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ASCTIME(3P)                POSIX Programmer's Manual               ASCTIME(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
       asctime, asctime_r - convert date and time to a string

SYNOPSIS
       #include <time.h>

       char *asctime(const struct tm *timeptr);


       char *asctime_r(const struct tm *restrict tm, char *restrict buf);


DESCRIPTION
       For  asctime():    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  asctime() function shall convert the broken-down time in the structure pointed to by timeptr into a string
       in the form:


              Sun Sep 16 01:03:52 1973\n\0

       using the equivalent of the following algorithm:


              char *asctime(const struct tm *timeptr)
              {
                  static char wday_name[7][3] = {
                      "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
                  };
                  static char mon_name[12][3] = {
                      "Jan", "Feb", "Mar", "Apr", "May", "Jun",
                      "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
                  };
                  static char result[26];


                  sprintf(result, "%.3s %.3s%3d %.2d:%.2d:%.2d %d\n",
                      wday_name[timeptr->tm_wday],
                      mon_name[timeptr->tm_mon],
                      timeptr->tm_mday, timeptr->tm_hour,
                      timeptr->tm_min, timeptr->tm_sec,
                      1900 + timeptr->tm_year);
                  return result;
              }

       The tm structure is defined in the <time.h> header.

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

       The asctime_r() function shall convert the broken-down time in the structure pointed to by tm into a string (of
       the same form as that returned by asctime()) that is placed in the  user-supplied  buffer  pointed  to  by  buf
       (which shall contain at least 26 bytes) and then return buf.

RETURN VALUE
       Upon successful completion, asctime() shall return a pointer to the string.

       Upon  successful  completion,  asctime_r() shall return a pointer to a character string containing the date and
       time. This string is pointed to by the argument buf. If the function is unsuccessful, it shall return NULL.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Values for the broken-down time structure can be obtained by calling gmtime() or localtime(). This function  is
       included  for  compatibility  with older implementations, and does not support localized date and time formats.
       Applications should use strftime() to achieve maximum portability.

       The asctime_r() function is thread-safe and shall return 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
       clock(),  ctime(),  difftime(),  gmtime(),  localtime(), 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                          ASCTIME(3P)