/usr/bin/time 文件输入/输出答案

【问题标题】：/usr/bin/time file inputs / outputs/usr/bin/time 文件输入/输出
【发布时间】：2016-10-13 18:48:11
【问题描述】：

我正在努力寻找有关/usr/bin/time -v 的各种输出的确切含义的任何详细信息。即我对文件输入/输出的含义感到困惑。

如果有人对“/usr/bin/time”有一些经验，如果您能帮我解决这个问题，我将不胜感激。

【问题讨论】：

标签： unix time command-line profiling getrusage

【解决方案1】：

你的操作系统是什么，是BSD的linux吗？

time 实用程序（第 1 节）的手册页中有一些字段描述，例如在 Linux 中：http://man7.org/linux/man-pages/man1/time.1.html

但是时间本身使用一些内核接口来获取信息，可能是wait3/wait4http://man7.org/linux/man-pages/man2/wait3.2.html 在time -v 中打印的数据来自struct rusage，在getrusage(2) 手册页中有描述：Linux http://man7.org/linux/man-pages/man2/getrusage.2.html

Linux 有很多字段在使用，但并非所有字段都被使用：

   The resource usages are returned in the structure pointed to by
   usage, which has the following form:

       struct rusage {
           struct timeval ru_utime; /* user CPU time used */
           struct timeval ru_stime; /* system CPU time used */
           long   ru_maxrss;        /* maximum resident set size */
           long   ru_ixrss;         /* integral shared memory size */
           long   ru_idrss;         /* integral unshared data size */
           long   ru_isrss;         /* integral unshared stack size */
           long   ru_minflt;        /* page reclaims (soft page faults) */
           long   ru_majflt;        /* page faults (hard page faults) */
           long   ru_nswap;         /* swaps */
           long   ru_inblock;       /* block input operations */
           long   ru_oublock;       /* block output operations */
           long   ru_msgsnd;        /* IPC messages sent */
           long   ru_msgrcv;        /* IPC messages received */
           long   ru_nsignals;      /* signals received */
           long   ru_nvcsw;         /* voluntary context switches */
           long   ru_nivcsw;        /* involuntary context switches */
       };

http://man7.org/linux/man-pages/man2/getrusage.2.html 还给出了一些描述并标记了未维护的字段：

   ru_utime
   ru_stime
   ru_maxrss (since Linux 2.6.32)
   ru_ixrss (unmaintained)
   ru_idrss (unmaintained)
   ru_isrss (unmaintained)
   ru_minflt
   ru_majflt
   ru_nswap (unmaintained)
   ru_inblock (since Linux 2.6.22)
          The number of times the filesystem had to perform input.
   ru_oublock (since Linux 2.6.22)
          The number of times the filesystem had to perform output.
   ru_msgsnd (unmaintained)
   ru_msgrcv (unmaintained)
   ru_nsignals (unmaintained)
   ru_nvcsw (since Linux 2.6)
   ru_nivcsw (since Linux 2.6)

POSIX 2004 没有要实现的确切列表，因此它是特定于实现的http://pubs.opengroup.org/onlinepubs/009695399/functions/getrusage.html

标头应定义至少包含以下成员的 rusage 结构：
struct timeval ru_utime  User time used. 
struct timeval ru_stime  System time used.

【讨论】：