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#include <sys/types.h>
#include <time.h>
static char *sweekdays[]={"Sun","Mon","Tue","Wed","Thu","Fri","Sat"};
static char *weekdays[]={"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};
static char *smonths[]={"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
static char *months[]={"January","February","March","April","May","June","July","August","September","October","November","December"};
static char *ampm[]={"am","pm","AM","PM"};
static int i2a(char* dest,unsigned int x) {
register unsigned int tmp=x;
register int len=0;
*dest++=tmp/10+'0'; tmp=tmp%10; ++len;
*dest++=tmp+'0';
return 2;
}
static int i2as(char* dest,unsigned int x) {
int len=i2a(dest,x);
if (*dest=='0') *dest=' ';
return len;
}
size_t strftime(char *s, size_t max, const char *format, const struct tm *tm) {
char *t=s;
const char *src;
char buf[5];
while (*format) {
switch (*format) {
case 0: break;
case '%':
switch (*++format) {
case '%': *t='%'; ++t; break;
case 'a': src=sweekdays[tm->tm_wday]; goto append;
case 'A': src=weekdays[tm->tm_wday]; goto append;
case 'h':
case 'b': src=smonths[tm->tm_mon]; goto append;
case 'B': src=months[tm->tm_mon]; goto append;
case 'c': t+=strftime(t,max-(t-s),"%b %a %d %k:%M:%S %Z %Y",tm); break;
case 'C': buf[i2a(buf,(tm->tm_year+1900)/100)]=0; src=buf; goto append;
case 'd': buf[i2a(buf,tm->tm_mday)]=0; src=buf; goto append;
case 'e': buf[i2as(buf,tm->tm_mday)]=0; src=buf; goto append;
case 'H': buf[i2a(buf,tm->tm_hour)]=0; src=buf; goto append;
case 'I': buf[i2a(buf,tm->tm_hour%12)]=0; src=buf; goto append;
case 'j': buf[i2a(buf,tm->tm_yday)]=0; src=buf; goto append;
case 'k': buf[i2as(buf,tm->tm_hour)]=0; src=buf; goto append;
case 'l': buf[i2as(buf,tm->tm_hour%12)]=0; src=buf; goto append;
case 'm': buf[i2a(buf,tm->tm_mon+1)]=0; src=buf; goto append;
case 'M': buf[i2a(buf,tm->tm_min)]=0; src=buf; goto append;
case 'n': *t='\n'; break;
case 'p': src=ampm[tm->tm_hour>11?3:2]; goto append;
case 'P': src=ampm[tm->tm_hour>11?1:0]; goto append;
case 'r': t+=strftime(t,max-(t-s),"%I:%M:%S %p",tm); break;
case 'R': t+=strftime(t,max-(t-s),"%H:%M",tm); break;
case 'S': buf[i2a(buf,tm->tm_sec)]=0; src=buf; goto append;
case 't': *t='\t'; break;
case 'T': t+=strftime(t,max-(t-s),"%H:%M:%S",tm); break;
case 'u': buf[i2a(buf,tm->tm_wday?tm->tm_wday:7)]=0; src=buf; goto append;
case 'w': buf[i2a(buf,tm->tm_wday)]=0; src=buf; goto append;
case 'x': t+=strftime(t,max-(t-s),"%b %a %d",tm); break;
case 'X': t+=strftime(t,max-(t-s),"%k:%M:%S",tm); break;
case 'y': buf[i2a(buf,tm->tm_year%100)]=0; src=buf; goto append;
case 'Y': i2a(buf,(tm->tm_year+1900)/100); buf[i2a(buf+2,(tm->tm_year%100))+2]=0; src=buf; goto append;
case 'Z': src="GMT"; goto append; /* hehe */
append:
while (*src && t<s+max) { *t=*src; ++t; ++src; }
};
break;
default:
*t=*format; ++t;
}
++format;
if (t>=s+max) break;
continue;
}
*t=0; return t-s;
}
/*
%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
GNU 29 March 1999 3
STRFTIME(3) Linux Programmer's Manual STRFTIME(3)
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)
*/
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