getdate - convert user format date and time
#include <time.h> struct tm *getdate(const char *string);
The getdate() function converts a string representation of a date or time into a broken-down time.
The external variable or macro getdate_err is used by getdate() to return error values.
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 field descriptors are supported:
- same as %
- abbreviated weekday name
- full weekday name
- abbreviated month name
- full month name
- locale's appropriate date and time representation
- century number (00-99; leading zeros are permitted but not required)
- day of month (01-31; the leading 0 is optional)
- date as %m/%d/%y
- same as %d
- abbreviated month name
- hour (00-23)
- hour (01-12)
- month number (01-12)
- minute (00-59)
- same as new line
- locale's equivalent of either AM or PM
- The locale's appropriate representation of time in AM and PM notation. In the POSIX locale, this is equivalent to %I:%M:%S %p
- time as %H:%M
- seconds (00-61). Leap seconds are allowed but are not predictable through use of algorithms.
- same as tab
- time as %H:%M:%S
- weekday number (Sunday = 0 - 6)
- locale's appropriate date representation
- locale's appropriate time representation
- 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).
- year as ccyy (for example, 1994)
- time zone name or no characters if no time zone exists. If the time zone supplied by %Z is not the time zone that getdate() expects, an invalid input specification error will result. The getdate() function calculates an expected time zone 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() is case insensitive.
The month and weekday names can consist of any combination of upper and lower case 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 0's are not necessary for the descriptors that allow leading 0's. However, at most two digits are allowed for those descriptors, including leading 0's. Extra whitespace in either the template file or in string is ignored.
The field descriptors %c, %x, and %X will not be supported if they include unsupported field descriptors.
The following rules apply for converting the input specification into the internal format:
- If %Z is being scanned, then getdate() initialises the broken-down time to be the current time in the scanned time zone. Otherwise it initialises the broken-down time based on the current local time as if localtime() had been called.
- 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.
If a field descriptor specification in the DATEMSK file does not correspond to one of the field descriptors above, the behaviour is unspecified.
This interface need not be reentrant.
Upon successful completion, getdate() returns a pointer to a struct tm. Otherwise, it returns a null pointer and getdate_err is set to indicate the error.
The getdate() function will fail in the following cases, setting getdate_err to the value shown in the list below. Any changes to errno are unspecified.
- The DATEMSK environment variable is null or undefined.
- The template file cannot be opened for reading.
- Failed to get file status information.
- The template file is not a regular file.
- An I/O error is encountered while reading the template file.
- Memory allocation failed (not enough memory available).
- There is no line in the template that matches the input.
- Invalid input specification. For example, February 31; or a time is specified that can not be represented in a time_t (representing the time in seconds since 00:00:00 UTC, January 1, 1970).
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 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");
The following examples 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
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 specification does require it. The Open Group encourages 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).
ctime(), localtime(), setlocale(), strftime(), times(), <time.h>.