trusty (3) asctime_r.3posix.gz

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,
       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 .