GETDATE(3)                 POSIX Programmer's Manual                GETDATE(3)



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

NAME
       getdate -- convert user format date and time

SYNOPSIS
       #include <time.h>

       struct tm *getdate(const char *string);

DESCRIPTION
       The getdate() function shall convert a string representation of a date
       or time into a broken-down time.

       The external variable or macro getdate__err, which has type int, is used
       by getdate() to return error values. It is unspecified whether
       getdate__err is a macro or an identifier declared with external linkage,
       and whether or not it is a modifiable lvalue. If a macro definition is
       suppressed in order to access an actual object, or a program defines an
       identifier with the name getdate__err, the behavior is undefined.

       Templates are used to parse and interpret the input string. The
       templates are contained in a text file identified by the environment
       variable DATEMSK.  The DATEMSK variable should be set to indicate the
       full pathname of the file that contains the templates. The first line
       in the template that matches the input specification is used for
       interpretation and conversion into the internal time format.

       The following conversion specifications shall be supported:

       %%      Equivalent to %%.

       %a      Abbreviated weekday name.

       %A      Full weekday name.

       %b      Abbreviated month name.

       %B      Full month name.

       %c      Locale's appropriate date and time representation.

       %C      Century number [00,99]; leading zeros are permitted but not
               required.

       %d      Day of month [01,31]; the leading 0 is optional.

       %D      Date as %%mm/%%dd/%%yy.

       %e      Equivalent to %%dd.

       %h      Abbreviated month name.

       %H      Hour [00,23].

       %I      Hour [01,12].

       %m      Month number [01,12].

       %M      Minute [00,59].

       %n      Equivalent to <newline>.

       %p      Locale's equivalent of either AM or PM.

       %r      The locale's appropriate representation of time in AM and PM
               notation.  In the POSIX locale, this shall be equivalent to
               %%II:%%MM:%%SS %%pp.

       %R      Time as %%HH:%%MM.

       %S      Seconds [00,60]. The range goes to 60 (rather than stopping at
               59) to allow positive leap seconds to be expressed. Since leap
               seconds cannot be predicted by any algorithm, leap second data
               must come from some external source.

       %t      Equivalent to <tab>.

       %T      Time as %%HH:%%MM:%%SS.

       %w      Weekday number (Sunday = [0,6]).

       %x      Locale's appropriate date representation.

       %X      Locale's appropriate time representation.

       %y      Year within century. When a century is not otherwise specified,
               values in the range [69,99] shall refer to years 1969 to 1999
               inclusive, and values in the range [00,68] shall refer to years
               2000 to 2068 inclusive.

               Note:     It is expected that in a future version of this
                         standard the default century inferred from a 2-digit
                         year will change. (This would apply to all commands
                         accepting a 2-digit year as input.)

       %Y      Year as "ccyy" (for example, 2001).

       %Z      Timezone name or no characters if no timezone exists. If the
               timezone supplied by %Z is not the timezone that getdate()
               expects, an invalid input specification error shall result. The
               getdate() function calculates an expected timezone based on
               information supplied to the function (such as the hour, day,
               and month).

       The match between the template and input specification performed by
       getdate() shall be case-insensitive.

       The month and weekday names can consist of any combination of upper and
       lowercase letters. The process can request that the input date or time
       specification be in a specific language by setting the LC__TIME category
       (see setlocale()).

       Leading zeros are not necessary for the descriptors that allow leading
       zeros. However, at most two digits are allowed for those descriptors,
       including leading zeros. Extra white space in either the template file
       or in string shall be ignored.

       The results are undefined if the conversion specifications %%cc, %%xx, and
       %X include unsupported conversion specifications.

       The following rules apply for converting the input specification into
       the internal format:

        *  If %Z is being scanned, then getdate() shall initialize the broken-
           down time to be the current time in the scanned timezone.
           Otherwise, it shall initialize the broken-down time based on the
           current local time as if localtime() had been called.

        *  If only the weekday is given, the day chosen shall be the day,
           starting with today and moving into the future, which first matches
           the named day.

        *  If only the month (and no year) is given, the month chosen shall be
           the month, starting with the current month and moving into the
           future, which first matches the named month. The first day of the
           month shall be assumed if no day is given.

        *  If no hour, minute, and second are given, the current hour, minute,
           and second shall be assumed.

        *  If no date is given, the hour chosen shall be the hour, starting
           with the current hour and moving into the future, which first
           matches the named hour.

       If a conversion specification in the DATEMSK file does not correspond
       to one of the conversion specifications above, the behavior is
       unspecified.

       The getdate() function need not be thread-safe.

RETURN VALUE
       Upon successful completion, getdate() shall return a pointer to a
       struct tm.  Otherwise, it shall return a null pointer and set
       getdate__err to indicate the error.

ERRORS
       The getdate() function shall fail in the following cases, setting
       getdate__err to the value shown in the list below. Any changes to errno
       are unspecified.

        1. The DATEMSK environment variable is null or undefined.

        2. The template file cannot be opened for reading.

        3. Failed to get file status information.

        4. The template file is not a regular file.

        5. An I/O error is encountered while reading the template file.

        6. Memory allocation failed (not enough memory available).

        7. There is no line in the template that matches the input.

        8. Invalid input specification. For example, February 31; or a time is
           specified that cannot be represented in a time_t (representing the
           time in seconds since the Epoch).

       The following sections are informative.

EXAMPLES
        1. The following example shows the possible contents of a template:


               %m
               %A %B %d, %Y, %H:%M:%S
               %A
               %B
               %m/%d/%y %I %p
               %d,%m,%Y %H:%M
               at %A the %dst of %B in %Y
               run job at %I %p,%B %dnd
               %A den %d. %B %Y %H.%M Uhr

        2. The following are examples of valid input specifications for the
           template in Example 1:


               getdate("10/1/87 4 PM");
               getdate("Friday");
               getdate("Friday September 18, 1987, 10:30:30");
               getdate("24,9,1986 10:30");
               getdate("at monday the 1st of december in 1986");
               getdate("run job at 3 PM, december 2nd");

           If the LC__TIME category is set to a German locale that includes
           freitag as a weekday name and oktober as a month name, the
           following would be valid:


               getdate("freitag den 10. oktober 1986 10.30 Uhr");

        3. The following example shows how local date and time specification
           can be defined in the template:

                     +---------------------------+------------------+
                     |        Invocation         | Line in Template |
                     +---------------------------+------------------+
                     |getdate("11/27/86")        | %m/%d/%y         |
                     |getdate("27.11.86")        | %d.%m.%y         |
                     |getdate("86-11-27")        | %y-%m-%d         |
                     |getdate("Friday 12:00:00") | %A %H:%M:%S      |
                     +---------------------------+------------------+
        4. The following examples help to illustrate the above rules assuming
           that the current date is Mon Sep 22 12:19:47 EDT 1986 and the
           LC__TIME category is set to the default C or POSIX locale:

            +-------------+------------------+------------------------------+
            |   Input     | Line in Template |             Date             |
            +-------------+------------------+------------------------------+
            |Mon          | %a               | Mon Sep 22 12:19:47 EDT 1986 |
            |Sun          | %a               | Sun Sep 28 12:19:47 EDT 1986 |
            |Fri          | %a               | Fri Sep 26 12:19:47 EDT 1986 |
            |September    | %B               | Mon Sep 1 12:19:47 EDT 1986  |
            |January      | %B               | Thu Jan 1 12:19:47 EST 1987  |
            |December     | %B               | Mon Dec 1 12:19:47 EST 1986  |
            |Sep Mon      | %b %a            | Mon Sep 1 12:19:47 EDT 1986  |
            |Jan Fri      | %b %a            | Fri Jan 2 12:19:47 EST 1987  |
            |Dec Mon      | %b %a            | Mon Dec 1 12:19:47 EST 1986  |
            |Jan Wed 1989 | %b %a %Y         | Wed Jan 4 12:19:47 EST 1989  |
            |Fri 9        | %a %H            | Fri Sep 26 09:00:00 EDT 1986 |
            |Feb 10:30    | %b %H:%S         | Sun Feb 1 10:00:30 EST 1987  |
            |10:30        | %H:%M            | Tue Sep 23 10:30:00 EDT 1986 |
            |13:30        | %H:%M            | Mon Sep 22 13:30:00 EDT 1986 |
            +-------------+------------------+------------------------------+
APPLICATION USAGE
       Although historical versions of getdate() did not require that <time.h>
       declare the external variable getdate__err, this volume of POSIX.1-2017
       does require it. The standard developers encourage applications to
       remove declarations of getdate__err and instead incorporate the
       declaration by including <time.h>.

       Applications should use %Y (4-digit years) in preference to %y (2-digit
       years).

RATIONALE
       In standard locales, the conversion specifications %%cc, %%xx, and %X do
       not include unsupported conversion specifiers and so the text regarding
       results being undefined is not a problem in that case.

FUTURE DIRECTIONS
       None.

SEE ALSO
       ctime(), localtime(), setlocale(), strftime(), times()

       The Base Definitions volume of POSIX.1-2017, <time.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                           GETDATE(3)
