Bash and zsh also allow, and modern Borne-compatible shells (sh) might too: echo >&2 error_message On Linux, /dev/std* requires the kernel to do file name

Bash and zsh also allow, and modern Borne-compatible shells (sh) might too: echo >&2 error_message On Linux, /dev/std* requires the kernel to do file name resolution in the virtual file system because it could point to something nonstandard that isn't a symlink to something like /proc/self/fd/XX and then the kernel has to check that that should hopefully point to a special character device.