Why is stdin always a pipe?

[Heavenly Avenger]

My results match Brian Inglis', not João Eiras'. I run cygwin from a 
putty session (using putty's cygtermd little proxy) if that matters.


On 7/20/2018 11:52 AM, Brian Inglis wrote:
> On 2018-07-20 07:17, João Eiras wrote:
>>>> $ [[ -p /dev/stdin ]] && echo pipe || echo nopipe
>>>> nopipe
>> Interesting, it's always a pipe for me. What about ls ?
>>
>> $ ls -l /dev/stdin
>> prw------- 1 user None 0 Jun  4 15:54 /dev/stdin
> Are you using a terminal that does not provide a console interface?
> That is a pipe; Cygwin terms look like this:
>
> $ ll -go /dev/std*; ll -go /proc/self/fd/[012]; ll -go /dev/pty?
> lrwxrwxrwx 1 15 May 14  2013 /dev/stderr -> /proc/self/fd/2
> lrwxrwxrwx 1 15 May 14  2013 /dev/stdin -> /proc/self/fd/0
> lrwxrwxrwx 1 15 May 14  2013 /dev/stdout -> /proc/self/fd/1
> lrwxrwxrwx 1 0 Jul 20 08:18 /proc/self/fd/0 -> /dev/pty0
> lrwxrwxrwx 1 0 Jul 20 08:18 /proc/self/fd/1 -> /dev/pty0
> lrwxrwxrwx 1 0 Jul 20 08:18 /proc/self/fd/2 -> /dev/pty0
> crw--w---- 1 136, 0 Jul 20 08:18 /dev/pty0
> crw--w---- 1 136, 1 Jul 20 08:18 /dev/pty1
> $ for fd in 0 1 2 3; do test -t $fd; echo fd $fd term $?; done
> fd 0 term 0
> fd 1 term 0
> fd 2 term 0
> fd 3 term 1
> $ for f in /dev/{std*,pty?}; do test -p $f; echo file $f pipe $?; done
> file /dev/stderr pipe 1
> file /dev/stdin pipe 1
> file /dev/stdout pipe 1
> file /dev/pty0 pipe 1
> file /dev/pty1 pipe 1
>
> where ptys are terms and are not pipes.
>


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