On Wed, Sep 19, 2012 at 9:54 PM, David Glasser <glas...@meteor.com> wrote:
> See https://gist.github.com/3751746 for details.

> Basically, in Node 0.6, if you start a child_process with
> child_process.spawn, the pipe2 system call was used to create the
> pipes between parent and child.

> This was changed (I believe) in this commit by indutny:
> https://github.com/joyent/libuv/commit/c0081f0e6675131721dbb5138fd398...

> Now the socketpair call is used to create those fds.

> I'm not sure why that choice was made, but it has at least one bad
> effect: it breaks the ability to use "/dev/stdin" or "/proc/self/fd/0"
> on the child, at least on Linux.

> The gist shows a Node program that basically just spawns "cat
> /proc/self/fd/0", closes the pipe to the cat, and shows what the cat
> outputs. In 0.6.17 cat happily cats the empty stdin and exits 1. In
> 0.8.8 cat fails to open the /proc/self/fd/0.

> The C program in the gist shows that the difference really is just
> socketpair vs pipe2. If you run the version with pipe2 the open call
> succeeds. Comment out pipe2 and uncomment socketpair, and the open
> call fails.

> Was this behavior change intentional?

> What benefits are created by switching from pipe2 to socketpair?

});

On Wednesday, September 19, 2012 6:20:23 PM UTC-4, Ben Noordhuis wrote:

> On Wed, Sep 19, 2012 at 9:54 PM, David Glasser <gla...@meteor.com<javascript:>>
> wrote:
> > See https://gist.github.com/3751746 for details.

> > Basically, in Node 0.6, if you start a child_process with
> > child_process.spawn, the pipe2 system call was used to create the
> > pipes between parent and child.

> > This was changed (I believe) in this commit by indutny:

> https://github.com/joyent/libuv/commit/c0081f0e6675131721dbb5138fd398...

> > Now the socketpair call is used to create those fds.

> > I'm not sure why that choice was made, but it has at least one bad
> > effect: it breaks the ability to use "/dev/stdin" or "/proc/self/fd/0"
> > on the child, at least on Linux.

> > The gist shows a Node program that basically just spawns "cat
> > /proc/self/fd/0", closes the pipe to the cat, and shows what the cat
> > outputs. In 0.6.17 cat happily cats the empty stdin and exits 1. In
> > 0.8.8 cat fails to open the /proc/self/fd/0.

> > The C program in the gist shows that the difference really is just
> > socketpair vs pipe2. If you run the version with pipe2 the open call
> > succeeds. Comment out pipe2 and uncomment socketpair, and the open
> > call fails.

> > Was this behavior change intentional?

> Yes.

> > What benefits are created by switching from pipe2 to socketpair?

> The ability to send file descriptors to the child process (which was
> something you could do in v0.4 but not v0.6).

> It's been brought up on the issue tracker a few times. A
> straightforward workaround is to insert a pipe. E.g.:

>   spawn('foo')

> Becomes:

>   spawn('/bin/sh', ['-c', 'cat | foo'])

On Thu, Sep 20, 2012 at 4:07 PM, dhruvbird <dhruvb...@gmail.com> wrote:
> Hello,

> So, I'm still trying to understand the implications of this change. Suppose
> I spawn "cat" and write to the stdin of the spawned process, then will the
> "cat" process not be able to read it?

> var cat = spawn('cat');
> cat.stdin.write('Foo Bar');
> cat.stdout.on('data', function(d) { console.log("Child Says:", String(d);
> });

> Will this do what I expect it to?

On Thu, Sep 20, 2012 at 9:18 AM, Ben Noordhuis <i...@bnoordhuis.nl> wrote:
> On Thu, Sep 20, 2012 at 4:07 PM, dhruvbird <dhruvb...@gmail.com> wrote:
>> Hello,

>> So, I'm still trying to understand the implications of this change. Suppose
>> I spawn "cat" and write to the stdin of the spawned process, then will the
>> "cat" process not be able to read it?

>> var cat = spawn('cat');
>> cat.stdin.write('Foo Bar');
>> cat.stdout.on('data', function(d) { console.log("Child Says:", String(d);
>> });

>> Will this do what I expect it to?

> Yes. It's only when the child process explicitly opens /dev/stdin (or
> /dev/stdout) that it doesn't work.

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On Wed, Sep 26, 2012 at 12:43 AM, Shawn Parrish <sparr...@nodeping.com> wrote:
> Ben,

> I noticed this line in the announcement for 0.8.10

> * unix: put child process stdio fds in blocking mode (Ben Noordhuis)

> Does that by any chance address this issue?  I continue to struggle with it.