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NAME
getdate, getdate_r - convert a date-plus-time string to broken-down time
LIBRARY
Standard C library (libc, -lc)
SYNOPSIS
#include <time.h>
struct tm *getdate(const char *string);
extern int getdate_err;
int getdate_r(const char *restrict string, struct tm *restrict res);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
getdate():
_XOPEN_SOURCE >= 500
getdate_r():
_GNU_SOURCE
DESCRIPTION
The function getdate() converts a string representation of a date and time, contained in
the buffer pointed to by string, into a broken-down time. The broken-down time is stored
in a tm structure, and a pointer to this structure is returned as the function result.
This tm structure is allocated in static storage, and consequently it will be overwritten
by further calls to getdate().
In contrast to strptime(3), (which has a format argument), getdate() uses the formats
found in the file whose full pathname is given in the environment variable DATEMSK. The
first line in the file that matches the given input string is used for the conversion.
The matching is done case insensitively. Superfluous whitespace, either in the pattern or
in the string to be converted, is ignored.
The conversion specifications that a pattern can contain are those given for strptime(3).
One more conversion specification is specified in POSIX.1-2001:
%Z Timezone name. This is not implemented in glibc.
When %Z is given, the structure containing the broken-down time is initialized with values
corresponding to the current time in the given timezone. Otherwise, the structure is
initialized to the broken-down time corresponding to the current local time (as by a call
to localtime(3)).
When only the day of the week is given, the day is taken to be the first such day on or
after today.
When only the month is given (and no year), the month is taken to be the first such month
equal to or after the current month. If no day is given, it is the first day of the
month.
When no hour, minute, and second are given, the current hour, minute, and second are
taken.
If no date is given, but we know the hour, then that hour is taken to be the first such
hour equal to or after the current hour.
getdate_r() is a GNU extension that provides a reentrant version of getdate(). Rather
than using a global variable to report errors and a static buffer to return the broken
down time, it returns errors via the function result value, and returns the resulting
broken-down time in the caller-allocated buffer pointed to by the argument res.
RETURN VALUE
When successful, getdate() returns a pointer to a struct tm. Otherwise, it returns NULL
and sets the global variable getdate_err to one of the error numbers shown below. Changes
to errno are unspecified.
On success getdate_r() returns 0; on error it returns one of the error numbers shown
below.
ERRORS
The following errors are returned via getdate_err (for getdate()) or as the function
result (for getdate_r()):
1 The DATEMSK environment variable is not defined, or its value is an empty string.
2 The template file specified by DATEMSK cannot be opened for reading.
3 Failed to get file status information.
4 The template file is not a regular file.
5 An error was encountered while reading the template file.
6 Memory allocation failed (not enough memory available).
7 There is no line in the file that matches the input.
8 Invalid input specification.
ENVIRONMENT
DATEMSK
File containing format patterns.
TZ, LC_TIME
Variables used by strptime(3).
ATTRIBUTES
For an explanation of the terms used in this section, see attributes(7).
┌────────────┬───────────────┬────────────────────────────────────────────────────────────┐
│Interface │ Attribute │ Value │
├────────────┼───────────────┼────────────────────────────────────────────────────────────┤
│getdate() │ Thread safety │ MT-Unsafe race:getdate env locale │
├────────────┼───────────────┼────────────────────────────────────────────────────────────┤
│getdate_r() │ Thread safety │ MT-Safe env locale │
└────────────┴───────────────┴────────────────────────────────────────────────────────────┘
STANDARDS
POSIX.1-2001, POSIX.1-2008.
NOTES
The POSIX.1 specification for strptime(3) contains conversion specifications using the %E
or %O modifier, while such specifications are not given for getdate(). In glibc,
getdate() is implemented using strptime(3), so that precisely the same conversions are
supported by both.
EXAMPLES
The program below calls getdate() for each of its command-line arguments, and for each
call displays the values in the fields of the returned tm structure. The following shell
session demonstrates the operation of the program:
$ TFILE=$PWD/tfile
$ echo '%A' > $TFILE # Full name of the day of the week
$ echo '%T' >> $TFILE # Time (HH:MM:SS)
$ echo '%F' >> $TFILE # ISO date (YYYY-MM-DD)
$ date
$ export DATEMSK=$TFILE
$ ./a.out Tuesday '2009-12-28' '12:22:33'
Sun Sep 7 06:03:36 CEST 2008
Call 1 ("Tuesday") succeeded:
tm_sec = 36
tm_min = 3
tm_hour = 6
tm_mday = 9
tm_mon = 8
tm_year = 108
tm_wday = 2
tm_yday = 252
tm_isdst = 1
Call 2 ("2009-12-28") succeeded:
tm_sec = 36
tm_min = 3
tm_hour = 6
tm_mday = 28
tm_mon = 11
tm_year = 109
tm_wday = 1
tm_yday = 361
tm_isdst = 0
Call 3 ("12:22:33") succeeded:
tm_sec = 33
tm_min = 22
tm_hour = 12
tm_mday = 7
tm_mon = 8
tm_year = 108
tm_wday = 0
tm_yday = 250
tm_isdst = 1
Program source
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int
main(int argc, char *argv[])
{
struct tm *tmp;
for (size_t j = 1; j < argc; j++) {
tmp = getdate(argv[j]);
if (tmp == NULL) {
printf("Call %zu failed; getdate_err = %d\n",
j, getdate_err);
continue;
}
printf("Call %zu (\"%s\") succeeded:\n", j, argv[j]);
printf(" tm_sec = %d\n", tmp->tm_sec);
printf(" tm_min = %d\n", tmp->tm_min);
printf(" tm_hour = %d\n", tmp->tm_hour);
printf(" tm_mday = %d\n", tmp->tm_mday);
printf(" tm_mon = %d\n", tmp->tm_mon);
printf(" tm_year = %d\n", tmp->tm_year);
printf(" tm_wday = %d\n", tmp->tm_wday);
printf(" tm_yday = %d\n", tmp->tm_yday);
printf(" tm_isdst = %d\n", tmp->tm_isdst);
}
exit(EXIT_SUCCESS);
}
SEE ALSO
time(2), localtime(3), setlocale(3), strftime(3), strptime(3)