STRFTIME(3) UNIX Programmer's Manual STRFTIME(3) NAME strftime - generate formatted time information SYNOPSIS #include #include size_t strftime(char *s, size_t maxsize, const char *format, const struct tm *timeptr); DESCRIPTION The following description is transcribed verbatim from the December 7, 1988 draft standard for ANSI C. This draft is essentially identical in technical content to the final ver- sion of the standard. The strftime function places characters into the array pointed to by s as controlled by the string pointed to by format. The format shall be a multibyte character sequence, beginning and ending in its initial shift state. The format string consists of zero or more conversion specifiers and ordinary multibyte characters. A conversion specifier con- sists of a % character followed by a character that deter- mines the behavior of the conversion specifier. All ordi- nary multibyte characters (including the terminating null character) are copied unchanged into the array. If copying takes place between objects that overlap the behavior is undefined. No more than maxsize characters are placed into the array. Each conversion specifier is replaced by appropriate characters as described in the following list. The appropriate characters are determined by the LC_TIME category of the current locale and by the values contained in the structure pointed to by timeptr. %a is replaced by the locale's abbreviated weekday name. %A is replaced by the locale's full weekday name. %b is replaced by the locale's abbreviated month name. %B is replaced by the locale's full month name. %c is replaced by the locale's appropriate date and time representation. %d is replaced by the day of the month as a decimal number (01-31). %H is replaced by the hour (24-hour clock) as a decimal number (00-23). %I is replaced by the hour (12-hour clock) as a decimal number (01-12). %j is replaced by the day of the year as a decimal number (001-366). %m is replaced by the month as a decimal number (01-12). %M is replaced by the minute as a decimal number (00-59). %p is replaced by the locale's equivalent of the AM/PM designations associated with a 12-hour clock. %S is replaced by the second as a decimal number (00-61). %U is replaced by the week number of the year (the first Sunday as the first day of week 1) as a decimal number (00-53). %w is replaced by the weekday as a decimal number [0 (Sunday)-6]. %W is replaced by the week number of the year (the first Monday as the first day of week 1) as a decimal number (00-53). %x is replaced by the locale's appropriate date represen- tation. %X is replaced by the locale's appropriate time represen- tation. %y is replaced by the year without century as a decimal number (00-99). %Y is replaced by the year with century as a decimal number. %Z is replaced by the time zone name or abbreviation, or by no characters if no time zone is determinable. %% is replaced by %. If a conversion specifier is not one of the above, the behavior is undefined. RETURNS If the total number of resulting characters including the terminating null character is not more than maxsize, the strftime function returns the number of characters placed into the array pointed to by s not including the terminating null character. Otherwise, zero is returned and the con- tents of the array are indeterminate. NON-ANSI EXTENSIONS If SYSV_EXT is defined when the routine is compiled, then the following additional conversions will be available. These are borrowed from the System V cftime(3) and ascf- time(3) routines. %D is equivalent to specifying %m/%d/%y. %e is replaced by the day of the month, padded with a blank if it is only one digit. %h is equivalent to %b, above. %n is replaced with a newline character (ASCII LF). %r is equivalent to specifying %I:%M:%S %p. %R is equivalent to specifying %H:%M:. %T is equivalent to specifying %H:%M:%S. %t is replaced with a TAB character. POSIX 1003.2 EXTENSIONS If POSIX2_DATE is defined, then all of the conversions available with SYSV_EXT are available, as well as the fol- lowing additional conversions: %C The century, as a number between 00 and 99. In additon, the alternate representations %Ec, %EC, %Ex, %Ey, %EY, %Od, %Oe, %OH, %OI, %Om, %OM, %OS, %OU, %Ow, %OW, and %Oy are recognized, but their normal representations are used. SEE ALSO time(2), ctime(3), localtime(3) BUGS This version does not handle multibyte characters or pay attention to the setting of the LC_TIME environment vari- able. It is not clear what is ``appropriate'' for the C locale; the values returned are a best guess on the author's part. CAVEATS This implementation calls tzset(3) exactly once. If the TZ environment variable is changed after strftime has been called, then tzset(3) must be called again, explicitly, in order for the correct timezone information to be available. AUTHOR Arnold Robbins AudioFAX, Inc. Suite 200 2000 Powers Ferry Road Marietta, GA. 30067 U.S.A. INTERNET: arnold@audiofax.com UUCP: emory!audfax!arnold Phone: +1 404 618 4281 Fax-box: +1 404 618 4581 ACKNOWLEDGEMENTS Thanks to Geoff Clare for helping debug earlier versions of this routine. Additional thanks to Arthur David Olsen for some code improvements.