Tribblix: manual page: getdate.3c

GETDATE(3C) Standard C Library Functions GETDATE(3C)

NAME

getdate - convert user format date and time

SYNOPSIS

#include <time.h>

struct tm *getdate(const char *string);
extern int getdate_err;

DESCRIPTION

The getdate() function converts user-definable date and/or time
specifications pointed to by string to a tm structure. The tm
structure is defined in the <time.h> header.

User-supplied templates are used to parse and interpret the input
string. The templates are text files created by the user and
identified via the environment variable DATEMSK. Each line in the
template represents an acceptable date and/or time specification
using conversion specifications similar to those used by
strftime(3C) and strptime(3C). Dates before 1902 and after 2037 are
illegal. The first line in the template that matches the input
specification is used for interpretation and conversion into the
internal time format.

Conversion Specifications

The following conversion specifications are supported:

%%
Same as %.

%a
Locale's abbreviated weekday name.

%A
Locale's full weekday name.

%b
Locale's abbreviated month name.

%B
Locale's full month name.

%c
Locale's appropriate date and time representation.

%C
Century number (the year divided by 100 and truncated to an
integer as a decimal number [1,99]); single digits are preceded
by 0; see standards(7). If used without the %y specifier, this
format specifier will assume the current year offset in
whichever century is specified. The only valid years are
between 1902-2037.

%d
day of month [01,31]; leading zero is permitted but not
required.

%D
Date as %m/%d/%y.

%e
Same as %d.

%h
Locale's abbreviated month name.

%H
Hour (24-hour clock) [0,23]; leading zero is permitted but not
required.

%I
Hour (12-hour clock) [1,12]; leading zero is permitted but not
required.

%j
Day number of the year [1,366]; leading zeros are permitted but
not required.

%m
Month number [1,12]; leading zero is permitted but not
required.

%M
Minute [0,59]; leading zero is permitted but not required.

%n
Any white space.

%p
Locale's equivalent of either a.m. or p.m.

%r
Appropriate time representation in the 12-hour clock format
with %p.

%R
Time as %H:%M.

SUSv3
%S
Seconds [0,60]; leading zero is permitted but not required. The
range of values is [00,60] rather than [00,59] to allow for the
occasional leap second.

Default and other standards

%S
Seconds [0,61]; leading zero is permitted but not required. The
range of values is [00,61] rather than [00,59] to allow for the
occasional leap second and even more occasional double leap
second.

%t
Any white space.

%T
Time as %H:%M:%S.

%U
Week number of the year as a decimal number [0,53], with Sunday
as the first day of the week; leading zero is permitted but not
required.

%w
Weekday as a decimal number [0,6], with 0 representing Sunday.

%W
Week number of the year as a decimal number [0,53], with Monday
as the first day of the week; leading zero is permitted but not
required.

%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 refer to years in the twentieth
century (1969 to 1999 inclusive); values in the range 00-68
refer to years in the twenty-first century (2000 to 2068
inclusive).

%Y
Year, including the century (for example, 1993).

%Z
Time zone name or no characters if no time zone exists.

Modified Conversion Specifications

Some conversion specifications can be modified by the E and O
modifier characters to indicate that an alternative format or
specification should be used rather than the one normally used by the
unmodified specification. If the alternative format or specification
does not exist in the current locale, the behavior be as if the
unmodified conversion specification were used.

%Ec
Locale's alternative appropriate date and time representation.

%EC
Name of the base year (period) in the locale's alternative
representation.

%Ex
Locale's alternative date representation.

%EX
Locale's alternative time representation.

%Ey
Offset from %EC (year only) in the locale's alternative
representation.

%EY
Full alternative year representation.

%Od
Day of the month using the locale's alternative numeric
symbols; leading zeros are permitted but not required.

%Oe
Same as %Od.

%OH
Hour (24-hour clock) using the locale's alternative numeric
symbols.

%OI
Hour (12-hour clock) using the locale's alternative numeric
symbols.

%Om
Month using the locale's alternative numeric symbols.

%OM
Minutes using the locale's alternative numeric symbols.

%OS
Seconds using the locale's alternative numeric symbols.

%OU
Week number of the year (Sunday as the first day of the week)
using the locale's alternative numeric symbols.

%Ow
Number of the weekday (Sunday=0) using the locale's
alternative numeric symbols.

%OW
Week number of the year (Monday as the first day of the week)
using the locale's alternative numeric symbols.

%Oy
Year (offset from %C) in the locale's alternative
representation and using the locale's alternative numeric
symbols.

Internal Format Conversion

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

o If only the weekday is given, today is assumed if the
given day is equal to the current day and next week if it
is less.

o If only the month is given, the current month is assumed
if the given month is equal to the current month and next
year if it is less and no year is given. (The first day
of month is assumed if no day is given.)

o If only the year is given, the values of the tm_mon,
tm_mday, tm_yday, tm_wday, and tm_isdst members of the
returned tm structure are not specified.

o If the century is given, but the year within the century
is not given, the current year within the century is
assumed.

o If no hour, minute, and second are given, the current
hour, minute, and second are assumed.

o If no date is given, today is assumed if the given hour is
greater than the current hour and tomorrow is assumed if
it is less.

General Specifications

A conversion specification that is an ordinary character is executed
by scanning the next character from the buffer. If the character
scanned from the buffer differs from the one comprising the
conversion specification, the specification fails, and the differing
and subsequent characters remain unscanned.

A series of conversion specifications composed of %n, %t, white space
characters, or any combination is executed by scanning up to the
first character that is not white space (which remains unscanned), or
until no more characters can be scanned.

Any other conversion specification is executed by scanning characters
until a character matching the next conversion specification is
scanned, or until no more characters can be scanned. These
characters, except the one matching the next conversion
specification, are then compared to the locale values associated with
the conversion specifier. If a match is found, values for the
appropriate tm structure members are set to values corresponding to
the locale information. If no match is found, getdate() fails and no
more characters are scanned.

The month names, weekday names, era names, and alternative numeric
symbols can consist of any combination of upper and lower case
letters. The user can request that the input date or time
specification be in a specific language by setting the LC_TIME
category using setlocale(3C).

RETURN VALUES

If successful, getdate() returns a pointer to a tm structure;
otherwise, it returns NULL and sets the global variable getdate_err
to indicate the error. Subsequent calls to getdate() alter the
contents of getdate_err.

The following is a complete list of the getdate_err settings and
their meanings:

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 error is encountered while reading the template file.

6
The malloc() function failed (not enough memory is available).

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

8
The input specification is invalid (for example, February 31).

USAGE

The getdate() function makes explicit use of macros described on the
ctype(3C) manual page.

EXAMPLES

Example 1: Examples of the getdate() function.

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

The following are examples of valid input specifications for the
above template:

getdate("10/1/87 4 PM")
getdate("Friday")
getdate("Friday September 19 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 LANG environment variable is set to de (German), the
following is valid:

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

Local time and date specification are also supported. The following
examples show 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 |
+---------------------------+------------------+

The following examples illustrate the Internal Format Conversion
rules. Assume that the current date is Mon Sep 22 12:19:47 EDT 1986
and the LANG environment variable is not set.

+-------------+----------------+------------------------------+
|Input | Template Line | Date |
+-------------+----------------+------------------------------+
|Mon | %a | Mon Sep 22 12:19:48 EDT 1986 |
|Sun | %a | Sun Sep 28 12:19:49 EDT 1986 |
|Fri | %a | Fri Sep 26 12:19:49 EDT 1986 |
|September | %B | Mon Sep 1 12:19:49 EDT 1986 |
|January | %B | Thu Jan 1 12:19:49 EST 1987 |
|December | %B | Mon Dec 1 12:19:49 EDT 1986 |
|Sep Mon | %b %a | Mon Sep 1 12:19:50 EDT 1986 |
|Jan Fri | %b %a | Fri Jan 2 12:19:50 EST 1987 |
|Dec Mon | %b %a | Mon Dec 1 12:19:50 EST 1986 |
|Jan Wed 1989 | %b %a %Y | Wed Jan 4 12:19:51 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 |
+-------------+----------------+------------------------------+

ATTRIBUTES