在Linux中执行ps aux命令时，STAT列表示的是进程的状态。最近研究了一下进程状态码，这里做一个简单的总结。 下面是是ps的manual中给出的信息，本文将分别介绍每个状态

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 by job control signal
               t    stopped by debugger during the tracing
               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

R running or runnable (on run queue)

进程正在CPU上运行，或者在排队等待CPU

S interruptible sleep (waiting for an event to complete)

进程处于可打断睡眠状态，在等待某些事件来打断睡眠状态（如硬件中断、进程等待的资源可获得、获得接收到某些信号等）

D uninterruptible sleep (usually IO)

进程处于睡眠不可打断的睡眠状态，发送信号并不能改变睡眠状态，通常是在等待某些IO操作完成（如等待设备驱动完成设备扫描）

T stopped by job control signal

进程执行终止，进程在接收到SIGSTOP, SIGTSTP, SIGTTIN, SIGTTOU中任意一个时会进入该状态，在终端中使用Ctrl^Z会使得正在运行的进程进入后台（发送的信号是SIGTSTP）

t stopped by debugger during the tracing

进程因为调试暂停了，比如调试器调用ptrace()进程时，进程暂停时就会进入这种状态

X dead (should never be seen)

进程已经死亡

Z defunct (“zombie”) process, terminated but not reaped by its parent

僵尸进程，进程已经结束运行，但是该进程的父进程还没有为它调用wait4()或者waitpid()。在wait调用之前内核不会丢弃已经结束运行的进程的数据，因为父进程可能需要这些数据。(和这个相关的一个概念是孤儿进 程，指的是父进程先结束，子进程还在运行，子进程就变成了孤儿进程，由pid为1的init进程收养，其ppid会变成1）

< high-priority (not nice to other users)

高优先级进程（静态优先级相关的概念）

N low-priority (nice to other users)

低优先级进程（静态优先级相关的概念）

L has pages locked into memory (for real-time and custom IO)

进程要求内核讲自己的部分内存维持在内存中，不要cache out到磁盘中

s is a session leader

该进程是所在会话的leader进程

l is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)

该进程包含多个线程

+ is in the foreground process group

运行在前台的进程，就是你直接在终端中执行命令并在当前终端等待其完成的进程