getdate_r(3) — Linux manual page


GETDATE(3)                Linux Programmer's Manual               GETDATE(3)

NAME         top

       getdate,  getdate_r  - convert a date-plus-time string to broken-down

SYNOPSIS         top

       #include <time.h>

       struct tm *getdate(const char *string);

       extern int getdate_err;

       #include <time.h>

       int getdate_r(const char *string, struct tm *res);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           _XOPEN_SOURCE >= 500

DESCRIPTION         top

       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         top

       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

       On success getdate_r() returns 0; on error it returns one of the
       error numbers shown below.

ERRORS         top

       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

       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         top

              File containing format patterns.

       TZ, LC_TIME
              Variables used by strptime(3).

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface   Attribute     Value                             │
       │getdate()   │ Thread safety │ MT-Unsafe race:getdate env locale │
       │getdate_r() │ Thread safety │ MT-Safe env locale                │

CONFORMING TO         top

       POSIX.1-2001, POSIX.1-2008.

NOTES         top

       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         top

       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      # ISO date (YYYY-MM-DD)
           $ echo '%F' >> $TFILE      # Time (HH:MM:SS)
           $ 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 <time.h>
       #include <stdio.h>
       #include <stdlib.h>

       main(int argc, char *argv[])
           struct tm *tmp;

           for (int j = 1; j < argc; j++) {
               tmp = getdate(argv[j]);

               if (tmp == NULL) {
                   printf("Call %d failed; getdate_err = %d\n",
                          j, getdate_err);

               printf("Call %d (\"%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);


SEE ALSO         top

       time(2), localtime(3), setlocale(3), strftime(3), strptime(3)

COLOPHON         top

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                                 2020-11-01                       GETDATE(3)