计算时间差

[梦想一米七八]

获取系统当前的时间，然后怎么计算时间差，让用户在规定时间内答题，时间到则终止答题

[NexTor]

感觉直接用定时器做就好了，答题开始的时候将定时器打开，时间到了就跳转结束界面

[老夏]

如楼上，定时器对于这个应用场景够用了，不用特别精确

[赵4老师]

仅供参考：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef WIN32
    #include <windows.h>
    #include <io.h>
    #include <process.h>
    #define  MYVOID             void
#else
    #include <unistd.h>
    #include <sys/time.h>
    #include <pthread.h>
    #define  CRITICAL_SECTION   pthread_mutex_t
    #define  _vsnprintf         vsnprintf
    #define  MYVOID             void *
#endif
//Log{
#define MAXLOGSIZE 20000000
#define ARRSIZE(x) (sizeof(x)/sizeof(x[0]))
#include <time.h>
#include <sys/timeb.h>
#include <stdarg.h>
char logfilename1[]="MyLog1.log";
char logfilename2[]="MyLog2.log";
char logstr[16000];
char datestr[16];
char timestr[16];
char mss[4];
CRITICAL_SECTION cs_log;
FILE *flog;
#ifdef WIN32
void Lock(CRITICAL_SECTION *l) {
    EnterCriticalSection(l);
}
void Unlock(CRITICAL_SECTION *l) {
    LeaveCriticalSection(l);
}
void sleep_ms(int ms) {
    Sleep(ms);
}
#else
void Lock(CRITICAL_SECTION *l) {
    pthread_mutex_lock(l);
}
void Unlock(CRITICAL_SECTION *l) {
    pthread_mutex_unlock(l);
}
void sleep_ms(int ms) {
    usleep(ms*1000);
}
#endif
void LogV(const char *pszFmt,va_list argp) {
    struct tm *now;
    struct timeb tb;


    if (NULL==pszFmt||0==pszFmt[0]) return;
    if (-1==_vsnprintf(logstr,ARRSIZE(logstr),pszFmt,argp)) logstr[ARRSIZE(logstr)-1]=0;
    ftime(&tb);
    now=localtime(&tb.time);
    sprintf(datestr,"%04d-%02d-%02d",now->tm_year+1900,now->tm_mon+1,now->tm_mday);
    sprintf(timestr,"%02d:%02d:%02d",now->tm_hour     ,now->tm_min  ,now->tm_sec );
    sprintf(mss,"%03d",tb.millitm);
    printf("%s %s.%s %s",datestr,timestr,mss,logstr);
    flog=fopen(logfilename1,"a");
    if (NULL!=flog) {
        fprintf(flog,"%s %s.%s %s",datestr,timestr,mss,logstr);
        if (ftell(flog)>MAXLOGSIZE) {
            fclose(flog);
            if (rename(logfilename1,logfilename2)) {
                remove(logfilename2);
                rename(logfilename1,logfilename2);
            }
            flog=fopen(logfilename1,"a");
            if (NULL==flog) return;
        }
        fclose(flog);
    }
}
void Log(const char *pszFmt,...) {
    va_list argp;

    Lock(&cs_log);
    va_start(argp,pszFmt);
    LogV(pszFmt,argp);
    va_end(argp);
    Unlock(&cs_log);
}
//Log}
int No_Loop=0;
MYVOID testThread(void *pcn) {
    int n,i;

    n=(int)pcn;
    i=0;
    while (1) {
        sleep_ms(1000);
        Log("in testThread %d:i==%ds\n",n,++i);
        if (i>=5) No_Loop=1;
    }
}
int main(int argc,char * argv[]) {
    int i;
#ifdef WIN32
    InitializeCriticalSection(&cs_log);
#else
    pthread_mutex_init(&cs_log,NULL);
    pthread_t threads[1];
    int threadsN;
    int rc;
#endif
    Log("=========BEGIN==================\n");
#ifdef WIN32
    _beginthread((void(__cdecl *)(void *))testThread,0,(void *)1);
#else
    threadsN=0;
    rc=pthread_create(&(threads[threadsN++]),NULL,testThread,(void *)1);if (rc) Log("%d=pthread_create %d error!\n",rc,threadsN-1);
#endif
    i=0;
    while (1) {
        sleep_ms(100);
        Log("in main:i==%d\n",++i);
        if (No_Loop==1) break;//
    }
    Log("=========END====================\n");
#ifdef WIN32
    DeleteCriticalSection(&cs_log);
#else
    pthread_mutex_destroy(&cs_log);
#endif
    return 0;
}
//2012-06-14 16:27:21.500 =========BEGIN==================
//2012-06-14 16:27:21.609 in main:i==1
//2012-06-14 16:27:21.718 in main:i==2
//2012-06-14 16:27:21.828 in main:i==3
//2012-06-14 16:27:21.937 in main:i==4
//2012-06-14 16:27:22.046 in main:i==5
//2012-06-14 16:27:22.156 in main:i==6
//2012-06-14 16:27:22.265 in main:i==7
//2012-06-14 16:27:22.375 in main:i==8
//2012-06-14 16:27:22.484 in main:i==9
//2012-06-14 16:27:22.500 in testThread 1:i==1s
//2012-06-14 16:27:22.593 in main:i==10
//2012-06-14 16:27:22.703 in main:i==11
//2012-06-14 16:27:22.812 in main:i==12
//2012-06-14 16:27:22.921 in main:i==13
//2012-06-14 16:27:23.031 in main:i==14
//2012-06-14 16:27:23.140 in main:i==15
//2012-06-14 16:27:23.250 in main:i==16
//2012-06-14 16:27:23.359 in main:i==17
//2012-06-14 16:27:23.468 in main:i==18
//2012-06-14 16:27:23.500 in testThread 1:i==2s
//2012-06-14 16:27:23.578 in main:i==19
//2012-06-14 16:27:23.687 in main:i==20
//2012-06-14 16:27:23.796 in main:i==21
//2012-06-14 16:27:23.906 in main:i==22
//2012-06-14 16:27:24.015 in main:i==23
//2012-06-14 16:27:24.125 in main:i==24
//2012-06-14 16:27:24.234 in main:i==25
//2012-06-14 16:27:24.343 in main:i==26
//2012-06-14 16:27:24.453 in main:i==27
//2012-06-14 16:27:24.500 in testThread 1:i==3s
//2012-06-14 16:27:24.562 in main:i==28
//2012-06-14 16:27:24.671 in main:i==29
//2012-06-14 16:27:24.781 in main:i==30
//2012-06-14 16:27:24.890 in main:i==31
//2012-06-14 16:27:25.000 in main:i==32
//2012-06-14 16:27:25.109 in main:i==33
//2012-06-14 16:27:25.218 in main:i==34
//2012-06-14 16:27:25.328 in main:i==35
//2012-06-14 16:27:25.437 in main:i==36
//2012-06-14 16:27:25.500 in testThread 1:i==4s
//2012-06-14 16:27:25.546 in main:i==37
//2012-06-14 16:27:25.656 in main:i==38
//2012-06-14 16:27:25.765 in main:i==39
//2012-06-14 16:27:25.875 in main:i==40
//2012-06-14 16:27:25.984 in main:i==41
//2012-06-14 16:27:26.093 in main:i==42
//2012-06-14 16:27:26.203 in main:i==43
//2012-06-14 16:27:26.312 in main:i==44
//2012-06-14 16:27:26.421 in main:i==45
//2012-06-14 16:27:26.500 in testThread 1:i==5s
//2012-06-14 16:27:26.531 in main:i==46
//2012-06-14 16:27:26.531 =========END====================

[sevancheng]

GetTickCount()
time(NILL)
CTime::GetCurrentTime()
ColeDataTime::GetCurrentTime()

[AlbertS]

看你的操作系统了，
我感觉使用time(NULL)应该就可以

[zhongchengli]

获取系统当前时间可以修改，用定时器

[zhouqunhai]

time-t ts;
......

[棉猴]

使用定时器就可以吧