CTIME(3C-SVR3)      RISC/os Reference Manual       CTIME(3C-SVR3)



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

SYNOPSIS
     #include <sys/types.h>
     #include <time.h>

     char *ctime (clock)
     timet *clock;

     struct tm *localtime (clock)
     timet *clock;

     struct tm *gmtime (clock)
     timet *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,
     representing the time in seconds since 00:00:00 GMT, January
     1, 1970, and returns a pointer to a 26-character string in
     the following form.  All the fields have constant width.

          Sun Sep 16 01:03:52 1985\n\0

     localtime and gmtime return pointers to ``tm'' structures,
     described below.  localtime corrects for the time zone and
     possible Daylight Savings Time; gmtime converts directly to
     Greenwich Mean Time (GMT), which is the time the UNIX 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) */



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CTIME(3C-SVR3)      RISC/os Reference Manual       CTIME(3C-SVR3)



                  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;
          };

     tm_isdst 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 if and 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
     necessary, 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 New Jersey would be
     EST5EDT.  The effects of setting TZ are thus to change the
     values of the external variables timezone and daylight; in
     addition, the time zone names contained in the external
     variable

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

     are set 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.

     Note that in most installations, TZ is set by default when
     the user logs on, to a value in the local /etc/profile file
     [see profile(4)].

SEE ALSO
     time(2), getenv(3C), profile(4), environ(5).

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







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