Thread: time function question

#include <time.h>
time_t now;
time_t *pNow;
now = time(pNow);

the system time is stored in the variable now and in the pointer pNow. You could use now or pnow alone if desired. Unfortunately time_t and time_t * are not convenient formats so you can convert them like this:

char sNow[30] = ctime(pnow);
tm tNow = localtime(pnow);


the char string returned by ctime() is something like:

Mon Dec 31, 2001

and tm is a struct something like this:

struct tm
{
int tm_month;
int tm_day;
int tm_year;
int day_of_week;
//etc.
}

Exact formats, prototypes, definitions, etc. should be available in the help section of your compiler.

Originally posted by Unregistered
#include <time.h>
time_t now;
time_t *pNow;
now = time(pNow);

Woah, is that an uninatialized pointer there? It looks like its pointing to nowhere, but then you pass it to the time function, which fills it in, so your filling up some random memory. Not cool

http://www.cppreference.com/stddate.html has a reference for all the time functions


The localtime function returns a struct that has a bunch of info
info here from http://www.devx.com/free/tips/tipvie...ontent_id=1810

struct tm
{
int tm_sec; // the number of elapsed seconds in the minute
int tm_min; // the number of elapsed minutes in the hour
int tm_hour; // the number of elapsed hours in the day (0-23)
int tm_mday; / /the number of elapsed days in the month (1-31)
int tm_mon; // the number of elapsed months in the year (0-11)
int tm_year; //the numbers of elapsed years since 1900
int tm_wday; // the number of elapsed days in the week since Sunday (0-6)
int tm_yday; //the number of the elapsed days in the year (0-365)
int tm_isdst; // equals 1 if daylight savings is in effect, zero if not, -1 if unknown
};

You're right, using unitialize pointers can be problematic. But it's not as ominus as you make it sound. The code snippet you refer to is no different than this:

int num = 1;
int * pNum;
pNum = &num;

Used with respect unitialized pointers are not going to blow up or anything.


To refer to certain members of a struct, but not all, you can use the dot or arrow operators. Using the dot operator it goes something like ths:

//using snippet from first post:

cout << tNow.tm_hour << ':' << tNow.tm_min << ':' << tNow.tm_sec << endl;

leave out the colons if you wish. Manipulate tm structs as you need to to use whatever display format you want.