infant:~$ ps a | grep 13179 13179 pts/20 R 0:18 /bin/bash ./Z 13181 pts/20 S+ 0:00 grep --color=auto 13179 infant:~$ kill 13179 infant:~$ kill 13179 bash: kill: (13179) - No such process + Terminated ./Z
"Zed's dead, baby. Zed's dead." from Pulp Fiction. My guess is because you're attempting to kill a process that's been terminated already. The system replies with a message that Z's been terminated and process is not found on the second attempt to kill the process.