bash3.0的新特性-ps命令

ps命令中的status状态 bash3.0以上支持(kernel 2.6以上)
    D Uninterruptible sleep (usually IO)
    R Running or runnable (on run queue) 运行中
    S Interruptible sleep (waiting for an event to complete) 可打断的后台进程，类似守护进程httpd、ntpd、crond等
    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) 高优先级
    N low-priority (nice to other users) 低优先级
    L has pages locked into memory (for real-time and custom IO)
    s is a session leader 主进程
    l  is multi-threaded (using CLONE_THREAD, like NPTL pthreads do) 表示线程
    + is in the foreground process group 前台运行
 
    譬如：ps -axuf后status column中：Ss表示父进程、R+正在前台运行的进程、SN表示低优先级的进程，S+、Sl表示线程、SL等