linux cmd: ps

每天一个linux命令（41）：ps命令 http://www.cnblogs.com/peida/archive/2012/12/19/2824418.html

Linux中的ps命令是Process Status的缩写。ps命令用来列出系统中当前运行的那些进程。ps命令列出的是当前那些进程的快照，就是执行ps命令的那个时刻的那些进程，如果想要动态的显示进程信息，就可以使用top命令。

ps 为我们提供了进程的一次性的查看，它所提供的查看结果并不动态连续的；如果想对进程时间监控，应该用 top 工具。

kill 命令用于杀死进程。

linux上进程有5种状态: 

1. 运行(正在运行或在运行队列中等待) 

2. 中断(休眠中, 受阻, 在等待某个条件的形成或接受到信号) 

3. 不可中断(收到信号不唤醒和不可运行, 进程必须等待直到有中断发生) 

4. 僵死(进程已终止, 但进程描述符存在, 直到父进程调用wait4()系统调用后释放) 

5. 停止(进程收到SIGSTOP, SIGSTP, SIGTIN, SIGTOU信号后停止运行运行) 

ps工具标识进程的5种状态码: 

D 不可中断 uninterruptible sleep (usually IO) 

R 运行 runnable (on run queue) 

S 中断 sleeping 

T 停止 traced or stopped 

Z 僵死 a defunct (”zombie”) process

ps

ps -aux

...

• ps 后的 stat列,有如下:Ss+ ,SN,S<,Ssl不知道是什么意思?

PROCESS STATE CODES
Here are the different values that the s, stat and state output specifiers
(header "STAT" or "S") will display to describe the state of a process.
D    Uninterruptible sleep (usually IO)
R    Running or runnable (on run queue)
S    Interruptible sleep (waiting for an event to complete)
T    Stopped, either by a job control signal or because it is being traced.
W    paging (not valid since the 2.6.xx kernel)
X    dead (should never be seen)
Z    Defunct ("zombie") process, terminated but not reaped by its parent.

For BSD formats and when the stat keyword is used, additional characters may
be displayed:
<    high-priority (not nice to other users)
N    low-priority (nice to other users)
L    has pages locked into memory (for real-time and custom IO)
s    is a session leader
l    is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
+    is in the foreground process group