with seq 1 10 | vim - | cat > x, I get "Vim: Warning: Output is not to a terminal" and the pipeline appears to hang, but actually the output is going to "x". In

with seq 1 10 | vim - | cat > x, I get "Vim: Warning: Output is not to a terminal" and the pipeline appears to hang, but actually the output is going to "x". In other words, your command deletes some unknown files depending on your terminal setup.