c - getrusage在ru_utime.tv_usec和ru_utime.tv_sec中返回零

对于以下代码，getrusage在ru_utime.tv_usec和ru_utime.tv_sec中返回零。

码：

#include "stdlib.h"
#include "stdio.h"
#include "sys/time.h"
#include "sys/resource.h"

int getr_return, who = RUSAGE_SELF;
struct rusage usage;

main()
{
    getr_return = getrusage(who, &usage);
    printf(" getr_return = %d\n", getr_return);

    printf(" time taken in seconds = %.61f\n", usage.ru_utime.tv_sec);
    printf(" time taken in seconds = %.61f\n", usage.ru_utime.tv_usec);


        Some_Mips_consuming_code().


        getr_return = getrusage(who, &usage);
        printf(" getr_return = %d\n", getr_return);

        printf(" time taken in seconds = %.61f\n", usage.ru_utime.tv_sec);
        printf(" time taken in seconds = %.61f\n", usage.ru_utime.tv_usec);

    exit;
 }

输出：

getr_return = 0
time taken in seconds =  0.0000000000000000000000000000000000000000000000000000000000000
time taken in seconds =  0.0000000000000000000000000000000000000000000000000000000000000
getr_return = 0
time taken in seconds =  0.0000000000000000000000000000000000000000000000000000000000000
time taken in seconds =  0.0000000000000000000000000000000000000000000000000000000000000

Linux version 2.6.18-308上的已编译代码

在ARM板上运行可执行文件，它是Linux version 3.8.1-2.0

最佳答案

在逻辑的两个瞬间之间计算用户使用时间，以找出消耗的时间，该时间应具有timeval的开始和结束使用时间。例如下面的示例

 struct timeval start, end;
 getrusage(RUSAGE_SELF, &usage);
 start = usage.ru_utime;
 /* Code to check the usage consumed */
 getrusage(RUSAGE_SELF, &usage);
 end = usage.ru_utime;

ru_utime和ru_stime是timeval类型的结构。如果查看其declaration，则两个成员tv_sec和tv_usec的类型均为long。因此，在打印到%ld时，请更改格式说明符。请注意，成功时getrusage()返回0。