# getdate

## PROLOG



           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



           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 **%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



           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 **%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



           None.
    


* * *