🚀 go-pugleaf

bernie@metapro.DIALix.oz.au (Bernd Felsche) writes:

>In <1992Jul16.145836.15586@avalon.nwc.navy.mil>
>   dejesus@archimedes.nwc.navy.mil (Francisco X DeJesus) writes:

>>If I can get today's date in a shell script or C program, how can I find
>>out the dates of the next week? For example, if I know today is
>>"Wed Dec 30 1992", how can I have the program now that the next seven days
>>are going to be "Thu Dec 31 1992", "Fri Jan 1 1993", etc (taking the
>>case in which both month and year could change).

>I usually get away with fiddling with the timezone.
>Unfortunately, some operating systems ignore hour offsets
>greater than 12 hours from UTC.

    ...The most reliable way to do this is to first convert the current
date/time into a time_t type ("time_t" is defined in the system header file
<time.h>, and is basically a long containing the number of seconds since the
start of 01 Jan 1970 on most systems):

       #include <time.h>

       time_t   current_time;

       current_time = time((time_t *)0);

    Having done this, just set a macro for the length (in seconds) of one
day:

       #define ONE_DAY	((60) * (60) * (24))

    From here, you can get the value for any day you want. For example, the 
value for two days' into the future would be:

      two_days_ahead = current_time + (ONE_DAY * 2);

    You can then convert the time_t for the desired day back into some 
useful structure. If you want to manipulate it, maybe do this:

      struct tm *timestruct;

      timestruct = localtime(&two_days_ahead);

    The function localtime() and the struct tm are both defined in <time.h>.
Struct tm includes separate values for year, month, etc, in case you want 
specific bits.

    If you just want to print it out, try this:

    struct tm *timestruct;
    char timestamp[30];

    timestruct = localtime(&two_days_ahead);

    strftime(timestamp, 30, "%a %b %d %H:%M:%S %Z %Y", timestruct);

    This will give you the string timestamp, which will have this format:

Tue Jul 28 07:19:53 GMT 1992

  Hope this is helpful. Cheers, Colin.



-- 
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Colin Lynch - Telecom Australia | E-mail:  colinl@cssc-syd.tansu.oz.au
Advanced Network Products       |   post:  PO Box A226
Customised Software             |          Sydney South NSW  2000