Linux programming file and I/O (7): Time Function Summary

Obtain time from system clock

Time Function introduction:

 

Time. hIs the date and time header file in C/C ++.

Sample Code

# Include <stdio. h>

# Include <time. h>

Int main (void)

{

Time_t timer = time (NULL );

Printf ("ctime is % s \ n", ctime (& timer); // obtain the calendar time

Return 0;

}

Obtain time from system clock

Time_tTime(Time_t *Timer)

Obtain the number of seconds from the standard time point (generally midnight on January 1, January 1, 1970) to the current time.

Clock_tClock(Void)

Obtain the total number of milliseconds from the start of the program to the function call.

Time Function Introduction 1. Function Name: localtime

Function prototype: struct tm * localtime (const time_t * timer)

Function: returns the machine time information expressed in the tm structure.

Function return: The time expressed in the tm structure. The tm structure is defined as follows:

Struct tm {

Int tm_sec;

Int tm_min;

Int tm_hour;

Int tm_mday;

Int tm_mon;

Int tm_year;

Int tm_wday;

Int tm_yday;

Int tm_isdst;

};

Parameter description: timer-machine time obtained using the time () function

File: <time. h>

# Include <time. h>

# Include <stdio. h>

# Include <dos. h>

Int main ()

{

Time_t timer;

Struct tm * tblock;

Timer = time (NULL );

Tblock = localtime (& timer );

Printf ("Local time is: % s", asctime (tblock ));

Return 0;

}

2. Function Name: asctime

Function prototype: char * asctime (struct tm * ptr)

Function: Get the machine time (date and time are converted to ASCII code)

Function return: The returned time string is in the format of week, month, day, hour: minute: Second, year

Parameter description: The structure pointer ptr should be obtained through the localtime () and gmtime () functions.

3. Function Name: ctime

Function prototype: char * ctime (long time)

Function: Get the calendar time.

Function return: Return string format: week, month, day, hour: minute: Second, year

Parameter description: time-this parameter should be obtained by the function time.

File: <time. h>

# Include <stdio. h>

# Include <time. h>

Int main ()

{

Time_t t;

Time (& t );

Printf ("Today's date and time: % s", ctime (& t ));

Return 0;

}

4. Function Name: difftime

Function prototype: double difftime (time_t time2, time_t time1)

Function: returns the time difference between two machines, in seconds.

Function return: time difference, in seconds

Parameter description: time1-machine time 1, time2-machine time 2. This parameter should be obtained using the time function.

File: <time. h>

# Include <time. h>

# Include <stdio. h>

# Include <dos. h>

# Include <conio. h>

Int main ()

{

Time_t first, second;

Clrscr ();

First = time (NULL );

Delay (2000 );

Second = time (NULL );

Printf ("The difference is: % fseconds", difftime (second, first ));

Getch ();

Return 0;

}

5. Function Name: gmtime

Function prototype: struct tm * gmtime (time_t * time)

Function: Obtain the time information in the format of the structured tm.

Function return: Time Information pointer expressed in the structure tm

Parameter description: time-time information obtained using the time () function

File: <time. h>

# Include <stdio. h>

# Include <stdlib. h>

# Include <time. h>

# Include <dos. h>

Char * tzstr = "TZ = PST8PDT ";

Int main ()

{

Time_t t;

Struct tm * gmt, * area;

Putenv (tzstr );

Tzset ();

T = time (NULL );

Area = localtime (& t );

Printf ("Local time is: % s", asctime (area ));

Gmt = gmtime (& t );

Printf ("GMT is: % s", asctime (gmt ));

Return 0;

}

6. Function Name: time

Function prototype: time_t time (time_t * timer)

Function: Get the calendar time of the machine or set the calendar time.

Function return: Machine calendar time

Parameter description: When timer = NULL, the calendar time of the machine is obtained. When timer = time value, it is used to set the calendar time. time_t is a long type.

File: <time. h>

# Include <time. h>

# Include <stdio. h>

# Include <dos. h>

Int main ()

{

Time_t t;

T = time ();

Printf ("The number of seconds since January 1,1970 is % ld", t );

Return 0;

}

7. Function Name: tzset

Function prototype: void tzset (void)

Function: a unix-compatible function used to obtain the time zone. It is useless in a DOS environment.

Function return:

Parameter description:

File: <time. h>

# Include <time. h>

# Include <stdlib. h>

# Include <stdio. h>

Int main ()

{

Time_t td;

Putenv ("TZ = PST8PDT ");

Tzset ();

Time (& td );

Printf ("Current time = % s", asctime (localtime (& td )));

Return 0;

}