strptime

strptime - convert a string representation of time to a time tm structure

R #define _XOPEN_SOURCE /* glibc2 needs this */
#include <time.h> I char *strptime(const char * s , const char * format , I struct tm * tm );

The R strptime () function is the converse function to strftime(3) and converts the character string pointed to by s to values which are stored in the tm structure pointed to by R tm , using the format specified by R 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 R 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.

%%

R %a or %A

R %b or %B or %h

%c

%C

R %d or %e

%D

R %H

R %I

%j

%m

%M

%n

%p

%r

%R

%S

%t

%T

%U

%w

%W

%x

%X

%y

%Y

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

%EC

%Ex

%EX

%Ey

%EY

The O modifier specifies that the numerical input may be in an alternative locale-dependent format:

R %Od or %Oe

%OH

%OI

%Om

%OM

%OS

%OU

%Ow

%OW

%Oy

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 null byte at the end of the string. If R strptime () fails to match all of the format string and therefore an error occurred the function returns NULL.

SUSv2, POSIX.1-2001.

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 R tm_wday and R 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.

Glibc Notes

For reasons of symmetry, glibc tries to support for R 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

%g

%G

%u

%V

%z

%Z

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 GNU libc implementation does not require whitespace between two field descriptors.

The following example demonstrates the use of R strptime () and strftime(3).

#include <stdio.h>
#include <time.h>

int
main(void)
{
    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);
    exit(EXIT_SUCCESS);
}

time(2), getdate(3), scanf(3), setlocale(3), strftime(3), feature_test_macros(7)