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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 differ (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  require-
       ments described here and the ISO C standard is unintentional. This vol-
       ume 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 structure (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 Defi-
       nitions 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  struc-
       ture  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  struc-
       ture  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), local-
       time()  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 local-
       time()  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, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications 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 Standard, 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)