term% cat index.txt CTIME(2) System Calls Manual CTIME(2)
NAME
ctime, localtime, gmtime, asctime, tm2sec, timezone - convert date and
time
SYNOPSIS
#include <u.h>
#include <libc.h>
char* ctime(long clock)
Tm* localtime(long clock)
Tm* gmtime(long clock)
char* asctime(Tm *tm)
long tm2sec(Tm *tm)
/env/timezone
DESCRIPTION
Ctime converts a time clock such as returned by time(2) into ASCII
(sic) and returns a pointer to a 30-byte string in the following form.
All the fields have constant width.
Wed Aug 5 01:07:47 EST 1973\n\0
Localtime and gmtime return pointers to structures containing the bro‐
ken-down time. Localtime corrects for the time zone and possible day‐
light savings time; gmtime converts directly to GMT. Asctime converts
a broken-down time to ASCII and returns a pointer to a 30-byte string.
typedef
struct {
int sec; /* seconds (range 0..59) */
int min; /* minutes (0..59) */
int hour; /* hours (0..23) */
int mday; /* day of the month (1..31) */
int mon; /* month of the year (0..11) */
int year; /* year A.D. - 1900 */
int wday; /* day of week (0..6, Sunday = 0) */
int yday; /* day of year (0..365) */
char zone[4]; /* time zone name */
int tzoff; /* time zone delta from GMT */
} Tm;
Tm2sec converts a broken-down time to seconds since the start of the
epoch. It ignores wday, and assumes the local time zone if zone is not
GMT.
When local time is first requested, the program consults the timezone
environment variable to determine the time zone and converts accord‐
ingly. (This variable is set at system boot time by init(8).) The
timezone variable contains the normal time zone name and its difference
from GMT in seconds followed by an alternate (daylight) time zone name
and its difference followed by a newline. The remainder is a list of
pairs of times (seconds past the start of 1970, in the first time zone)
when the alternate time zone applies. For example:
EST -18000 EDT -14400
9943200 25664400 41392800 57718800 ...
Greenwich Mean Time is represented by
GMT 0
SOURCE
/sys/src/libc/9sys
SEE ALSO
date(1), time(2), init(8)
BUGS
The return values point to static data whose content is overwritten by
each call.
Daylight Savings Time is ‘‘normal'' in the Southern hemisphere.
These routines are not equipped to handle non-ASCII text, and are
provincial anyway.
CTIME(2)