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GETDATE(3P) POSIX Programmer's Manual GETDATE(3P)
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.
getdate — convert user format date and time
#include <time.h>
struct tm *getdate(const char *string);
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.
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.
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.
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 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 │
└─────────────┴──────────────────┴──────────────────────────────┘
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 declaration by including <time.h>.
Applications should use %Y (4-digit years) in preference to %y
(2-digit years).
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.
None.
ctime(3p), localtime(3p), setlocale(3p), strftime(3p), times(3p)
The Base Definitions volume of POSIX.1‐2008, time.h(0p)
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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 GETDATE(3P)
Pages that refer to this page: time.h(0p), localtime(3p), strftime(3p)