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CTIME
!!!CTIME
NAME
SYNOPSIS
DESCRIPTION
CONFORMING TO
SEE ALSO
----
!!NAME


asctime, ctime, gmtime, localtime, mktime - transform binary date and time to ASCII
!!SYNOPSIS


__#include
__''timeptr''__);
char *ctime(const time_t *__''timep''__);
struct tm *gmtime(const time_t *__''timep''__);
struct tm *localtime(const time_t *__''timep''__);
time_t mktime(struct tm *__''timeptr''__);
extern char *__''tzname''__[[2];
long int__ ''timezone''__;
extern int__ ''daylight''__;
__
!!DESCRIPTION


The __ctime()__, __gmtime()__ and __localtime()__
functions all take an argument of data type ''time_t''
which represents calendar time. When interpreted as an
absolute time value, it represents the number of seconds
elapsed since 00:00:00 on January 1, 1970, Coordinated
Universal Time (UTC).


The __asctime()__ and __mktime()__ functions both take
an argument representing broken-down time which is a binary
representation separated into year, month, day, etc.
Broken-down time is stored in the structure ''tm'' which
is defined in '''' as follows:


struct tm
{
int     tm_sec;         /* seconds */
int     tm_min;         /* minutes */
int     tm_hour;        /* hours */
int     tm_mday;        /* day of the month */
int     tm_mon;         /* month */
int     tm_year;        /* year */
int     tm_wday;        /* day of the week */
int     tm_yday;        /* day in the year */
int     tm_isdst;       /* daylight saving time */
};


The members of the ''tm'' structure are:


''tm_sec''


The number of seconds after the minute, normally in the
range 0 to 59, but can be up to 61 to allow for leap
seconds.


''tm_min''


The number of minutes after the hour, in the range 0 to
59.


''tm_hour''


The number of hours past midnight, in the range 0 to
23.


''tm_mday''


The day of the month, in the range 1 to 31.


''tm_mon''


The number of months since January, in the range 0 to
11.


''tm_year''


The number of years since 1900.


''tm_wday''


The number of days since Sunday, in the range 0 to
6.


''tm_yday''


The number of days since January 1, in the range 0 to
365.


''tm_isdst''


A flag that indicates whether daylight saving time is in
effect at the time described. The value is positive if
daylight saving time is in effect, zero if it is not, and
negative if the information is not available.


The __ctime()__ function converts the calendar time
''timep'' into a string of the form




The abbreviations for the days of the week are `Sun', `Mon',
`Tue', `Wed', `Thu', `Fri', and `Sat'. The abbreviations for
the months are `Jan', `Feb', `Mar', `Apr', `May', `Jun',
`Jul', `Aug', `Sep', `Oct', `Nov', and `Dec'. The return
value points to a statically allocated string which might be
overwritten by subsequent calls to any of the date and time
functions. The function also sets the external variable
''tzname'' with information about the current time
zone.


The __gmtime()__ function converts the calendar time
''timep'' to broken-down time representation, expressed
in Coordinated Universal Time (UTC).


The __localtime()__ function converts the calendar time
''timep'' to broken-time representation, expressed
relative to the user's specified time zone. The function
sets the external variables ''tzname'' with information
about the current time zone, ''timezone'' with the
difference between Coordinated Universal Time (UTC) and
local standard time in seconds, and ''daylight'' to a
non-zero value if standard US daylight savings time rules
apply.


The __asctime()__ function converts the broken-down time
value ''timeptr'' into a string with the same format as
__ctime()__. The return value points to a statically
allocated string which might be overwritten by subsequent
calls to any of the date and time functions.


The __mktime()__ function converts a broken-down time
structure, expressed as local time, to calendar time
representation. The function ignores the specified contents
of the structure members ''tm_wday'' and ''tm_yday''
and recomputes them from the other information in the
broken-down time structure. If structure members are outside
their legal interval, they will be normalized (so that,
e.g., 40 October is changed into 9 November). Calling
__mktime()__ also sets the external variable
''tzname'' with information about the current time zone.
If the specified broken-down time cannot be represented as
calendar time (seconds since the epoch), __mktime()__
returns a value of (time_t)(-1) and does not alter the
''tm_wday'' and ''tm_yday'' members of the broken-down
time structure.
!!CONFORMING TO


SVID 3, POSIX, BSD 4.3, ISO 9899
!!SEE ALSO


date(1), gettimeofday(2), time(2),
tzset(3), difftime(3),
strftime(3).
----
12 pages link to ctime(3):
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Last edited on Tuesday, June 4, 2002 12:24:15 am by "perry"
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