有关详细信息，请参阅以下联机帮助页：

杀死(1)

$ man 1 kill
...
If sig is 0,then no signal is sent,but error checking is still performed.
...

杀死(2)

$ man 2 kill
...
If sig is 0,but error checking is still performed; this 
can be used to check for the existence of a process ID or process group ID.
...