getdate(3C)

getdate -- convert user format date and time

Synopsis

   #include <time.h>
   
   struct tm getdate(const char string);
   

   extern int getdate_err;

Description

getdate converts user-definable date and/or time specifications pointed to by string into a tm structure. The structure declaration is in the time.h header file [see also ctime(3C)].

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 some of the same field descriptors as the ones used by the date command. The first line in the template that matches the input specification is used for interpretation and conversion into the internal time format. If successful, the function getdate returns a pointer to a tm structure; otherwise, it returns NULL and sets the global variable getdate_err to indicate the error.

The following field descriptors are supported:

%%: same as %
%a: abbreviated weekday name
%A: full weekday name
%b: abbreviated month name
%B: full month name
%c: locale's appropriate date and time representation
%d: day of month (01-31; the leading 0 is optional)
%e: same as %d
%D: date as %m/%d/%y
%h: abbreviated month name
%H: hour (00-23)
%I: hour (01-12)
%m: month number (01-12)
%M: minute (00-59)
%n: same as \n
%p: locale's equivalent of either AM or PM
%r: time as %I:%M:%S %p
%R: time as %H:%M
%S: seconds (00-59)
%t: same as tab
%T: time as %H:%M:%S
%w: weekday number (0-6; Sunday = 0)
%x: locale's appropriate date representation
%X: locale's appropriate time representation
%y: year within century (for example, 92). When a century is not otherwise specified, values in the range 69-99 refer to the years 1969-1999 inclusive. Values in the range 00-68 refer to the years 2000-2068 inclusive.
%Y: year as ccyy (for example, 1986)
%Z: time zone name or no characters if no time zone exists

The month and weekday names can consist of any combination of upper- and lowercase letters. Any strings the user puts in are case-insensitive. For example, a string Uhr (as shown below) would be treated the same way as a string uhr. The user can request that the input date or time specification be in a specific language by setting the categories LC_TIME and LC_CTYPE of setlocale.

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 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

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

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

The following examples illustrate the above rules. Assume that the current date is Mon Sep 22 12:19:47 EDT 1986 and that the LC_TIME and LANG environment variables are not set.

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

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

Files

/usr/lib/locale/locale/LC_TIME: language-specific printable files
/usr/lib/locale/locale/LC_CTYPE: codeset-specific printable files

Errors

On failure getdate returns NULL and sets the variable getdate_err to indicate the error.

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: malloc 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 or a time is specified that cannot be represented in a time_t (representing the time in seconds since 00:00:00 UTC, January 1, 1970).

References

ctype(3C), environ(5), setlocale(3C)

Notices

A simpler interface, strptime(3C), is also provided that gives more functionality with finer control. Its use is encouraged instead of getdate.

Subsequent calls to getdate alter the contents of getdate_err.

getdate makes explicit use of macros described in ctype(3C) and is thus affected by the LC_CTYPE category of the current locale.

Previous implementations of getdate may return char*.

If the time zone supplied by %Z is not the same as the time zone getdate expects, an invalid input specification error will result. getdate calculates an expected time zone based on information supplied to the interface (such as hour, day, and month).