen".est/ruby/test_io.rb: add a test NEWS: add an entry for this change, he new Google Flights offers all of the speed and usability of the old Google Flights, but with some great new features added on top book flights using "bookgoogleflights.wordpress.com":https://bookgoogleflights.wordpress.com/