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Date: Sun, 03 Jan 2016 23:47:06 +0100
From: Houder <houder AT xs4all DOT nl>
To: cygwin AT cygwin DOT com
Subject: Re: Pipes Again. (was: cmp (or echo) bug?) -- more correction
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On 2016-01-02 12:58, Houder wrote:

> Cygwin shows:
> @@ ./t_stat <(echo foo) <(echo bar)
> ... arg = /dev/fd/63
> File type:                FIFO or pipe
> Device containing i-node: (c6)   major=0   minor=198
> I-node number:            0 - decimal: 0
> ... arg = /dev/fd/62
> File type:                FIFO or pipe
> Device containing i-node: (c6)   major=0   minor=198
> I-node number:            0 - decimal: 0
> fd[0] = 3, fd[1] = 3
> 
> And sometimes, especially in case close(fd[f]) is NOT present ...
> 
> @@ ./t_stat <(echo foo) <(echo bar)
> ... arg = /dev/fd/63
> File type:                FIFO or pipe
> Device containing i-node: (c6)   major=0   minor=198
> I-node number:            0 - decimal: 0
> ... arg = /dev/fd/62
> File type:                FIFO or pipe
> Device containing i-node: (c6)   major=0   minor=198
> I-node number:            5c443bd7b7e540 - decimal: 25970721670292800
> fd[0] = 3, fd[1] = 4
> 
>  - Cygwin shows 198 for st_dev in case fstat() is used
>  - Cygwin shows 199 for st_dev in case stat() is used
>  - Cygwin shows 197 for st_dev in case fstat() is used and in case the 
> command
>    reads as follows:
> @@ ./t_stat >(cat > a) >(cat > b) # yes, the opposite case - had to try
> 
>  - Cygwin nearly always shows ZERO for both st_ino-s (same call); 
> however, if
>    one of the st_ino-s is NOT zero, Cygwin always shows the same value:
> I-node number:            5c443bd7b7e540 - decimal: 25970721670292800

Should be read:

  - Cygwin nearly always shows ZERO ... etc., etc. in case of fstat() 
!!!!!
  - Cygwin always shows different values for both st_ino-s (same call) in 
case of
    stat(); values that are different from the ones in subsequent calls

Sorry,
Henri

> Bottom-line:
> 
>  - instrumenting cmp with the same "diagnostics", yields the same 
> result
>  - cmp fails on Cygwin, because Cygwin returns both st_ino-s as equal 
> (zero).
> 
> My reason for posting this, is to help others in case they stumble over 
> this
> weird behaviour of Cygwin.

=====

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