如何查看按進程在當前時間執行的系統調用？

Question

Linux實用程序「strace」顯示strace運行後啓動的系統調用列表。我如何看到按流程在當前運行的系統調用？ strace開始之前。

Answer 1

proc提供什麼內核目前正在做 「爲」 過程的一些信息
/proc/${pid}/syscall /proc/${pid}/stack

的更多信息：

• http://man7.org/linux/man-pages/man5/proc.5.html
• http://blog.tanelpoder.com/2013/02/21/peeking-into-linux-kernel-land-using-proc-filesystem-for-quickndirty-troubleshooting/

Answer 2

你發現使用ps：

ps -p PID_OF_PROC -ocmd,stat,wchan 

wchan是這裏的關鍵。從man ps：

WCHAN WCHAN內核函數中的過程中處於睡眠狀態，一個名「 - 」如果正在運行的進程，或 「*」，如果進程是多線程和ps不顯示線程。

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PROCESS狀態代碼 這裏有不同的值，該S，STAT和狀態輸出說明符（標頭「STAT」或「S」）將顯示描述 的狀態過程：

  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