Libc-763.11.tar.gz

[apple/libc.git] / stdtime / strptime.3

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.\" $FreeBSD: src/lib/libc/stdtime/strptime.3,v 1.24 2005/01/20 09:17:04 ru Exp $
.\" "
.Dd January 4, 2003
.Dt STRPTIME 3
.Os
.Sh NAME
.Nm strptime ,
.Nm strptime_l
.Nd parse date and time string
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In time.h
.Ft char *
.Fo strptime
.Fa "const char *restrict buf"
.Fa "const char *restrict format"
.Fa "struct tm *restrict tm"
.Fc
.In time.h
.In xlocale.h
.Ft char *
.Fo strptime_l
.Fa "const char *restrict buf"
.Fa "const char *restrict format"
.Fa "struct tm *restrict tm"
.Fa "locale_t loc"
.Fc
.Sh DESCRIPTION
The
.Fn strptime
function parses the string in the buffer
.Fa buf ,
according to the string pointed to by
.Fa format ,
and fills in the elements of the structure pointed to by
.Fa tm .
The resulting values will be relative to the local time zone.
Thus, it can be considered the reverse operation of
.Xr strftime 3 .
.Pp
The
.Fa 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
.Xr strftime 3 .
.Pp
Two-digit year values, including formats
.Fa %y
and
.Fa \&%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).
.Pp
If the
.Fa format
string does not contain enough conversion specifications to completely
specify the resulting
.Vt struct tm ,
the unspecified members of
.Va tm
are left untouched.
For example, if
.Fa format
is
.Dq Li "%H:%M:%S" ,
only
.Va tm_hour ,
.Va tm_sec
and
.Va tm_min
will be modified.
If time relative to today is desired, initialize the
.Fa tm
structure with today's date before passing it to
.Fn strptime .
.Pp
While the
.Fn strptime
function uses the current locale, the
.Fn strptime_l
function may be passed a locale directly. See
.Xr xlocale 3
for more information.
.Sh RETURN VALUES
Upon successful completion,
.Fn strptime
returns the pointer to the first character in
.Fa buf
that has not been required to satisfy the specified conversions in
.Fa format .
It returns
.Dv NULL
if one of the conversions failed.
.Sh LEGACY DESCRIPTION
In legacy mode, the
.Fa %Y
format specifier expects exactly 4 digits (leaving any trailing digits for the
next specifier).
.Sh SEE ALSO
.Xr date 1 ,
.Xr scanf 3 ,
.Xr strftime 3 ,
.Xr xlocale 3
.Sh HISTORY
The
.Fn strptime
function appeared in
.Fx 3.0 .
.Sh AUTHORS
The
.Fn strptime
function has been contributed by Powerdog Industries.
.Pp
This man page was written by
.An J\(:org Wunsch .
.Sh BUGS
Both the
.Fa %e
and
.Fa %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.
.Pp
The
.Fa %p
format specifier has no effect unless it is parsed
.Em after
hour-related specifiers.
Specifying
.Fa %l
without
.Fa %p
will produce undefined results.
Note that 12AM
(ante meridiem)
is taken as midnight
and 12PM
(post meridiem)
is taken as noon.
.Pp
The
.Fa %U
and
.Fa %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).
.Pp
The
.Fa %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
.Fa EST
which is both Eastern Standard Time and Eastern Australia Summer Time.
.Pp
The
.Fn strptime
function does not correctly handle multibyte characters in the
.Fa format
argument.