$ ls -al /dev/std*
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stderr -> fd/2
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdin -> fd/0
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdout -> fd/1
$ ls -n /dev/fd/[012]
crw--w---- 1 501 4 0x10000000 Feb 27 13:38 /dev/fd/0
crw--w---- 1 501 4 0x10000000 Feb 27 13:38 /dev/fd/1
crw--w---- 1 501 4 0x10000000 Feb 27 13:38 /dev/fd/2
$ uname -v
Darwin Kernel Version 24.6.0: Mon Jan 19 22:00:55 PST 2026; root:xnu-11417.140.69.708.3~1/RELEASE_ARM64_T6000
$ sw_vers
ProductName: macOS
ProductVersion: 15.7.4
BuildVersion: 24G517
$ zsh -c 'ls -al /dev/std*'
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stderr -> fd/2
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdin -> fd/0
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdout -> fd/1
$ csh -c 'ls -al /dev/std*'
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stderr -> fd/2
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdin -> fd/0
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdout -> fd/1
$ tcsh -c 'ls -al /dev/std*'
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stderr -> fd/2
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdin -> fd/0
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdout -> fd/1
$ ksh -c 'ls -al /dev/std*'
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stderr -> fd/2
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdin -> fd/0
lr-xr-xr-x 1 root wheel 0 Feb 24 15:08 /dev/stdout -> fd/1
Indeed. At best, they're an "emitter", a "proxy", a "relay", a "transformer", or some combination thereof with "sense" or "marshall" that indicates the transformation of input to output a la "sense proxy emitter" or "marshalling sensor".