ctime(3C) — sys5



CTIME(3C)       DOMAIN/IX Reference Manual (SYS5)       CTIME(3C)



NAME
     ctime, localtime, gmtime, asctime, tzset - convert date and
     time to string

USAGE
     #include <time.h>

     char *ctime (clock)
     long *clock;

     struct tm *localtime (clock)
     long *clock;

     struct tm *gmtime (clock)
     long *clock;

     char *asctime (tm)
     struct tm *tm;

     extern long timezone;

     extern int daylight;

     extern char *tzname[2];

     void tzset ( )

DESCRIPTION
     Ctime converts a long integer (pointed to by clock) that
     represents the time in seconds since 00:00:00 GMT, January
     1, 1970.  Ctime then returns a pointer to a 26-character
     string in the following form.  (All the fields have constant
     width.)

          Sun Sep 16 01:03:52 1973\n\0

     Localtime and gmtime return pointers to ``tm'' structures,
     described below.  Localtime corrects for the time zone and
     for Daylight Savings Time, if necessary; gmtime converts
     directly to Greenwich Mean Time (GMT), which is the time the
     DOMAIN/IX system uses.

     Asctime converts a ``tm'' structure to a 26-character
     string, as shown in the above example, and returns a pointer
     to the string.

     Declarations of all the functions and externals, and the
     ``tm'' structure, are in the <time.h> header file.  The
     structure declaration is:

          struct tm {
                  int tm_sec; /* seconds (0 - 59) */



Printed 5/10/85                                           CTIME-1



CTIME(3C)       DOMAIN/IX Reference Manual (SYS5)       CTIME(3C)



                  int tm_min; /* minutes (0 - 59) */
                  int tm_hour;     /* hours (0 - 23) */
                  int tm_mday;     /* day of month (1 - 31) */
                  int tm_mon; /* month of year (0 - 11) */
                  int tm_year;     /* year - 1900 */
                  int tm_wday;     /* day of week (Sunday = 0) */
                  int tm_yday;     /* day of year (0 - 365) */
                  int tm_isdst;
          };

     Tmisdst is non-zero if Daylight Savings Time is in effect.

     The external long variable timezone contains the difference,
     in seconds, between GMT and local standard time (in EST,
     timezone is 5*60*60); the external variable daylight is
     non-zero only if the standard U.S.A.  Daylight Savings Time
     conversion should be applied.  The program knows about the
     peculiarities of this conversion in 1974 and 1975; if neces-
     sary, a table for these years can be extended.

     If an environment variable named TZ is present, asctime uses
     the contents of the variable to override the default time
     zone.  The value of TZ must be a three-letter time zone
     name, followed by a number representing the difference
     between local time and Greenwich Mean Time in hours, fol-
     lowed by an optional three-letter name for a daylight time
     zone.  For example, the setting for Massachusetts would be
     EST5EDT.  Setting TZ thus changes the values of the external
     variables timezone and daylight; it also sets the time zone
     names contained in the external variable

          char *tzname[2] = { "EST", "EDT" };

     from the environment variable TZ.  The function tzset sets
     these external variables from TZ; tzset is called by asctime
     and may also be called explicitly by the user.

     TZ is set by default when the user logs on, to a value in
     the local /etc/profile file.

NOTES
     The return values point to static data whose content is
     overwritten by each call.

RELATED INFORMATION
     time(2), getenv(3C), environ(5)









CTIME-2                                           Printed 5/10/85

Museum