GETDATE(3)

GETDATE(3) | Library Functions Manual | GETDATE(3)

# NAME

getdate, getdate_err — convert user format date and time

# LIBRARY

Standard C Library (libc, -lc)

# SYNOPSIS

#include <time.h>
struct tm *
getdate(const char *str);
extern int getdate_err;

# DESCRIPTION

The getdate() function converts a date or time character string pointed to by str into a static tm structure described in tm(3).
The input string is parsed and interpreted using templates. A text file containing templates is specified by the environment variable `DATEMSK`. This should contain the full path to the template file. Lines in the template file represent acceptable date and/or time conversion specifications. These specifications are similar to those given for strptime(3). The first line in the template file that matches the input string is used to interpret and convert to internal time format.

## Internal Format Conversion

The following rules apply to converting the input into the internal format.

- If only the weekday is given, the conversion assumes today when the weekday matches today or the first future matching weekday.
- If only the month and no year is given, the conversion assumes the current month when the month matches or the first future matching month. The first day of the month is assumed if no day is given.
- If only the year is given, the values of the tm_mon, tm_mday, tm_wday, tm_yday, and tm_isdst members of the returned struct tm are unspecified.
- If the century is given, but the year within the century is not given, the conversion assumes the current year.
- If no hour, minute, and second are given, the conversion assumes the current hour, minute, and second.
- If no date is given, the conversion assumes today when the given hour is greater than the current hour and tomorrow when the given hour is less.
- If %Z is being scanned, then the broken-down time is based on the the current time of the matched timezone and not the current runtime environment timezone.

# RETURN VALUES

If successful, the getdate() function returns a pointer to a static tm structure containing the broken-down time. Otherwise, a null pointer is returned and getdate_err is set to indicate the error.
The variable getdate_err can have the following values:

1
  `DATEMSK` environment variable is null or undefined.
2
  Cannot open the template file for reading.
3
  Get file status failed for template file.
4
  Template file is not a regular file.
5
  Encountered an error while reading the template file.
6
  Cannot allocate memory.
7
  Input string does not match any line in the template file.
8
  Input string is invalid (for example, February 31) or could not be represented in a time_t.

# ENVIRONMENT

`DATEMSK`
  The full path to the text file containing the templates for acceptable date and/or time conversions.

# FILES

/usr/share/examples/getdate/datemsk.template
  An example template file that could be specified via the `DATEMSK` environment variable.

# EXAMPLES

The following example shows the possible contents of a template file:

    %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 for the above template:

    10/1/87 4 PM
    Friday
    Friday September 18, 1987, 10:30:30
    24,9,1986 10:30
    at monday the 1st of december in 1986
    run job at 3 PM, december 2nd

The following examples show how local data and time specification can be defined in the template.

Input String | Line in Template
`11/27/86` | `%m/%d/%y`
`27.11.86` | `%d.%m.%y`
`86-11-27` | `%y-%m-%d`
`Friday 12:00:00` | `%A %H:%M:%S`

The following examples illustrate the Internal Format Conversion rules given that the current date is `Mon Sep 22 12:19:47 EDT 1986` and the `LC_TIME` environment variable is set to the default C locale.

Input String | 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` | `Tue Sep 22 13:30:00 EDT 1986`

# SEE ALSO

ctime(3), localtime(3), mktime(3), strftime(3), strptime(3), time(3)

# STANDARDS

The getdate() function conforms to IEEE Std 1003.1-2001 (“POSIX.1”).

# HISTORY

The getdate function appeared in AT&T System V Release 4 UNIX.

# BUGS

The getdate interface is inherently unsafe for multi-threaded programs or libraries, since it returns a pointer to a static variable and uses a global state variable.

December 14, 2012 | NetBSD 8.3