使用Bash计算程序的平均执行时间

Question

为了获得任何可执行文件的执行时间,比方说a.out,我可以简单地写一下time ./a.out.这将输出实时,用户时间和系统时间.

是否有可能编写一个运行程序多次的bash脚本并计算并输出平均实际执行时间？

Answer 1

您可以编写一个循环并收集time命令的输出并将其传递awk给计算平均值:

avg_time() {
    #
    # usage: avg_time n command ...
    #
    n=$1; shift
    (($# > 0)) || return                   # bail if no command given
    for ((i = 0; i < n; i++)); do
        { time -p "$@" &>/dev/null; } 2>&1 # ignore the output of the command
                                           # but collect time's output in stdout
    done | awk '
        /real/ { real = real + $2; nr++ }
        /user/ { user = user + $2; nu++ }
        /sys/  { sys  = sys  + $2; ns++}
        END    {
                 if (nr>0) printf("real %f\n", real/nr);
                 if (nu>0) printf("user %f\n", user/nu);
                 if (ns>0) printf("sys %f\n",  sys/ns)
               }'
}

例:

avg_time 5 sleep 1

会给你的

real 1.000000
user 0.000000
sys 0.000000

这可以很容易地增强到:

• 在执行之间睡一段时间
• 在执行之间睡眠一段随机时间(在一定范围内)

time -p来自的含义man time:

   -p
      When in the POSIX locale, use the precise traditional format

      "real %f\nuser %f\nsys %f\n"

      (with  numbers  in seconds) where the number of decimals in the
      output for %f is unspecified but is sufficient to express the
      clock tick accuracy, and at least one.

您可能还想查看此命令行基准测试工具:

sharkdp /超精细