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LOCALTIME(3P)              POSIX Programmer's Manual             LOCALTIME(3P)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (consult the corresponding Linux manual page for details of Linux behavior), or the interface  may  not  be
       implemented on Linux.

NAME
       localtime, localtime_r - convert a time value to a broken-down local time

SYNOPSIS
       #include <time.h>

       struct tm *localtime(const time_t *timer);


       struct tm *localtime_r(const time_t *restrict timer,
              struct tm *restrict result);


DESCRIPTION
       For  localtime():    The functionality described on this reference page is aligned with the ISO C standard. Any
       conflict between the requirements described here and the  ISO C  standard  is  unintentional.  This  volume  of
       IEEE Std 1003.1-2001 defers to the ISO C standard.

       The  localtime()  function shall convert the time in seconds since the Epoch pointed to by timer into a broken-
       down time, expressed as a local time. The function corrects for the timezone and any seasonal time adjustments.
       Local timezone information is used as though localtime() calls tzset().

       The relationship between a time in seconds since the Epoch used as an argument to localtime() and the tm struc-
       ture (defined in the <time.h> header) is that the result shall be as specified in the expression given  in  the
       definition  of  seconds since the Epoch (see the Base Definitions volume of IEEE Std 1003.1-2001, Section 4.14,
       Seconds Since the Epoch) corrected for timezone and any seasonal time  adjustments,  where  the  names  in  the
       structure and in the expression correspond.

       The same relationship shall apply for localtime_r().

       The localtime() function need not be reentrant. A function that is not required to be reentrant is not required
       to be thread-safe.

       The asctime(), ctime(), gmtime(), and localtime() functions shall return values in one of two static objects: a
       broken-down  time  structure  and  an  array  of type char. Execution of any of the functions may overwrite the
       information returned in either of these objects by any of the other functions.

       The localtime_r() function shall convert the time in seconds since the Epoch pointed to by timer into a broken-
       down  time  stored  in  the  structure  to  which result points. The localtime_r() function shall also return a
       pointer to that same structure.

       Unlike localtime(), the reentrant version is not required to set tzname.

RETURN VALUE
       Upon successful completion, the localtime() function shall return a pointer to the broken-down time  structure.
       If an error is detected, localtime() shall return a null pointer  and set errno to indicate the error.

       Upon  successful  completion,  localtime_r() shall return a pointer to the structure pointed to by the argument
       result.

ERRORS
       The localtime() function shall fail if:

       EOVERFLOW
              The result cannot be represented.


       The following sections are informative.

EXAMPLES
   Getting the Local Date and Time
       The following example uses the time() function to calculate the time elapsed, in seconds, since January 1, 1970
       0:00  UTC  (the  Epoch),  localtime() to convert that value to a broken-down time, and asctime() to convert the
       broken-down time values into a printable string.


              #include <stdio.h>
              #include <time.h>


              int main(void)
              {
                  time_t result;


                  result = time(NULL);
                  printf("%s%ju secs since the Epoch\n",
                      asctime(localtime(&result)),
                          (uintmax_t)result);
                  return(0);
              }

       This example writes the current time to stdout in a form like this:


              Wed Jun 26 10:32:15 1996
              835810335 secs since the Epoch

   Getting the Modification Time for a File
       The following example gets the modification time for a file. The localtime() function converts the time_t value
       of  the  last  modification  date, obtained by a previous call to stat(), into a tm structure that contains the
       year, month, day, and so on.


              #include <time.h>
              ...
              struct stat statbuf;
              ...
              tm = localtime(&statbuf.st_mtime);
              ...

   Timing an Event
       The following example gets the current time, converts it to a  string  using  localtime()  and  asctime(),  and
       prints it to standard output using fputs(). It then prints the number of minutes to an event being timed.


              #include <time.h>
              #include <stdio.h>
              ...
              time_t now;
              int minutes_to_event;
              ...
              time(&now);
              printf("The time is ");
              fputs(asctime(localtime(&now)), stdout);
              printf("There are still %d minutes to the event.\n",
                  minutes_to_event);
              ...

APPLICATION USAGE
       The  localtime_r()  function  is  thread-safe  and returns values in a user-supplied buffer instead of possibly
       using a static data area that may be overwritten by each call.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       asctime(), clock(),  ctime(),  difftime(),  getdate(),  gmtime(),  mktime(),  strftime(),  strptime(),  time(),
       utime(), the Base Definitions volume of IEEE Std 1003.1-2001, <time.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  Issue  6,  Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The
       Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Stan-
       dard,  the  original  IEEE  and  The  Open Group Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .



IEEE/The Open Group                  2003                        LOCALTIME(3P)