Originální popis anglicky:
strptime - convert a string representation of time to a time tm structure
Návod, kniha: Linux Programmer's Manual
#define _XOPEN_SOURCE /* glibc2 needs this */
#include <time.h>
char *strptime(const char *s, const char
*format, struct tm *tm);
The
strptime() function is the converse function to
strftime() and
converts the character string pointed to by
s to values which are
stored in the
tm structure pointed to by
tm, using the format
specified by
format. Here
format is a character string that
consists of field descriptors and text characters, reminiscent of
scanf(3). Each field descriptor consists of a
% character
followed by another character that specifies the replacement for the field
descriptor. All other characters in the
format string must have a
matching character in the input string, except for whitespace, which matches
zero or more whitespace characters in the input string. There should be
whitespace or other alphanumeric characters between any two field descriptors.
The
strptime() function processes the input string from left to right.
Each of the three possible input elements (whitespace, literal, or format) are
handled one after the other. If the input cannot be matched to the format
string the function stops. The remainder of the format and input strings are
not processed.
The supported input field descriptors are listed below. In case a text string
(such as a weekday or month name) is to be matched, the comparison is case
insensitive. In case a number is to be matched, leading zeros are permitted
but not required.
- %%
- The % character.
- %a or %A
- The weekday name according to the current locale, in
abbreviated form or the full name.
- %b or %B or %h
- The month name according to the current locale, in
abbreviated form or the full name.
- %c
- The date and time representation for the current
locale.
- %C
- The century number (0-99).
- %d or %e
- The day of month (1-31).
- %D
- Equivalent to %m/%d/%y. (This is the American style date,
very confusing to non-Americans, especially since %d/%m/%y is widely used
in Europe. The ISO 8601 standard format is %Y-%m-%d.)
- %H
- The hour (0-23).
- %I
- The hour on a 12-hour clock (1-12).
- %j
- The day number in the year (1-366).
- %m
- The month number (1-12).
- %M
- The minute (0-59).
- %n
- Arbitrary whitespace.
- %p
- The locale's equivalent of AM or PM. (Note: there may be
none.)
- %r
- The 12-hour clock time (using the locale's AM or PM). In
the POSIX locale equivalent to %I:%M:%S %p. If t_fmt_ampm is empty
in the LC_TIME part of the current locale then the behaviour is
undefined.
- %R
- Equivalent to %H:%M.
- %S
- The second (0-60; 60 may occur for leap seconds; earlier
also 61 was allowed).
- %t
- Arbitrary whitespace.
- %T
- Equivalent to %H:%M:%S.
- %U
- The week number with Sunday the first day of the week
(0-53). The first Sunday of January is the first day of week 1.
- %w
- The weekday number (0-6) with Sunday = 0.
- %W
- The week number with Monday the first day of the week
(0-53). The first Monday of January is the first day of week 1.
- %x
- The date, using the locale's date format.
- %X
- The time, using the locale's time format.
- %y
- The year within century (0-99). When a century is not
otherwise specified, values in the range 69-99 refer to years in the
twentieth century (1969-1999); values in the range 00-68 refer to years in
the twenty-first century (2000-2068).
- %Y
- The year, including century (for example, 1991).
Some field descriptors can be modified by the E or O modifier characters to
indicate that an alternative format or specification should be used. If the
alternative format or specification does not exist in the current locale, the
unmodified field descriptor is used.
The E modifier specifies that the input string may contain alternative
locale-dependent versions of the date and time representation:
- %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 %EC (year only) in the locale's alternative
representation.
- %EY
- The full alternative year representation.
The O modifier specifies that the numerical input may be in an alternative
locale-dependent format:
- %Od or %Oe
- The day of the month using the locale's alternative numeric
symbols; leading zeros are permitted but not required.
- %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 week number of the year (Sunday as the first day of the
week) using the locale's alternative numeric symbols.
- %Ow
- The number of the weekday (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 (offset from %C) using the locale's alternative
numeric symbols.
The broken-down time structure
tm is defined in
<time.h> as
follows:
struct tm {
int tm_sec; /* seconds */
int tm_min; /* minutes */
int tm_hour; /* hours */
int tm_mday; /* day of the month */
int tm_mon; /* month */
int tm_year; /* year */
int tm_wday; /* day of the week */
int tm_yday; /* day in the year */
int tm_isdst; /* daylight saving time */
};
The return value of the function is a pointer to the first character not
processed in this function call. In case the input string contains more
characters than required by the format string the return value points right
after the last consumed input character. In case the whole input string is
consumed the return value points to the NUL byte at the end of the string. If
strptime() fails to match all of the format string and therefore an
error occurred the function returns
NULL.
XPG4, SUSv2, POSIX 1003.1-2001.
The following example demonstrates the use of
strptime() and
strftime().
#include <stdio.h>
#include <time.h>
int main() {
struct tm tm;
char buf[255];
strptime("2001-11-12 18:31:01", "%Y-%m-%d %H:%M:%S", &tm);
strftime(buf, sizeof(buf), "%d %b %Y %H:%M", &tm);
puts(buf);
return 0;
}
For reasons of symmetry, glibc tries to support for
strptime the same
format characters as for
strftime. (In most cases the corresponding
fields are parsed, but no field in
tm is changed.) This leads to
- %F
- Equivalent to %Y-%m-%d, the ISO 8601 date
format.
- %g
- The year corresponding to the ISO week number, but without
the century (0-99).
- %G
- The year corresponding to the ISO week number. (For
example, 1991.)
- %u
- The day of the week as a decimal number (1-7, where Monday
= 1).
- %V
- The ISO 8601:1988 week number as a decimal number (1-53).
If the week (starting on Monday) containing 1 January has four or more
days in the new year, then it is considered week 1. Otherwise, it is the
last week of the previous year, and the next week is week 1.
- %z
- An RFC-822/ISO 8601 standard time zone specification.
- %Z
- The timezone name.
Similarly, because of GNU extensions to
strftime, %k is accepted as a
synonym for %H, and %l should be accepted as a synonym for %I, and %P is
accepted as a synonym for %p. Finally
- %s
- The number of seconds since the epoch, i.e., since
1970-01-01 00:00:00 UTC. Leap seconds are not counted unless leap second
support is available.
The GNU libc implementation does not require whitespace between two field
descriptors.
In principle, this function does not initialize
tm but only stores the
values specified. This means that
tm should be initialized before the
call. Details differ a bit between different Unix systems. The GNU libc
implementation does not touch those fields which are not explicitly specified,
except that it recomputes the
tm_wday and
tm_yday field if any
of the year, month, or day elements changed.
This function is available since libc 4.6.8. Linux libc4 and libc5 includes
define the prototype unconditionally; glibc2 includes provide a prototype only
when _XOPEN_SOURCE or _GNU_SOURCE are defined.
Before libc 5.4.13 whitespace (and the 'n' and 't' specifications) was not
handled, no 'E' and 'O' locale modifier characters were accepted, and the 'C'
specification was a synonym for the 'c' specification.
The 'y' (year in century) specification is taken to specify a year in the 20th
century by libc4 and libc5. It is taken to be a year in the range 1950-2049 by
glibc 2.0. It is taken to be a year in 1969-2068 since glibc 2.1.
time(2),
getdate(3),
scanf(3),
setlocale(3),
strftime(3)
