$ ls -l /proc/self/fd/ <<< "TEST"
total 0
lr-x------ 1 user1 user1 64 Aug 20 13:43 0 -> /tmp/sh-thd.761Lj9 (deleted)
lrwx------ 1 user1 user1 64 Aug 20 13:43 1 -> /dev/pts/4
lrwx------ 1 user1 user1 64 Aug 20 13:43 2 -> /dev/pts/4
lr-x------ 1 user1 user1 64 Aug 20 13:43 3 -> /proc/10068/fd