/dev/fd/N not synonymous with file descriptor N; it is on Linux

[Houder]

On 2018-12-16 21:28, Corinna Vinschen wrote:
> On Dec 16 17:31, Houder wrote:
>> L.S.,
>> 
>> /dev/fd/N not synonymous with file descriptor N; it is on Linux
> 
> Yes, it is.  Most of the time.  Try this:
> 
> $ echo foo | cat /dev/fd/0
> 
> The problem is that some of the concepts don't work as desired:
> 
>> 64-@@ cat /dev/fd/0 <<\EOF
> 
> If you observe what happens in tcsh in this situation you see that it
> doesn't even execute cat as long as you didn't type EOF.  What you type
> is written to a tmpfile:
> 
> $ ls -l /proc/5980/fd
> total 0
> lrwxrwxrwx 1 corinna vinschen 0 Dec 16 21:15 0 -> /tmp/sh.lVQq04
> lrwxrwxrwx 1 corinna vinschen 0 Dec 16 21:15 15 -> /dev/pty0
> lrwxrwxrwx 1 corinna vinschen 0 Dec 16 21:15 16 -> /dev/pty0
> lrwxrwxrwx 1 corinna vinschen 0 Dec 16 21:15 17 -> /dev/pty0
> lrwxrwxrwx 1 corinna vinschen 0 Dec 16 21:15 18 -> /dev/pty0
> lrwxrwxrwx 1 corinna vinschen 0 Dec 16 21:15 19 -> /dev/pty0
> 
> However, this tmpfile has been unlinked already, so it has been moved 
> to the
> recycle bin:
> 
> $ ls -l /tmp/sh.lVQq04
> ls: /tmp/sh.lVQq04: No such file or directory
> 
> So the path in the fd subdir doesn't reflect the actual file path.
> 
> But after starting cat, cat tries to open /proc/self/fd/0 which
> is in fact the non-existing path /tmp/sh.lVQq04.  Bad luck.

Yes Corinna, I am aware of the above. I described it here:

     https://cygwin.com/ml/cygwin/2018-12/msg00040.html
     ( Re: Bash heredoc on FD 3 )

Sorry for NOT expressing myself more clearly.

The STC is, as I wrote, based on what I observed on Linux.

See attachment.

Regards,
Henri
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