osboxes@osboxes:~/proto/bin$ ll | grep stack0
-rwsr-xr-x 1 root root 22412 Jan 22 07:16 stack0*
bash: ./stack0: No such file or directory
The program is marked as executable, but trying to execute it says there is no such file or directory. I didn't even notice it, because radare2 and gdb were able to execute it.