from robert

[unix-history] / usr / src / lib / libc / gen / timezone.c

/* @(#)timezone.c       4.2 (Berkeley) %G% */
/*
* The arguments are the number of minutes of time
* you are westward from Greenwich and whether DST is in effect.
* It returns a string
* giving the name of the local timezone.
*
* Sorry, I don't know all the names.
*/

static struct zone {
       int     offset;
       char    *stdzone;
       char    *dlzone;
} zonetab[] = {
       4*60, "AST", "ADT",             /* Atlantic */
       5*60, "EST", "EDT",             /* Eastern */
       6*60, "CST", "CDT",             /* Central */
       7*60, "MST", "MDT",             /* Mountain */
       8*60, "PST", "PDT",             /* Pacific */
       0, "GMT", 0,                    /* Greenwich */
       -10*60, "EST", "EST",           /* Aust: Eastern */
       -10*60+30, "CST", "CST",        /* Aust: Central */
       -8*60, "WST", 0,                /* Aust: Western */
       -1
};

char *timezone(zone, dst)
{
       register struct zone *zp;
       static char czone[10];
       char *sign;
       register char *p, *q;
       char *getenv(), *index();

       if (p = getenv("TZNAME")) {
               if (q = index(p, ',')) {
                       if (dst)
                               return(++q);
                       else {
                               *q = '\0';
                               strncpy(czone, p, sizeof(czone)-1);
                               czone[sizeof(czone)-1] = '\0';
                               *q = ',';
                               return (czone);
                       }
               }
               return(p);
       }
       for (zp=zonetab; zp->offset!=-1; zp++)
               if (zp->offset==zone) {
                       if (dst && zp->dlzone)
                               return(zp->dlzone);
                       if (!dst && zp->stdzone)
                               return(zp->stdzone);
               }
       if (zone<0) {
               zone = -zone;
               sign = "+";
       } else
               sign = "-";
       sprintf(czone, "GMT%s%d:%02d", sign, zone/60, zone%60);
       return(czone);
}