 $ echo foo | tee /proc/self/fd/{0..0} 0>&0 tee: /proc/self/fd/0: No such file or directory tee: /proc/self/fd/0: No such file or directory tee: /proc/self/fd/0: No such file or directory foo foo $ echo foo | tee /proc/self/fd/{0..0} 0>&0 tee: /proc/self/fd/0: No such file or directory tee: /proc/self/fd/0: No such file or directory foo foo 