HELPLIB.HLB  —  CRTL  strftime
    Uses date and time information stored in a tm structure to create
    an output string. The format of the output string is controlled
    by a format string.

    Format

      #include  <time.h>

      size_t strftime  (char *s, size_t maxsize, const char *format,
                       const struct tm *timeptr);

1  –  Function Variants

    Compiling with the _DECC_V4_SOURCE and _VMS_V6_SOURCE feature-
    test macros defined enables a local-time-based entry point to
    the strftime function that is equivalent to the behavior before
    OpenVMS Version 7.0.

2  –  Arguments

 s

    A pointer to the resultant string.

 maxsize

    The maximum number of bytes to be stored in the resultant string,
    including the null terminator.

 format

    A pointer to a string that controls the format of the output
    string.

 timeptr

    A pointer to the local time (tm) structure. The tm structure is
    defined in the <time.h> header file.

3  –  Description

    The strftime function uses data in the structure pointed to
    by timeptr to create the string pointed to by s. A maximum of
    maxsize bytes is copied to s.

    The format string consists of zero or more conversion
    specifications and ordinary characters. All ordinary characters
    (including the terminating null character) are copied unchanged
    into the output string. A conversion specification defines how
    data in the tm structure is formatted in the output string.

    A conversion specification consists of a percent (%) character
    followed by one or more optional characters (see Optional
    Elements of strftime Conversion Specifications), and concluding
    with a conversion specifier (see strftime Conversion Specifiers).
    If any of the optional characters listed in Optional Elements
    of strftime Conversion Specifications are specified, they must
    appear in the order shown in the table.

    The strftime function behaves as if it called tzset.

    Table REF-7 Optional Elements of strftime Conversion
                Specifications

    Element    Meaning

    -          Optional with the field width to specify that the field
               is left-justified and padded with spaces. This cannot
               be used with the 0 element.
    0          Optional with the field width to specify that the field
               is right-justified and padded with zeros. This cannot
               be used with the - element.
    field      A decimal integer that specifies the maximum field
    width      width
    .precision A decimal integer that specifies the precision of data
               in a field.

               For the d, H, I, j, m, M, o, S, U, w, W, y, and Y
               conversion specifiers, the precision specifier is the
               minimum number of digits to appear in the field. If
               the conversion specification has fewer digits than that
               specified by the precision, leading zeros are added.

               For the a, A, b, B, c, D, E, h, n, N, p, r, t, T,
               x, X, Z, and % conversion specifiers, the precision
               specifier is the maximum number of characters to appear
               in the field. If the conversion specification has
               more characters than that specified by the precision,
               characters are truncated on the right.

               The default precision for the d, H, I, m, M, o, S, U,
               w, W, y and Y conversion specifiers is 2; the default
               precision for the j conversion specifier is 3.

    Note that the list of conversion specifications in Optional
    Elements of strftime Conversion Specifications are extensions
    to the XPG4 specification.

    strftime Conversion Specifiers lists the conversion specifiers.
    The strftime function uses fields in the LC_TIME category of
    the program's current locale to provide a value. For example, if
    %B is specified, the function accesses the mon field in LC_TIME
    to find the full month name for the month specified in the tm
    structure. The result of using invalid conversion specifiers is
    undefined.

    Table REF-8 strftime Conversion Specifiers

    Specifier  Replaced by

    a          The locale's abbreviated weekday name
    A          The locale's full weekday name
    b          The locale's abbreviated month name
    B          The locale's full month name
    c          The locale's appropriate date and time representation
    C          The century number (the year divided by 100 and
               truncated to an integer) as a decimal number (00 -
               99)
    d          The day of the month as a decimal number (01 - 31)
    D          Same as %m/%d/%y
    e          The day of the month as a decimal number (1 - 31) in a
               2-digit field with the leading space character fill
    Ec         The locale's alternative date and time representation
    EC         The name of the base year (period) in the locale's
               alternative representation
    Ex         The locale's alternative date representation
    EX         The locale's alternative time representation
    Ey         The offset from the base year (%EC) in the locale's
               alternative representation
    EY         The locale's full alternative year representation
    h          Same as %b
    H          The hour (24-hour clock) as a decimal number (00 - 23)
    I          The hour (12-hour clock) as a decimal number (01 - 12)
    j          The day of the year as a decimal number (001 - 366)
    m          The month as a decimal number (01 - 12)
    M          The minute as a decimal number (00 - 59)
    n          The new-line character
    Od         The day of the month using the locale's alternative
               numeric symbols
    Oe         The date of the month using the locale's alternative
               numeric symbols
    OH         The hour (24-hour clock) using the locale's alternative
               numeric symbols
    OI         The hour (12-hour clock) using the locale's alternative
               numeric symbols
    Om         The month using the locale's alternative numeric
               symbols
    OM         The minutes using the locale's alternative numeric
               symbols
    OS         The seconds using the locale's alternative numeric
               symbols
    Ou         The weekday as a number in the locale's alternative
               representation (Monday=1)
    OU         The week number of the year (Sunday as the first day
               of the week) using the locale's alternative numeric
               symbols
    OV         The week number of the year (Monday as the first day
               of the week) as a decimal number (01 - 53) using the
               locale's alternative numeric symbols. If the week
               containing January 1 has four or more days in the
               new year, it is considered as week 1. Otherwise, it
               is considered as week 53 of the previous year, and the
               next week is week 1.
    Ow         The weekday as a number (Sunday=0) using the locale's
               alternative numeric symbols
    OW         The week number of the year (Monday as the first day
               of the week) using the locale's alternative numeric
               symbols
    Oy         The year without the century using the locale's
               alternative numeric symbols
    p          The locale's equivalent of the AM/PM designations
               associated with a 12-hour clock
    r          The time in AM/PM notation
    R          The time in 24-hour notation (%H:%M)
    S          The second as a decimal number (00 - 61)
    t          The tab character
    T          The time (%H:%M:%S)
    u          The weekday as a decimal number between 1 and 7
               (Monday=1)
    U          The week number of the year (the first Sunday as the
               first day of week 1) as a decimal number (00 - 53)
    V          The week number of the year (Monday as the first day
               of the week) as a decimal number (00 - 53). If the
               week containing January 1 has four or more days in the
               new year, it is considered as week 1. Otherwise, it
               is considered as week 53 of the previous year, and the
               next week is week 1.
    w          The weekday as a decimal number (0 [Sunday] - 6)
    W          The week number of the year (the first Monday as the
               first day of week 1) as a decimal number (00 - 53)
    x          The locale's appropriate date representation
    X          The locale's appropriate time representation
    y          The year without century as a decimal number (00 - 99)
    Y          The year with century as a decimal number
    Z          Time-zone name or abbreviation. If time-zone
               information is not available, no character is output.
    %          Literal % character.

4  –  Return Values

    x                  The number of characters placed into the array
                       pointed to by s, not including the terminating
                       null character.
    0                  Indicates an error occurred. The contents of
                       the array are indeterminate.

5  –  Example

        #include <stdlib.h>
        #include <stdio.h>
        #include <time.h>
        #include <locale.h>
        #include <errno.h>

        #define NUM_OF_DATES  7
        #define BUF_SIZE 256

        /* This program formats a number of different dates, once */
        /* using the C locale and then using the fr_FR.ISO8859-1  */
        /* locale. Date and time formatting is done using strftime(). */

        main()
        {
            int count,
                i;
            char buffer[BUF_SIZE];
            struct tm *tm_ptr;
            time_t time_list[NUM_OF_DATES] =
            {500, 68200000, 694223999, 694224000,
             704900000, 705000000, 705900000};

            /* Display dates using the C locale */
            printf("\nUsing the C locale:\n\n");

            setlocale(LC_ALL, "C");

            for (i = 0; i < NUM_OF_DATES; i++) {
                /* Convert to a tm structure */
                tm_ptr = localtime(&time_list[i]);

                /* Format the date and time */
                count = strftime(buffer, BUF_SIZE,
                       "Date: %A %d %B %Y%nTime: %T%n%n", tm_ptr);
                if (count == 0) {
                    perror("strftime");
                    exit(EXIT_FAILURE);
                }

                /* Print the result */
               printf(buffer);
            }

            /* Display dates using the fr_FR.ISO8859-1 locale */
            printf("\nUsing the fr_FR.ISO8859-1 locale:\n\n");

            setlocale(LC_ALL, "fr_FR.ISO8859-1");

            for (i = 0; i < NUM_OF_DATES; i++) {
                /* Convert to a tm structure */
                tm_ptr = localtime(&time_list[i]);

                /* Format the date and time */
                count = strftime(buffer, BUF_SIZE,
                       "Date: %A %d %B %Y%nTime: %T%n%n", tm_ptr);
                if (count == 0) {
                    perror("strftime");
                    exit(EXIT_FAILURE);
                }

                /* Print the result */
                printf(buffer);
            }
        }

    Running the example program produces the following result:

    Using the C locale:

    Date: Thursday 01 January 1970
    Time: 00:08:20

    Date: Tuesday 29 February 1972
    Time: 08:26:40

    Date: Tuesday 31 December 1991
    Time: 23:59:59

    Date: Wednesday 01 January 1992
    Time: 00:00:00

    Date: Sunday 03 May 1992
    Time: 13:33:20

    Date: Monday 04 May 1992
    Time: 17:20:00

    Date: Friday 15 May 1992
    Time: 03:20:00

    Using the fr_FR.ISO8859-1 locale:

    Date: jeudi 01 janvier 1970
    Time: 00:08:20

    Date: mardi 29 février 1972
    Time: 08:26:40

    Date: mardi 31 décembre 1991
    Time: 23:59:59

    Date: mercredi 01 janvier 1992
    Time: 00:00:00

    Date: dimanche 03 mai 1992
    Time: 13:33:20

    Date: lundi 04 mai 1992
    Time: 17:20:00

    Date: vendredi 15 mai 1992
    Time: 03:20:00
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