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From: decot@hpisod2.HP.COM (Dave Decot)
Newsgroups: comp.lang.c
Subject: Re: struct tm -> time_t converter wanted
Message-ID: <2550079@hpisod2.HP.COM>
Date: 21 Oct 88 02:15:20 GMT
References: <442@grand.UUCP>
Organization: Hewlett Packard, Cupertino
Lines: 31

> I was surprised to find no routine in the C library
> to convert a struct tm into a time_t.  Is there
> such a routine floating around somewhere?

Probably, but if you're going to do one of these yourself, please do it
in the form described by ANSI C, so you can use that when you get an
ANSI compiler and libraries:

    #include <time.h>

    time_t mktime(timeptr)
    struct tm *timeptr;

    The mktime function converts the broken-down time, expressed as
    local time, in the structure pointed to by timeptr into a calendar
    time value with the same encoding as that of the values returned by
    the [time()] function.  The original values of the tm_wday and
    tm_yday components of the structure are ignored, and the original
    values of the other components are not restricted to the [normal
    ranges of those members].  On successful completion, the values of
    the tm_wday and tm_yday components of the structure are set
    appropriately, and the other components are set to represent the
    specified calendar time, but with their values forced [into the
    normal ranges]; the final value of tm_mday is not set until tm_mon and
    tm_year are determined.

    If the calendar time cannot be represented, the function returns the
    value (time_t)-1.

Dave Decot
decot@hpda