xref: /third_party/tzdata/newstrftime.3.txt

newstrftime(3)             Library Functions Manual             newstrftime(3)

NAME
       strftime - format date and time

SYNOPSIS
       #include <time.h>

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

       cc ... -ltz

DESCRIPTION
       The strftime function formats the information from *timeptr into the
       array pointed to by buf according to the string pointed to by format.

       The format string consists of zero or more conversion specifications
       and ordinary characters.  All ordinary characters are copied directly
       into the array.  A conversion specification consists of a percent sign
       and one other character.

       No more than maxsize bytes are placed into the array.

       Each conversion specification is replaced by the characters as follows
       which are then copied into the array.  The characters depend on the
       values of zero or more members of *timeptr as specified by brackets in
       the description.  If a bracketed member name is followed by "+",
       strftime can use the named member even though POSIX.1-2017 does not
       list it; if the name is followed by "-", strftime ignores the member
       even though POSIX.1-2017 lists it which means portable code should set
       it.  For portability, *timeptr should be initialized as if by a
       successful call to gmtime, localtime, mktime, timegm, or similar
       functions.

       %A     is replaced by the locale's full weekday name.  [tm_wday]

       %a     is replaced by the locale's abbreviated weekday name.  [tm_wday]

       %B     is replaced by the locale's full month name.  [tm_mon]

       %b or %h
              is replaced by the locale's abbreviated month name.  [tm_mon]

       %C     is  replaced by the century (a year divided by 100 and truncated
              to an integer) as a decimal number, with at least two digits  by
              default.  [tm_year]

       %c     is   replaced   by   the  locale's  appropriate  date  and  time
              representation.  [tm_year, tm_yday,  tm_mon,  tm_mday,  tm_wday,
              tm_hour, tm_min, tm_sec, tm_gmtoff+, tm_zone+, tm_isdst-].

       %D     is equivalent to %m/%d/%y.  [tm_year, tm_mon, tm_mday]

       %d     is replaced by the day of the month as a decimal number [01,31].
              [tm_mday]

       %e     is  replaced  by  the  day  of month as a decimal number [1,31];
              single digits are preceded by a blank.  [tm_mday]

       %F     is equivalent to %Y-%m-%d (the ISO 8601 date format).  [tm_year,
              tm_mon, tm_mday]

       %G     is replaced by the ISO 8601  year  with  century  as  a  decimal
              number.   See  also  the %V conversion specification.  [tm_year,
              tm_yday, tm_wday]

       %g     is replaced by the ISO 8601 year without century  as  a  decimal
              number [00,99].  This is the year that includes the greater part
              of the week.  (Monday as the first day of a week).  See also the
              %V conversion specification.  [tm_year, tm_yday, tm_wday]

       %H     is  replaced  by  the  hour  (24-hour clock) as a decimal number
              [00,23].  [tm_hour]

       %I     is replaced by the hour (12-hour  clock)  as  a  decimal  number
              [01,12].  [tm_hour]

       %j     is  replaced  by  the  day  of  the  year  as  a  decimal number
              [001,366].  [tm_yday]

       %k     is replaced by the hour (24-hour  clock)  as  a  decimal  number
              [0,23]; single digits are preceded by a blank.  [tm_hour]

       %l     is  replaced  by  the  hour  (12-hour clock) as a decimal number
              [1,12]; single digits are preceded by a blank.  [tm_hour]

       %M     is replaced by the minute as a decimal number [00,59].  [tm_min]

       %m     is replaced by the month as a decimal number [01,12].  [tm_mon]

       %n     is replaced by a newline.

       %p     is replaced by the locale's equivalent of either "AM"  or  "PM".
              [tm_hour]

       %R     is replaced by the time in the format %H:%M.  [tm_hour, tm_min]

       %r     is replaced by the locale's representation of 12-hour clock time
              using AM/PM notation.  [tm_hour, tm_min, tm_sec]

       %S     is  replaced  by  the  second  as a decimal number [00,60].  The
              range of seconds is [00,60] instead of [00,59] to allow for  the
              periodic occurrence of leap seconds.  [tm_sec]

       %s     is  replaced  by  the  number  of  seconds  since the Epoch (see
              ctime(3)).  Although %s is reliable in this  implementation,  it
              can  have glitches on other platforms (notably platforms lacking
              tm_gmtoff), so  portable  code  should  format  a  time_t  value
              directly  via  something  like  sprintf instead of via localtime
              followed by strftime  with  "%s".   [tm_year,  tm_mon,  tm_mday,
              tm_hour, tm_min, tm_sec, tm_gmtoff+, tm_isdst-].

       %T     is  replaced  by  the  time  in  the format %H:%M:%S.  [tm_hour,
              tm_min, tm_sec]

       %t     is replaced by a tab.

       %U     is replaced by the week number of the year (Sunday as the  first
              day  of  the  week)  as  a  decimal  number  [00,53].  [tm_wday,
              tm_yday, tm_year-]

       %u     is replaced by the weekday (Monday as the first day of the week)
              as a decimal number [1,7].  [tm_wday]

       %V     is replaced by the week number of the year (Monday as the  first
              day  of  the  week)  as  a  decimal number [01,53].  If the week
              containing January 1 has four or more days in the new year, then
              it is week 1; otherwise it is week 53 of the previous year,  and
              the next week is week 1.  The year is given by the %G conversion
              specification.  [tm_year, tm_yday, tm_wday]

       %W     is  replaced by the week number of the year (Monday as the first
              day of  the  week)  as  a  decimal  number  [00,53].   [tm_yday,
              tm_wday]

       %w     is replaced by the weekday (Sunday as the first day of the week)
              as a decimal number [0,6].  [tm_year, tm_yday, tm_wday]

       %X     is  replaced  by  the  locale's appropriate time representation.
              [tm_year-,  tm_yday-,  tm_mon-,  tm_mday-,  tm_wday-,   tm_hour,
              tm_min, tm_sec, tm_gmtoff+, tm_zone+, tm_isdst-].

       %x     is  replaced  by  the  locale's appropriate date representation.
              [tm_year, tm_yday, tm_mon, tm_mday, tm_wday, tm_hour-,  tm_min-,
              tm_sec-, tm_gmtoff-, tm_zone-, tm_isdst-].

       %Y     is  replaced  by  the  year  with  century  as a decimal number.
              [tm_year]

       %y     is replaced by the year without  century  as  a  decimal  number
              [00,99].  [tm_year]

       %Z     is  replaced  by  the  time  zone  abbreviation, or by the empty
              string if this is not determinable.  [tm_zone+, tm_isdst-]

       %z     is replaced by the offset from the Prime Meridian in the  format
              +HHMM  or  -HHMM (ISO 8601) as appropriate, with positive values
              representing locations east of Greenwich, or by the empty string
              if this is not determinable.  The numeric time zone abbreviation
              -0000 is used when the time is Universal Time but local time  is
              indeterminate;  by  convention  this is used for locations while
              uninhabited, and corresponds to a zero offset when the time zone
              abbreviation begins with "-".  [tm_gmtoff+, tm_zone+, tm_isdst-]

       %%     is replaced by a single %.

       %+     is replaced by the locale's date and  time  in  date(1)  format.
              [tm_year,  tm_yday,  tm_mon,  tm_mday, tm_wday, tm_hour, tm_min,
              tm_sec, tm_gmtoff, tm_zone]

       As a side effect, strftime also behaves as if tzset were called.   This
       is  for compatibility with older platforms, as required by POSIX; it is
       not needed for tzset's own use.

RETURN VALUE
       If the conversion is successful, strftime returns the number  of  bytes
       placed  into  the  array,  not  counting  the terminating NUL; errno is
       unchanged if the returned value is zero.  Otherwise, errno  is  set  to
       indicate  the  error,  zero  is  returned,  and  the array contents are
       unspecified.

ERRORS
       This function fails if:

       [ERANGE]
              The total number of resulting bytes, including  the  terminating
              NUL character, is more than maxsize.

       This function may fail if:

       [EOVERFLOW]
              The  format  includes an %s conversion and the number of seconds
              since the Epoch cannot be represented in a time_t.

SEE ALSO
       date(1), getenv(3), newctime(3), newtzset(3), time(2), tzfile(5)

BUGS
       There is no conversion specification for the phase of the moon.

Time Zone Database                                              newstrftime(3)