strptime

Name

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

Library

libc.lib

Synopsis

#include <time.h>

char * strptime (const char *restrict buf, const char *restrict format, struct tm *restrict timeptr);

Return values

Upon successful completion, strptime returns the pointer to the first character in buf that has not been required to satisfy the specified conversions in format. It returns NULL if one of the conversions failed.

Detailed description

The strptime function parses the string in the buffer buf according to the string pointed to by format, and fills in the elements of the structure pointed to by timeptr. The resulting values will be relative to the local time zone. Thus, it can be considered the reverse operation of strftime.

The format string consists of zero or more conversion specifications and ordinary characters. All ordinary characters are matched exactly with the buffer, where white space in the format string will match any amount of white space in the buffer. All conversion specifications are identical to those described in strftime.

Two-digit year values, including formats %y and %D, are now interpreted as beginning at 1969 per POSIX requirements. Years 69-00 are interpreted in the 20th century (1969-2000), years 01-68 in the 21st century (2001-2068).

If the format string does not contain enough conversion specifications to completely specify the resulting struct tm , the unspecified members of timeptr are left untouched. For example, if format is "%H:%M:%S", only tm_hour, tm_sec and tm_min will be modified. If time relative to today is desired, initialize the timeptr structure with today’s date before passing it to strptime.

Examples

#include <string.h>
#include <stdio.h>
#include <time.h>
#include <locale.h>
int main()
{
    struct tm tm;
    char buf[255];
    char *locale;
    locale = setlocale(LC_TIME,"en_GB.ISO-8859-1");
    if( locale != NULL)
    {
       strptime("2001-11-12 18:31:01", "%Y-%m-%d %H:%M:%S", &tm);
       printf("sec = %d min = %d hours = %d \nYear = %d Month = %d day = %d\n",
       tm.tm_sec,tm.tm_min,tm.tm_hour,tm.tm_year,tm.tm_mon,tm.tm_mday);
       strftime(buf, sizeof(buf), "%d %B %Y %H:%M:%S", &tm);
       puts(buf);
       strptime("Mon","%a", &tm);
       strftime(buf, sizeof(buf), "%a", &tm);
       puts(buf);
    }
    else
    printf("Failed to set locale");
}

Output

sec = 1 min = 31 hours = 18
Year = 101 Month = 10 day = 12
12 November 2001 18:31:01
Mon

Bugs

Both the %e and %l format specifiers may incorrectly scan one too many digits if the intended values comprise only a single digit and that digit is followed immediately by another digit. Both specifiers accept zero-padded values, even though they are both defined as taking unpadded values.

The %p format specifier has no effect unless it is parsed after hour-related specifiers. Specifying %l without %p will produce undefined results. Note that 12AM (ante meridiem) is taken as midnight and 12PM (post meridiem) is taken as noon.

The %U and %W format specifiers accept any value within the range 00 to 53 without validating against other values supplied (like month or day of the year, for example).

The %Z format specifier only accepts time zone abbreviations of the local time zone, or the value "GMT". This limitation is because of ambiguity due to of the over loading of time zone abbreviations. One such example is EST which is both Eastern Standard Time and Eastern Australia Summer Time.

The strptime function does not correctly handle multibyte characters in the format argument.

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