PS命令
常用ps命令：
ps aux // 显示有效用户ID或名字
ps awx // 显示完全程序参数
ps ajx //Jobs格式，显示PPID，PID，PGID，SID，UID，COMMAND等
字段含义：
PPID：父进程ID
PGID：Process Group ID 进程组ID
TGID：Thread Group ID线程组ID
SID：Session ID 回话ID
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.
