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

NAME
       strftime - format date and time

SYNOPSIS
       #include <time.h>

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

DESCRIPTION
       The  strftime()  function  formats the broken-down time tm
       according to the format specification  format  and  places
       the result in the character array s of size max.

       Ordinary characters placed in the format string are copied
       to s without conversion.  Conversion specifiers are intro-
       duced  by  a  `%' character, and are replaced in s as fol-
       lows:

       %a     The abbreviated weekday name according to the  cur-
              rent locale.

       %A     The  full  weekday  name  according  to the current
              locale.

       %b     The abbreviated month name according to the current
              locale.

       %B     The  full  month  name  according  to  the  current
              locale.

       %c     The preferred date and time representation for  the
              current locale.

       %C     The century number (year/100) as a 2-digit integer.
              (SU)

       %d     The day of the month as a decimal number (range  01
              to 31).

       %D     Equivalent  to  %m/%d/%y.  (Yecch  -  for Americans
              only.  Americans should note that  in  other  coun-
              tries %d/%m/%y is rather common. This means that in
              international context this format is ambiguous  and
              should not be used.) (SU)

       %e     Like  %d, the day of the month as a decimal number,
              but a leading zero is replaced by a space. (SU)

       %E     Modifier: use alternative format, see below. (SU)

       %G     The ISO 8601 year with century as a decimal number.
              The 4-digit year corresponding to the ISO week num-
              ber (see %V).  This has the same format  and  value
              as  %y,  except that if the ISO week number belongs
              to the previous or next year,  that  year  is  used
              instead. (TZ)

       %g     Like  %G, but without century, i.e., with a 2-digit
              year (00-99). (TZ)

       %h     Equivalent to %b. (SU)

       %H     The hour as a decimal number using a 24-hour  clock
              (range 00 to 23).

       %I     The  hour as a decimal number using a 12-hour clock
              (range 01 to 12).

       %j     The day of the year as a decimal number (range  001
              to 366).

       %k     The hour (24-hour clock) as a decimal number (range
              0 to 23); single digits are preceded  by  a  blank.
              (See also %H.) (TZ)

       %l     The hour (12-hour clock) as a decimal number (range
              1 to 12); single digits are preceded  by  a  blank.
              (See also %I.) (TZ)

       %m     The month as a decimal number (range 01 to 12).

       %M     The minute as a decimal number (range 00 to 59).

       %n     A newline character. (SU)

       %O     Modifier: use alternative format, see below. (SU)

       %p     Either  `AM'  or  `PM'  according to the given time
              value, or the corresponding strings for the current
              locale.   Noon  is  treated as `pm' and midnight as
              `am'.

       %P     Like %p but in lowercase: `am' or `pm' or a  corre-
              sponding string for the current locale. (GNU)

       %r     The  time  in  a.m. or p.m. notation.  In the POSIX
              locale this is equivalent to `%I:%M:%S %p'. (SU)

       %R     The time in 24-hour notation (%H:%M).  (SU)  For  a
              version including the seconds, see %T below.

       %s     The  number of seconds since the Epoch, i.e., since
              1970-01-01 00:00:00 UTC. (TZ)

       %S     The second as a decimal number (range 00 to 61).

       %t     A tab character. (SU)

       %T     The time in 24-hour notation (%H:%M:%S). (SU)

       %u     The day of the week as a decimal,  range  1  to  7,
              Monday being 1.  See also %w. (SU)

       %U     The  week  number  of the current year as a decimal
              number, range 00 to 53,  starting  with  the  first
              Sunday as the first day of week 01. See also %V and
              %W.

       %V     The ISO 8601:1988 week number of the  current  year
              as  a  decimal number, range 01 to 53, where week 1
              is the first week that has at least 4 days  in  the
              current  year,  and with Monday as the first day of
              the week. See also %U and %W. (SU)

       %w     The day of the week as a decimal,  range  0  to  6,
              Sunday being 0.  See also %u.

       %W     The  week  number  of the current year as a decimal
              number, range 00 to 53,  starting  with  the  first
              Monday as the first day of week 01.

       %x     The  preferred  date representation for the current
              locale without the time.

       %X     The preferred time representation for  the  current
              locale without the date.

       %y     The  year  as  a  decimal  number without a century
              (range 00 to 99).

       %Y     The year as a decimal number including the century.

       %z     The time-zone as hour offset from GMT.  Required to
              emit RFC822-conformant dates (using "%a, %d  %b  %Y
              %H:%M:%S %z"). (GNU)

       %Z     The time zone or name or abbreviation.

       %+     The date and time in date(1) format. (TZ)

       %%     A literal `%' character.

       Some  conversion  specifiers  can be modified by preceding
       them by the E or O modifier to indicate that  an  alterna-
       tive  format should be used.  If the alternative format or
       specification does not exist for the current  locale,  the
       behaviour will be as if the unmodified conversion specifi-
       cation were used. (SU) The Single Unix Specification  men-
       tions  %Ec,  %EC,  %Ex, %EX, %Ry, %EY, %Od, %Oe, %OH, %OI,
       %Om, %OM, %OS, %Ou, %OU, %OV, %Ow,  %OW,  %Oy,  where  the
       effect  of  the  O  modifier is to use alternative numeric
       symbols (say, roman numerals), and that of the E  modifier
       is to use a locale-dependent alternative representation.

       The  broken-down time structure tm is defined in <time.h>.
       See also ctime(3).

RETURN VALUE
       The strftime() function returns the number  of  characters
       placed  in  the array s, not including the terminating NUL
       character, provided the string, including the  terminating
       NUL,  fits.   Otherwise, it returns 0, and the contents of
       the array is undefined.  (Thus at least since libc  4.4.4;
       very  old  versions  of  libc,  such  as libc 4.4.1, would
       return max if the array was too small.)

       Note that the return value 0 does not necessarily indicate
       an  error; for example, in many locales %p yields an empty
       string.

ENVIRONMENT
       The environment variables TZ and LC_TIME are used.

CONFORMING TO
       ANSI C, SVID 3, ISO 9899.   There  are  strict  inclusions
       between the set of conversions given in ANSI C (unmarked),
       those given in the Single Unix Specification (marked  SU),
       those  given  in Olson's timezone package (marked TZ), and
       those given in glibc (marked GNU), except that %+  is  not
       supported  in glibc2. On the other hand glibc2 has several
       more extensions.  POSIX.1 only refers to ANSI  C;  POSIX.2
       describes  under  date(1)  several  extensions  that could
       apply to strftime as well.

SEE ALSO
       date(1), time(2), ctime(3), setlocale(3), sprintf(3)

GNU                       29 March 1999                         1