Problem with <> redirection to named pipe

Problem with <> redirection to named pipe

[Nikolay Shirokovskiy]

Hello.

When I try:

> mkfifo fifo
> exec 5<>fifo

I get "Device or resource busy" error message. On linux distro these
lines work well.

I made some browising through archives and encountered notices that
FIFOs implementation
in Cygwin is incomplete. Is this the cause or I miss something?

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Re: Problem with <> redirection to named pipe

[marco atzeri]

On 7/19/2012 8:53 AM, Nikolay Shirokovskiy wrote:
> Hello.
>
> When I try:
>
>> mkfifo fifo
>> exec 5<>fifo
>
> I get "Device or resource busy" error message. On linux distro these
> lines work well.

no error massages on latest snapshot (http://cygwin.com/snapshots/)

$ uname -a
CYGWIN_NT-6.1-WOW64 ........... 1.7.16s(0.261/5/3) 20120715 16:28:30 
i686 Cygwin

>
> I made some browising through archives and encountered notices that
> FIFOs implementation
> in Cygwin is incomplete. Is this the cause or I miss something?
>

What is your cygwin version ?

Regards
Marco



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Re: Problem with <> redirection to named pipe

[Eric Blake]

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On 07/19/2012 12:53 AM, Nikolay Shirokovskiy wrote:
> Hello.
> 
> When I try:
> 
>> mkfifo fifo
>> exec 5<>fifo

POSIX says this is non-portable.  You cannot expect it to work everywhere.

> 
> I get "Device or resource busy" error message. On linux distro these
> lines work well.

As an extension to POSIX, but not as a standard.

> 
> I made some browising through archives and encountered notices that
> FIFOs implementation
> in Cygwin is incomplete. Is this the cause or I miss something?

I don't know if cgf's recent work on fifos has achieved the same
extension as Linux of being able to open a fifo for read-write; but I
know that Autoconf specifically avoids using <> on fifos, and instead
uses a background subshell where the two forks of the shell coordinate
which shell opens for read and the other opens for write, precisely
because of cygwin.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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