6、UNIX 编程基础与文件操作详解

UNIX 编程基础与文件操作详解

1. 示例代码相关

示例代码中有一段用于测量 getpid() 调用时间的程序：

snprintf(msg, sizeof(msg), "%d getpids", REPS);
ec_neg1( c1 = clock() )
gettimeofday(&tv1, NULL);
timestart();
for (i = 0; i < REPS; i++)
    (void)getpid();
(void)sleep(2);
timestop(msg);
gettimeofday(&tv2, NULL);
ec_neg1( c2 = clock() )
printf("clock(): %.2f\n", (double)(c2 - c1) / CLOCKS_PER_SEC);
printf("gettimeofday(): %.2f\n", TV_SUBTRACT(tv2, tv1));
exit(EXIT_SUCCESS);
EC_CLEANUP_BGN
    exit(EXIT_FAILURE);
EC_CLEANUP_END

在 Linux 系统上运行该程序的输出如下：

1000000 getpids:
        "Total (user/sys/real)", 0.72, 0.44, 3.19
        "Child (user/sys)", 0.00, 0.00
clock(): 1.16
gettimeofday(