p7-2.c

UNIX程序设计教程

#include <stdio.h>
#include <sys/types.h>
#include <sys/times.h>
#include <math.h>
#include <sys/wait.h>
#include <unistd.h>
#define KIDNUM 3
void work(int);
void tell_times(struct tms *, clock_t, clock_t);
int main (void)
{
    clock_t start, stop;
    struct tms buffer;
    int i;
    pid_t pid;
    start = times(&buffer);
    printf("       start time: %u (ticks)\n",start);  
    printf(" utime: %d (ticks),  stime: %d (ticks)\n"
           "cutime: %d (ticks), cstime: %d (ticks)\n",
           buffer.tms_utime, buffer.tms_stime, 
           buffer.tms_cutime, buffer.tms_cstime);
    for (i = 1; i <= KIDNUM; i++)  
        if( !(pid = fork()) ){      /* 子进程代码 */
           work(i);
           exit(0);
        }
    /* 父进程代码 */
    work(KIDNUM+1);
    for(i = 0; i < KIDNUM; i++){  /* 等待子进程并计算子进程所花的时间 */
        pid = wait(NULL);
        printf("Child %d, now terminate.\n", pid);
        stop = times(&buffer);
        tell_times(&buffer, start, stop);
    }
    /* 计算父进程的总时间 */
    printf("Parent Done. \n");
    stop = times(&buffer);
    tell_times(&buffer, start, stop);
    return 0;
}
void work(int k)       /* 模拟工作 */
{
    FILE *f;
    int i;
    double x=4.5;
    f = tmpfile();
    for(i = 0; i < k*100000; i++){
        fprintf(f,"Do some output\n");
        if(ferror(f)){
            fprintf(stderr,"Error writing to temorary file\n");
            exit(1);
        }
    }
    for(i=0;i<k*100000;i++)
        x=log(x*x+3.21);
}
void tell_times(struct tms *buf, clock_t start, clock_t stop)
{
    printf("stop time: %u,  total time: %d (ticks)\n",
            stop, stop-start);
    printf("          wall time: %lf(seconds)\n",
            (double)(stop - start)/(double)sysconf(_SC_CLK_TCK));
    printf("              utime: %d (ticks),  stime: %d (ticks)\n"
           "             cutime: %d (ticks), cstime: %d (ticks)\n",
           buf->tms_utime, buf->tms_stime, 
           buf->tms_cutime, buf->tms_cstime);
    printf("      user cpu time: %lf(seconds)\n",
           (double)(buf->tms_utime+buf->tms_cutime)
           /(double)sysconf(_SC_CLK_TCK));
    return;
}