 |  |
|
Prototipurile functiilor de timp si data se gasesc in fisierul antet time.h. Tot in acest fisier sunt definite trei tipuri de reprezentare a timpului si date si doua macrocomenzi.
Cele trei structuri pentru reprezentarea datei si timpului sunt: tm, time_t si clock_t.
Tipul tm este definit astfel:
struct tm
tm este o structura care defineste timpul broken-down. Aceasta structura este utilizata de functiile: asctime, gmtime, localtime, mktime si strftime.
Tipul time_t reprezinta timpul si data sistemului ca un intreg. Acesta este denumit calendar time.
Tipul clock_t este returnat de functia clock si contine timpul scurs din momentul lansarii in executie a
programului. Timpul este masurat in impulsuri de ceas. Numarul de impulsuri pe
secunda este definit de
Pentru conversia timpului si datei intr-un sir de caractere exista doua functii si anume:
asctime - care converteste in zona indicata sub forma unui sir de 26 caractere timpul si data stocat intr-o structura. Prototipul functiei este:
char *asctime(const struct tm *tblock);
unde: tblock este zona in care se executa conversia datei si timpului.
ctime - care convertestevaloarea timpului intr-un sir de 26 caractere. Prototipul functiei este:
char *ctime(const time_t *time
unde : time este zona in care se obtine sirul prin conversia valorii timpului.
Sirul de 26 caractere obtinut prin conversie este terminat cu caracterul newline (n) si un caracter null (0) si are urmatorul format:
DDD MMM dd hh:mm:ss YYYY
unde:
DDD = Ziua (Mon, Tue, Wed, etc.)
MMM = Luna (Jan, Feb, Mar, etc.)
dd = Data (1, 2, , 31)
hh = Ora (1, 2, , 24)
mm = Minutele (1, , 59)
ss = Secundele (1, , 59)
YYYY = An
Spre exemplu:
Mon Oct 20 11:31:54 1952
Toate campurile au lungime
Valori returnate
Ambele functii returneaza un pointer spre sirul de caractere care contine data si timpul. Acest sir este o variabila statica, care este rescrisa de fiecare data cand se apeleaza functia.
Exemplu de utilizare a functiei asctime
#include <string.h>
#include <time.h>
#include <stdio.h>
int main(void)
Prin rularea acestui program se va afisa:
Thu Dec 22 09:30:01 2002
Exemplu de utilizare a functiei ctime
#include <stdio.h>
#include <time.h>
int main(void)
Prin rularea acestui program, rezultatul afisat apare sub forma:
Data si timpul sistemului este: Fri Jun 21 10:18:59 2002
Pentru a obtine timpul scurs de la 01/01/1970 se foloseste functia time, iar pentru a seta data si timpul sistemului se utilizeaza functia stime. Prototipurile functiilor sunt:
time_t time(time_t *timer
int stime(time_t *tp
Observatii
Functia time furnizeaza timpul, in secunde, scurs de la 1 ianuarie 19700 (00:00:00 GMT). Aceasta valoare este stocata in zona referita de *timer,
Functia stime seteaza data si timpul sistemului, masurat in secunde de la 01.01.197 (00:00:00 GMT). Variabila tp refera valoarea timpului exprimat in secunde.
Valori returnate
Functia time returneaza timpul scurs in secunde.
Functia stime returneaza 0.
Exemple
Exemplu pentru functia time
#include <time.h>
#include <stdio.h>
#include <dos.h>
int main(void)
La rularea acestui program, pe ecran se va afisa:
Exemplu pentru utilizarea functiei stime
#include <stdio.h>
#include <time.h>
int main(void)
La rularea acestui program, pe ecran se obtine:
Data curenta este: Sat Jun 22 11:57:55 2002
Noua data este Fri Jun 21 11:57:55 2002
gmtime, localtime <TIME.H>
gmtime converts date and time to Greenwich Mean Time (GMT)
localtime converts date and time to a structure
Declarations
struct tm *gmtime(const time_t *timer);
struct tm *localtime(const time_t *timer);
Remarks
Both functions accept the address of a value returned by time and return a pointer to a tm structure containing the broken-down time.
gmtime converts directly to GMT.
localtime corrects for the time zone and possible daylight saving time.
Arg What It Is/Does
timer Points to location of time_t value returned by time
Set timezone to the difference in seconds between GMT and local standard time.
In PST, timezone = 8(hrs) * 60(min/hr) * 60(sec/min)
timezone <TIME.H>
Difference in seconds between Greenwich Mean Time and local time.
Declaration: extern long timezone;
Remarks
Used by the time-and-date functions.
Set
daylight to non-zero if and only if the standard
daylight (global variable) <TIME.H>
Indicates whether Daylight Savings Time adjustments will occur
Declaration: extern int daylight;
Remarks
The time-and-date functions use daylight.
The ftime, localtime, and tzset functions set daylight to 1 or 0:
Value Meaning
Make Daylight Savings Time adjustments
Do not adjust for Daylight Savings Time
Return Value
gmtime and localtime return a pointer to the tm structure containing the broken-down time.
This structure is a static that is overwritten with each call.
/* gmtime example */
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <dos.h>
/* Pacific Standard Time & Daylight Savings */
char *tzstr = 'TZ=PST8PDT';
int main(void)
/* localtime example */
#include <time.h>
#include <stdio.h>
#include <dos.h>
int main(void)
mktime <TIME.H>
Converts time to calendar format
Declaration
time_t mktime(struct tm *t);
Remarks
Converts the time in the structure *t into a calendar time with the same format used by the time function.
The original values of the fields tm_sec, tm_min, tm_hour, tm_mday, and tm_mon are not restricted to the ranges described in the tm structure.
If the fields are not in their proper ranges, mktime adjusts them.
mktime computes values for the fields tm_wday and tm_yday after the other fields have been adjusted.
Return Value See Remarks.
/* mktime example */
#include <stdio.h>
#include <time.h>
char *wday[] = ;
int main(void)
strftime <TIME.H>
Formats time for output
Declaration
size_t _cdecl strftime(char *s, size_t maxsize, const char *fmt, const struct tm *t);
Remarks
strftime formats the time in *t into the array *s according to the format specifications (a format string) in *fmt.
All ordinary characters are copied unchanged. No more than maxsize characters are placed in s.
Return Value
On success, strftime returns the number of characters placed into s.
On error (if the number of characters required > maxsize), returns 0.
/* strftime example */
#include <stdio.h>
#include <time.h>
#include <dos.h>
int main(void)
clock <TIME.H>
Returns number of clock ticks since program start
Declaration
clock_t clock(void);
Remarks
clock can be used to determine the time interval between two events.
To determine the time in seconds, divide the value returned by clock by the value of the macro CLK_TCK.
Return Value
On success, returns the processor time elapsed since the beginning of the program invocation.
On failure (the processor time is not available, or its value can't be represented), returns -1.
/* clock example */
#include <time.h>
#include <stdio.h>
#include <dos.h>
int main(void)
difftime <TIME.H>
Computes difference between 2 times
Declaration
double difftime(time_t time2, time_t time1);
Remarks
difftime calculates the elapsed time in seconds, from time1 to time2.
Return Value
Returns the result of its calculation, as a double.
/* difftime example */
#include <time.h>
#include <stdio.h>
#include <dos.h>
#include <conio.h>
int main(void)
Converts current date to string.
Declaration: char *_strdate(char *buf);
Remarks
_strdate converts the current date to a string and stores the string in the buffer *buf.
The buffer must be at least 9 characters long.
The date string is terminated by a null character and has the form
MM/DD/YY
where
MM = month
DD = day
YY = year
MM, DD, and YY are all two-digit numbers.
Return Value: Returns buf, the address of the date string.
/* _strdate example */
#include <time.h>
#include <stdio.h>
void main(void)
Converts current time to string
Declaration: char *_strtime(char *buf);
Remarks
_strtime converts the current time to a string and stores the string in the buffer *buf.
The buffer must be at least 9 characters long.
The time string, terminated by a null character, has the form HH:MM:SS
where HH = hour MM = minute SS = seconds HH, MM, and SS are all two-digit numbers.
Return Value: Returns buf, the address of the time string.
/* __strtime example */
#include <time.h>
#include <stdio.h>
void main(void)
Acest document nu se poate descarca
| E posibil sa te intereseze alte documente despre: |
| Copyright © 2024 - Toate drepturile rezervate QReferat.com | Folositi documentele afisate ca sursa de inspiratie. Va recomandam sa nu copiati textul, ci sa compuneti propriul document pe baza informatiilor de pe site. { Home } { Contact } { Termeni si conditii } |
Documente similare:
|
Cauta document |