getdate(3p) — Linux manual page

PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

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

PROLOG         top

       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         top

       getdate — convert user format date and time

SYNOPSIS         top

       #include <time.h>

       struct tm *getdate(const char *string);

DESCRIPTION         top

       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 %m/%d/%y.

       %e      Equivalent to %d.

       %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 %I:%M:%S %p.

       %R      Time as %H:%M.

       %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 %H:%M:%S.

       %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(3p)).

       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 %c,
       %x, 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         top

       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         top

       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         top

        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         top

       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         top

       In standard locales, the conversion specifications %c, %x, 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         top

       None.

SEE ALSO         top

       ctime(3p), localtime(3p), setlocale(3p), strftime(3p), times(3p)

       The Base Definitions volume of POSIX.1‐2017, time.h(0p)

COPYRIGHT         top

       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(3P)

Pages that refer to this page: time.h(0p)localtime(3p)strftime(3p)