GETDATE(3P) POSIX Programmer's Manual GETDATE(3P)
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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 get-
date_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 tem-
plates are contained in a text file identified by the environment vari-
able 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 interpreta-
tion 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 stan-
dard 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 %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. Other-
wise, 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 unspeci-
fied.
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 get-
date_err to indicate the error.
ERRORS
The getdate() function shall fail in the following cases, setting get-
date_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 follow-
ing 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 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.1-2008
does require it. The standard developers encourage applications to
remove declarations of getdate_err and instead incorporate the declara-
tion 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.
SEE ALSO
ctime(), localtime(), setlocale(), strftime(), times()
The Base Definitions volume of POSIX.1-2008, <time.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/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.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 GETDATE(3P)
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