Listing 1 time1.c - 采用不同格式输出当前的日期和时间
#include <stdio.h>
#include <time.h>
#define BUFSIZE 128
main()
{
time_t tval;
struct tm *now;
char buf[BUFSIZE];
char *fancy_format =
"Or getting really fancy:\n"
"%A, %B %d, day %j of %Y.\n"
"The time is %I:%M %p.";
/* Get current date and time */
tval = time(NULL);
now = localtime(&tval);
printf("The current date and time:\n"
"%d/%02d/%02d %d:%02d:%02d\n\n",
now->tm_mon+1, now->tm_mday, now->tm_year,
now->tm_hour, now->tm_min, now->tm_sec);
printf("Or in default system format:\n%s\n",
ctime(&tval));
strftime(buf,sizeof buf,fancy_format,now);
puts(buf);
return 0;
}
/* Output
The current date and time:
10/06/92 12:58:00
Or in default system format:
Tue Oct 06 12:58:00 1992
Or getting really fancy:
Tuesday, October 06, day 280 of 1992.
The time is 12:58 PM.
*/
/* End of File */
Listing 2 time2.c -展示如何计算将来某一天的日期以及以秒为单位计算出的执行时间
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
main()
{
time_t start, stop;
struct tm *now;
int ndays;
/* Get current date and time */
time(&start);
now = localtime(&start);
/* Enter an interval in days */
fputs("How many days from now? ",stderr);
if (scanf("%d",&ndays) !=1)
return EXIT_FAILURE;
now->tm_mday += ndays;
if (mktime(now) != -1)
printf("New date: %s",asctime(now));
else
puts("Sorry. Can't encode your date.");
/* Calculate elapsed time */
time(&stop);
printf("Elapsed program time in seconds: %f\n",
difftime(stop,start));
return EXIT_SUCCESS;
}
/* Output
How many days from now? 45
New date: Fri Nov 20 12:40:32 1992
Elapsed program time in seconds: 1.000000
*/
/* End of File */
Listing 3 date.h - 一个简单的日期结构
struct Date
{
int day;
int month;
int year;
};
typedef struct Date Date;
Date* date_interval(const Date *, const Date *);
/* End of File */
Listing 4 date_int.c - 计算两个日期的间隔
/* date_int.c: Compute duration between two dates */
#include "date.h"
#define isleap(y) \
((y)%4 == 0 && (y)%100 != 0 || (y)%400 == 0)
static int Dtab [2][13] =
{
{0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},
{0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}
};
Date *date_interval(const Date *d1, const Date *d2)
{
static Date result;
int months, days, years, prev_month;
/* Compute the interval - assume d1 precedes d2 */
years = d2->year - d1->year;
months = d2->month - d1->month;
days = d2->day - d1->day;
/* Do obvious corrections (days before months!)
*
* This is a loop in case the previous month is
* February, and days < -28.
*/
prev_month = d2->month - 1;
while (days < 0)
{
/* Borrow from the previous month */
if (prev_month == 0)
prev_month = 12;
--months;
days += Dtab[isleap(d2->year)][prev_month--];
}
if (months < 0)
{
/* Borrow from the previous year */
--years;
months += 12;
}
/* Prepare output */
result.month = months;
result.day = days;
result.year = years;
return &result;
}
/* End of File */
Listing 5 tdate.c - 举例说明日期间隔函数的使用
/* tdate.c: Test date_interval() */
#include <stdio.h>
#include <stdlib.h>
#include "date.h"
main()
{
Date d1, d2, *result;
int nargs;
/* Read in two dates - assume 1st precedes 2nd */
fputs("Enter a date, MM/DD/YY> ",stderr);
nargs = scanf("%d/%d/%d%*c", &d1.month,
&d1.day, &d1.year);
if (nargs != 3)
return EXIT_FAILURE;
fputs("Enter a later date, MM/DD/YY> ",stderr);
nargs = scanf("%d/%d/%d%*c", &d2.month,
&d2.day, &d2.year);
if (nargs != 3)
return EXIT_FAILURE;
/* Compute interval in years, months, and days */
result = date_interval(&d1, &d2);
printf("years: %d, months: %d, days: %d\n",
result->year, result->month, result->day);
return EXIT_SUCCESS;
}
/* Sample Execution:
Enter a date, MM/DD/YY> 10/1/51
Enter a later date, MM/DD/YY> 10/6/92
years: 41, months: 0, days: 5 */
/* End of File */
Listing 6 ftime.c - 确定是否time1.c比time2.c更新
/* ftime.c: Compare file time stamps */
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <time.h>
main()
{
struct stat fs1, fs2;
if (stat("time1.c",&fs1) == 0 &&
stat("time2.c",&fs2) == 0)
{
double interval =
difftime(fs2.st_mtime,fs1.st_mtime);
printf("time1.c %s newer than time2.c\n",
(interval < 0.0) ? "is" : "is not");
return EXIT_SUCCESS;
}
else
return EXIT_FAILURE;
}
/* Output
time1.c is not newer than time2.c */
/* End of File */
Listing 7 touch.c -通过覆盖旧文件或者创建一个新的文件来更新时间戳
/* touch.c: Update a file's time stamp */
#include <stdio.h>
void touch(char *fname)
{
FILE *f = fopen(fname,"r+b");
if (f != NULL)
{
char c = getc(f);
rewind(f);
putc(c,f);
}
else
fopen(fname,"wb");
fclose(f);
}
/* End of File */
