strptime - convert a string representation of time to a time tm structure
Standard C library (
libc,
-lc)
#define _XOPEN_SOURCE /* See feature_test_macros(7) */
#include <time.h>
char *strptime(const char *restrict s, const char *restrict format,
struct tm *restrict tm);
The
strptime() function is the converse of
strftime(3); it
converts the character string pointed to by
s to values which are
stored in the "broken-down time" structure pointed to by
tm,
using the format specified by
format.
The broken-down time structure
tm is described in
tm(3type).
The
format argument 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 the name of a day of the week or a 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 name of the day of the week 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 behavior
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 ordinal number of the day of the week (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 ordinal number of the day of the week (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 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 null 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.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
strptime () |
Thread safety |
MT-Safe env locale |
POSIX.1-2001, POSIX.1-2008, SUSv2.
In principle, this function does not initialize
tm but stores only the
values specified. This means that
tm should be initialized before the
call. Details differ a bit between different UNIX systems. The glibc
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.
The 'y' (year in century) specification is taken to specify 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.
For reasons of symmetry, glibc tries to support for
strptime() the same
format characters as for
strftime(3). (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 timezone specification.
- %Z
- The timezone name.
Similarly, because of GNU extensions to
strftime(3),
%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, 1970-01-01 00:00:00
+0000 (UTC). Leap seconds are not counted unless leap second support is
available.
The glibc implementation does not require whitespace between two field
descriptors.
The following example demonstrates the use of
strptime() and
strftime(3).
#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
int
main(void)
{
struct tm tm;
char buf[255];
memset(&tm, 0, sizeof(tm));
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);
exit(EXIT_SUCCESS);
}
time(2),
getdate(3),
scanf(3),
setlocale(3),
strftime(3)