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



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

NAME
       ctime, ctime_r - convert a time value to a date and time string

SYNOPSIS
       #include <time.h>

       char *ctime(const time_t *clock);


       char *ctime_r(const time_t *clock, char *buf);


DESCRIPTION
       For  ctime():    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  ctime()  function shall convert the time pointed to by clock, representing time in seconds since the Epoch, to local
       time in the form of a string. It shall be equivalent to:


              asctime(localtime(clock))

       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 char. Execution of any of the functions may overwrite the information returned in
       either of these objects by any of the other functions.

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

       The  ctime_r()  function  shall  convert  the calendar time pointed to by clock to local time in exactly the same form as
       ctime() and put the string into the array pointed to by buf (which shall be at least 26 bytes in size) and return buf.

       Unlike ctime(), the thread-safe version ctime_r() is not required to set tzname.

RETURN VALUE
       The ctime() function shall return the pointer returned by asctime() with that broken-down time as an argument.

       Upon successful completion, ctime_r() shall return a pointer to the string pointed to by buf. When an  error  is  encoun-
       tered, a null pointer shall be returned.

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(). The ctime() function is
       included for compatibility with older implementations, and does not support localized date and  time  formats.   Applica-
       tions should use the strftime() function to achieve maximum portability.

       The  ctime_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
       asctime(), clock(), difftime(), gmtime(), localtime(), mktime(), strftime(), strptime(), time(), utime(), the Base  Defi-
       nitions 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,  Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                     CTIME(3P)