/** @file  ../include/time.h

@internalComponent

*/

/** @fn  asctime(const struct tm *tm)

@param tm

Refer to  ctime() for the documentation

@see gettimeofday()

@see getenv()

@see time()

@see tzset()

@publishedAll

@externallyDefinedApi

*/

/** @fn  clock(void)

@return   clock is just for build support and hence returns 0.

 The clock function

determines the amount of processor time used since the invocation of the

calling process, measured in CLOCKS_PER_SEC s of a second.

 Note: the clock system call eventually calls Symbian OS call user::GetCpuTime(), 

  which is not supported from version 8.0b, hence this api is included for build 

  support only.

@publishedAll

@externallyDefinedApi

*/

/** @fn  ctime(const time_t *clock)

@param clock

Note: This description also covers the following functions -

 difftime()  asctime()  localtime()  gmtime()  mktime()  ctime_r()  localtime_r()  gmtime_r()  asctime_r() 

@return   Each of these functions returns the value described, NULL, or -1 in the case of mktime if an error was detected.

  The functions ctime, gmtime and localtime all take as an argument a time value representing the time 

in seconds since the Epoch (00:00:00 UTC, January 1, 1970); see time

 The function localtime converts the time value pointed at by clock and returns a pointer to a " struct tm " (described below) which contains the broken down time information 

  for the value after adjusting for the current time zone (and any other factors 

  such as Daylight Saving Time). Time zone adjustments are performed as specified 

  by the TZ environment variable (see the tzset function). localtime uses tzset to initialize time conversion information 

  if tzset has not already been called by the process.

 After filling in the tm structure, localtime sets the tm_isdst's Nth element of tzname to a pointer to a ASCII string that is the time zone abbreviation to be

used with localtime's (return, value.);

 The function gmtime similarly converts the time value without any time zone adjustment 

  and returns a pointer to a tm structure (described below).

 The ctime function adjusts the time value for the current time zone, in 

  the same manner as localtime, and returns a pointer to a 26-character string of the form: Thu Nov 24 18:22:48 1986

\\0

 All the fields have constant width.

 The ctime_r function provides the same functionality as ctime except the caller must provide the output buffer buf to store the result, which must be at least 26 characters long.

 The localtime_r and gmtime_r functions provide the same functionality as localtime and gmtime respectively, except the caller must provide the output buffer result.

 The asctime function

converts the broken down time in the structure tm pointed at by *tm to the form

shown in the example above.

 The asctime_r function provides the same functionality as asctime except the caller provides the output buffer buf to store the result, which must be at least 26 characters long.

 The functions mktime converts the broken-down time in the structure pointed to by 

  tm into a time value with the same encoding as that of the values returned by 

  the time function (that is, seconds from the Epoch, UTC). The mktime function interprets the input structure according to the current 

  timezone setting (see tzset ).

 The original values of the tm_wday and tm_yday components of the structure are ignored, and the original values 

  of the other components are not restricted to their normal ranges and will be 

  normalized if needed. For example, October 40 is changed into November 9, a tm_hour of -1 means 1 hour before midnight, tm_mday of 0 means the day preceding the current month, and tm_mon of -2 means 2 months before January of tm_year.

 A positive or zero value for tm_isdst causes mktime to presume initially that summer time (for example, Daylight 

  Saving Time) is or is not in effect for the specified time.. A negative value 

  for tm_isdst causes the mktime function to attempt to define whether summer time is in effect 

  for the specified time. The tm_isdst and tm_gmtoff members are forced to zero by timegm.

 On successful completion, the values of the tm_wday and tm_yday components of the structure are set appropriately and the other 

  components are set to represent the specified calendar time, but with their 

  values forced to their normal ranges: The final value of tm_mday is not set until tm_mon and tm_year are determined.

 The mktime function returns the specified calendar time. If the calendar 

  time cannot be represented, it returns -1.

 The difftime function

returns the difference between two calendar times, ( time1 - time0), expressed in seconds.

 External declarations as well as the tm structure definition are in the 

@code

  #include <time.h> include file. The tm structure includes 

@endcode

  at least the following fields: 

@code

int tm_sec;		// seconds (0 - 60)

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;	// is summer time in effect? 

char *tm_zone;	// abbreviation of timezone name 

long tm_gmtoff;	// offset from UTC in seconds 

@endcode

 The

field tm_isdst is non-zero if summer time is in effect.

 The field tm_gmtoff is the offset (in seconds) of the time represented from UTC, with positive

values indicating east of the Prime Meridian.

Examples:

@code

//Example usage of asctime,localtime and gmtime:

#include <time.h>

#include <stdio.h>

int main(){

        time_t t;

        struct tm *timeptr;

        char* asc_time;

        t = time (NULL); //Get current time in seconds from Epoc

        //Fill tm struct w.r.t localtime using localtime

        timeptr = localtime (&t;);

        //Use this to convert it to a string indicating time w.r.t localtime

        asc_time = asctime (timeptr);

        printf ("Time from asctime w.r.t localtime : %s", asc_time);

        //Fill tm struct w.r.t GMT using gmtime

        timeptr = gmtime (&t;);

        //Use this to convert it to a string indicating time w.r.t GMT

        asc_time = asctime (timeptr);

        printf ("Time from asctime w.r.t gmtime : %s", asc_time);

        return 0;

}

@endcode

 Output

@code

Time from asctime w.r.t localtime : Thu Jun 22 10:42:27 2006

Time from asctime w.r.t gmtime : Thu Jun 22 05:12:27 2006

@endcode

@code

//Example usage of ctime,mktime:

#include <time.h>

#include <stdio.h>

int main(){

        time_t t;

        struct tm timeptr;

        char* c_time;

        //Fill the tm struct with values

        timeptr.tm_year = 2001;

        timeptr.tm_mon = 6;

        timeptr.tm_mday = 4;

        timeptr.tm_hour = 0;

        timeptr.tm_min = 0;

        timeptr.tm_sec = 1;

        timeptr.tm_isdst = -1;

        t = mktime (&timeptr;); //Call mktime to make time in seconds w.r.t epoc

        //Convert this to a string indicating time using ctime

        c_time = ctime (&t;);  

        printf ("Time from ctime : %s", c_time);

        return 0;

}

@endcode

 Output

@code

Time from ctime : Thu Jan  1 05:29:59 1970

@endcode

@code

//Example usage of difftime:

#include <time.h>

#include <unistd.h>

#include <stdio.h>

int main(){

        time_t t0,t1,t2;

        //Set initial and final values

        t0 = 10;

        t1 = 20;

        t2 = difftime (t1, t0); //Find the time difference using difftime

        printf ("Result of difftime = %d", t2);

        return 0;

}

@endcode

 Output

@code

Result of difftime = 10

@endcode

@see gettimeofday()

@see getenv()

@see time()

@see tzset()

Bugs:

 Except for difftime, mktime, and the _r variants of the other functions,

these functions leaves their result in an internal static object and return

a pointer to that object.

Subsequent calls to these

function will modify the same object. 

The C Standard provides no mechanism for a program to modify its current

local timezone setting, and the POSIX -standard method is not reentrant.

(However, thread-safe implementations are provided

in the POSIX threaded environment.) 

The tm_zone field of a returned tm

structure points to a static array of characters,

which will also be overwritten by any subsequent calls (as well as by

subsequent call to tzset ) 

@publishedAll

@externallyDefinedApi

*/

/** @fn  difftime(time_t time1, time_t time0)

@param time1

@param time0

Refer to  ctime() for the documentation

@see gettimeofday()

@see getenv()

@see time()

@see tzset()

@publishedAll

@externallyDefinedApi

*/

/** @fn  gmtime(const time_t *clock)

@param clock

Refer to  ctime() for the documentation

@see gettimeofday()

@see getenv()

@see time()

@see tzset()

@publishedAll

@externallyDefinedApi

*/

/** @fn  localtime(const time_t *clock)

@param clock

Refer to  ctime() for the documentation

@see gettimeofday()

@see getenv()

@see time()

@see tzset()

The localtime() is not guaranteed to be thread safe.

@publishedAll

@externallyDefinedApi

*/

/** @fn  mktime(struct tm *tm)

@param tm

Refer to  ctime() for the documentation

@see gettimeofday()

@see getenv()

@see time()

@see tzset()

@publishedAll

@externallyDefinedApi

*/

/** @fn  strftime(char *  s, size_t maxsize, const char *  format, const struct tm *  t)

@param s

@param maxsize

@param format

@param t

The strftime function formats the information from t into the buffer s according to the string pointed to by format .

The format string consists of zero or more conversion specifications and

ordinary characters.

All ordinary characters are copied directly into the buffer.

A conversion specification consists of a percent sign "\%"

and one other character.

No more than maxsize characters will be placed into the array. If the total number of resulting characters, including the terminating NULL character, is not more 

than maxsize , strftime returns the number of characters in the array, not counting 

the terminating NULL. Otherwise, zero is returned and the buffer contents are 

indeterminate.

@code

The conversion specifications are copied to the buffer after expansion as follows:- 

%A  is replaced by national representation of the full weekday name.  

%a  is replaced by national representation of the abbreviated weekday name.  

%B  is replaced by national representation of the full month name.  

%b  is replaced by national representation of the abbreviated month name.  

%C  is replaced by (year / 100) as decimal number; single digits are preceded by a zero.  

%c  is replaced by national representation of time and date.  

%D  is equivalent to "%m/%d/%y".  

%d  is replaced by the day of the month as a decimal number (01-31).  

%E* %O*  

  POSIX locale extensions. The sequences %Ec %EC %Ex %EX %Ey %EY %Od %Oe %OH %OI %Om %OM %OS %Ou %OU %OV %Ow %OW %Oy are supposed to provide alternate representations. 

Additionally %OB implemented to represent alternative months names (used standalone, without day mentioned). 

%e  is replaced by the day of month as a decimal number (1-31); single digits are preceded by a blank.  

%F  is equivalent to "%Y-%m-%d".  

%G  is replaced by a year as a decimal number with century. This year is the one that contains the greater part of the week (Monday as the first day of the week).  

%g  is replaced by the same year as in "%G", but as a decimal number without century (00-99).  

%H  is replaced by the hour (24-hour clock) as a decimal number (00-23).  

%h  the same as %b.  

%I  is replaced by the hour (12-hour clock) as a decimal number (01-12).  

%j  is replaced by the day of the year as a decimal number (001-366).  

%k  is replaced by the hour (24-hour clock) as a decimal number (0-23); single digits are preceded by a blank.  

%l  is replaced by the hour (12-hour clock) as a decimal number (1-12); single digits are preceded by a blank.  

%M  is replaced by the minute as a decimal number (00-59).  

%m  is replaced by the month as a decimal number (01-12).  

%n  is replaced by a newline.  

%O*  the same as %E*.  

%p  is replaced by national representation of either "ante meridiem" or "post meridiem" as appropriate.  

%R  is equivalent to "%H:%M".  

%r  is equivalent to "%I:%M:%S %p".  

%S  is replaced by the second as a decimal number (00-60).  

%s  is replaced by the number of seconds since the Epoch, UTC (see mktime).  

%T  is equivalent to "%H:%M:%S".  

%t  is replaced by a tab.  

%U  is replaced by the week number of the year (Sunday as the first day of the week) as a decimal number (00-53).  

%u  is replaced by the weekday (Monday as the first day of the week) as a decimal number (1-7).  

%V  is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (01-53). If the week containing January 1 has four or more days in the new year, then it is week 1; otherwise it is the last week of the previous year, and the next week is week 1.  

%v  is equivalent to "%e-%b-%Y".  

%W  is replaced by the week number of the year (Monday as the first day of the week) as a decimal number (00-53).  

%w  is replaced by the weekday (Sunday as the first day of the week) as a decimal number (0-6).  

%X  is replaced by national representation of the time.  

%x  is replaced by national representation of the date.  

%Y  is replaced by the year with century as a decimal number.  

%y  is replaced by the year without century as a decimal number (00-99).  

%Z  is replaced by the time zone name.  

%z  is replaced by the time zone offset from UTC; a leading plus sign stands for east of UTC, a minus sign for west of UTC, hours and minutes follow with two digits each and no delimiter between them (common form for RFC 822 date headers).  

%+  is replaced by national representation of the date and time (the format is similar to that produced by 'date( )' function ).  

%-*  GNU libc extension. Do not do any padding when performing numerical outputs.  

%_*  GNU libc extension. Explicitly specify space for padding.  

%0*  GNU libc extension. Explicitly specify zero for padding. 

%%  is replaced by ‘%’.  

@endcode

Examples:

@code

#include <string.h>

#include <stdio.h>

#include <time.h>

#include <locale.h>

int main()

{

   struct tm tm;

   char buf[255];

   char *locale;

   locale = setlocale(LC_TIME,"en_GB.ISO-8859-1");

   if( locale != NULL)

   {

       strptime("2001-11-12 18:31:01", "%Y-%m-%d %H:%M:%S", &tm;);

       printf("sec = %d min = %d hours = %d 

Year = %d Month = %d day = %d

",\

       tm.tm_sec,tm.tm_min,tm.tm_hour,tm.tm_year,tm.tm_mon,tm.tm_mday);

       strftime(buf, sizeof(buf), "%d %B %Y %H:%M:%S", &tm;);

       puts(buf);

       strptime("Mon","%a", &tm;);

       strftime(buf, sizeof(buf), "%a", &tm;);

       puts(buf);

    }

    else

       printf("Failed to set locale

");

}

@endcode

 Output

@code

sec = 1 min = 31 hours = 18

Year = 101 Month = 10 day = 12

12 November 2001 18:31:01

Mon

@endcode

@see printf()

@see ctime()

@see strptime()

@see wcsftime()

@publishedAll

@externallyDefinedApi

*/

/** @fn  time(time_t *p)

@param p

@return   On success the value of time in seconds since the Epoch is returned. On error 

(time_t)(-1) is returned and errno is set appropriately.

  The time function returns the value of time in seconds since 0 hours, 0 

minutes, 0 seconds, January 1, 1970, Coordinated Universal Time. If an error occurs, time returns the value ( time_t)(-1) .

 The return value is also stored in * p ,

provided that p is non-null.

Examples:

@code

/*

 * Detailed description : sample usage of time system call

 */

#include <time.h>

int main()

{

  time_t Time ;

  if(time(&Time;) < 0 ) 

  {

    printf("Time system call failed 

") ;

    return -1 ;

  }

 printf("Time value is %u 

" , Time) ;

 return 0 ;

}

@endcode

 Output

@code 

Time value is 1176916948

@endcode

@see gettimeofday()

@see ctime()

Bugs:

 Neither -isoC-99 nor -p1003.1-2001 requires time to set errno on failure; thus, it is impossible for an application to distinguish

the valid time value -1 (representing the last UTC second of 1969)

from the error return value. 

Systems conforming to earlier versions of the C and POSIX standards (including older versions of )

did not set * p in the error case. 

@publishedAll

@externallyDefinedApi

*/

/** @fn  tzset(void)

  The tzset function

initializes time conversion information used by the library routine localtime .

The environment variable TZ specifies how this is done.

 If TZ does not appear in the environment, the best available approximation 

  to local wall clock time is used.

 If TZ appears in the environment but its value is a null string, Coordinated

Universal Time ( UTC )

is used (without leap second correction).

Examples:

@code

#include <time.h>

#include <stdio.h>

int main(){

        time_t t;

        char* c_time;

        tzset(); //Call tzset

        c_time = ctime (&t;); //Get time-string using ctime for Epoc time

        printf ("Time from ctime after tzset: %s", c_time);

        return 0;

}

@endcode

 Output

@code

Time from ctime after tzset: Sun Apr  7 02:24:08 1974

@endcode

@see gettimeofday()

@see ctime()

@see getenv()

@see time()

@see gettimeofday()

@see ctime()

@see getenv()

@see time()