通常，ps命令的输出结果是这样的：

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.0  27176  2960 ?        Ss   Sep20   0:02 /sbin/init
root         2  0.0  0.0      0     0 ?        S    Sep20   0:00 [kthreadd]
root         3  0.0  0.0      0     0 ?        S    Sep20  13:05 [ksoftirqd/0]
root         5  0.0  0.0      0     0 ?        S<   Sep20   0:00 [kworker/0:0H]
root         7  0.0  0.0      0     0 ?        S<   Sep20   0:00 [kworker/u:0H]
root         8  0.0  0.0      0     0 ?        S    Sep20   2:16 [migration/0]
root         9  0.0  0.0      0     0 ?        S    Sep20   0:00 [rcu_bh]
root        10  0.0  0.0      0     0 ?        S    Sep20  20:08 [rcu_sched]
root        11  0.0  0.0      0     0 ?        S    Sep20   0:07 [watchdog/0]
root        12  0.0  0.0      0     0 ?        S    Sep20   0:05 [watchdog/1]
root        13  0.0  0.0      0     0 ?        S    Sep20   2:21 [ksoftirqd/1]
root        14  0.0  0.0      0     0 ?        S    Sep20   1:00 [migration/1]

其中STAT列的各个标识的含义如下：
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.