时间

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shell操作时间

  1 date        #查看或者设置系统时钟                                                                                                                                2 cal          3 ncal  4 calendar  5 time cal<span style="font-size:14px;color:#333333;background-color:#FFFFFF;line-height:25px;white-space:pre-wrap;">system-config-date       #图形化修改</span>hwclock           #硬件时间 查看设置与同步

</pre></p><p></p><p>1，获取和转换日期时间（Calendar Time）</p><p>系统调用：gettimeofday(),time(),ctime(),gmtime(),localtime(),mktime(),asctime().</p><p><pre name="code" class="objc"> 19 #include <locale.h> 20 #include <time.h> 21 #include <sys/time.h> 22 #include <stdio.h> 23 #include <stdlib.h> 24 #define SECONDS_IN_TROPICAL_YEAR (365.24219*24*60*60) 25 #define S_Y SECONDS_IN_TROPICAL_YEAR 26  27 int  28 main(int argc,char *argv[]) 29 { 30     time_t t; 31     struct tm *gmp, *locp; 32     struct tm gm,loc; 33     struct timeval tv; 34  35     t = time(NULL); 36     printf("Seconds since the Epoch(1 Jan 1970):%ld\t", (long)t); 37     printf("(about %6.3f years)\n", t/S_Y); 38  39     if (gettimeofday(&tv, NULL) == -1) 40       exit(EXIT_FAILURE); 41     printf("    gettimeofday() return %ld secs,%ld microsecs\n",  42                 (long) tv.tv_sec, (long) tv.tv_usec); 43  44     gmp = gmtime(&t);                                                                                                                     45     if (gmp == NULL) 46       exit(-1); 47     gm = *gmp;    /*save local copy, since *gmp may be modified by asctime() or gmtime() */ 48     printf("Broken down by gmtime():\n"); 49     printf("    year:mon:mday:hour:min:sec = %d %d %d %d %d %d %d\t",  50                 gm.tm_year, gm.tm_mon, gm.tm_mday, gm.tm_hour, gm.tm_min, gm.tm_sec); 51     printf("wday:yday:isdst = %d %d %d\n", 52                 gm.tm_wday, gm.tm_yday, gm.tm_isdst); 53  54     locp = localtime(&t); 55     if (locp == NULL) 56       exit(-1); 57     loc = *locp;    /*save local copy*/ 58     printf("Broken down by localtime():\n"); 59     printf("    year:mon:mday:hour:min:sec = %d %d %d %d %d %d %d\t",  60                 loc.tm_year, loc.tm_mon, loc.tm_mday, loc.tm_hour, loc.tm_min, loc.tm_sec); 61     printf("wday:yday:isdst = %d %d %d\n", 62                 loc.tm_wday, loc.tm_yday, loc.tm_isdst); 63  64     printf("asctime() formats the gmtime() value as:%s", asctime(&gm)); 65     printf("ctime() formats the time() value as:    %s", ctime(&t)); 66  67     printf("mktime() of gmtime() value:    %ld secs\n", (long)mktime(&gm)); 68     printf("mktime() of localtime() value: %ld secs\n", (long)mktime(&loc)); 69     return 0; 70 } 71 #output Seconds since the Epoch(1 Jan 1970):1458092949    (about 46.205 years)    gettimeofday() return 1458092949 secs,76250 microsecsBroken down by gmtime():    year:mon:mday:hour:min:sec = 116 2 16 1 49 9 -1437482552    wday:yday:isdst = 3 75 0Broken down by localtime():    year:mon:mday:hour:min:sec = 116 2 16 9 49 9 -1437482552    wday:yday:isdst = 3 75 0asctime() formats the gmtime() value as:Wed Mar 16 01:49:09 2016ctime() formats the time() value as:    Wed Mar 16 09:49:09 2016mktime() of gmtime() value:    1458064149 secsmktime() of localtime() value: 1458092949 secs

2、返回当前时间的字符串

系统调用：strftime(),currTime()

#include <time.h>#include <stdio.h>#include <stdlib.h>#define BUF_SIZE 1000char *currTime(const char *format){    static char buf[BUF_SIZE];    /* Nonreentrant*/    time_t t;    size_t s;    struct tm *tm;    t = time(NULL);    tm = localtime(&t);    if (tm == NULL)      return NULL;    s = strftime(buf, BUF_SIZE, (format != NULL) ? format : "%c", tm);    return (s == 0) ? NULL : buf;}

3、获取和转换日历时间

系统调用：strptime（）

 19 #define _XOPEN_SOURCE 20 #include <time.h> 21 #include <locale.h> 22 #include <stdlib.h> 23 #include <stdio.h> 24  25 #define SBUF_SIZE 1000 26  27 int 28 main(int argc, char *argv[]) 29 { 30     struct tm tm; 31     char sbuf[SBUF_SIZE]; 32     char *ofmt; 33  34     if (argc < 3 || strcmp(argv[1], "--help") == 0){ 35         printf("%s input-date-time in-format [out-foramt]\n", argv[0]); 36         exit(-1); 37     } 38  39     if(setlocale(LC_ALL,"") ==NULL) 40       exit(-1); 41  42     memset(&tm, 0, sizeof(struct tm)); 43     if (strptime(argv[1],argv[2], &tm) == NULL) 44       exit(-1); 45  46     tm.tm_isdst = -1; 47     printf("calendar time (seconds since Epoch): %ld\n", (long) mktime(&tm)); 48  49     ofmt = (argc > 3) ? argv[3] :"%H:%M:%S %A, %d %B %Y %Z"; 50     if (strftime(sbuf, SBUF_SIZE, ofmt, &tm) == 0) 51       exit(-1); 52     printf("strftime() yields: %s\n", sbuf); 53  54     return 0; 55 }#output$ ./a.out  "9:39:46pm 1 Feb 2016" "%I:%M:%S%p %d %b %Y"calendar time (seconds since Epoch): 1454333986strftime() yields: 21:39:46 星期一, 01 二月 2016 CST$ ./a.out  "9:39:46pm 1 Feb 2016" "%I:%M:%S%p %d %b %Y" "%F %T"calendar time (seconds since Epoch): 1454333986strftime() yields: 2016-02-01 21:39:46

4，时区

系统调用：setlocale（），settimeofday（），adjtime（），

5、软件时钟

可配置的内核选项，常见的300赫兹可以被视频帧速度25帧每秒（PAL）和30（NTSC）整除，250赫兹（默认）

6、进程时间

系统调用：times（），clock（）。

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