libc/stdtime/strptime.3

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.Dd November 4, 2008
.Os
.Dt STRPTIME 3
.Sh NAME
.Nm strptime
.Nd converts a character string to a time value
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In time.h
.Ft char *
.Fn strptime "const char * restrict buf" "const char * restrict format" "struct tm * restrict tm"
.Sh DESCRIPTION
The
.Fn strptime
function converts the character string pointed to by
.Fa buf
to values which are stored in the
.Va tm
structure pointed to by
.Fa tm ,
using the format specified by
.Fa format .
.Pp
The
.Fa format
string consists of zero or more conversion specifications, whitespace
characters as defined by
.Fn isspace ,
and ordinary characters.
All ordinary characters in
.Fa format
are compared directly against the corresponding characters in
.Fa buf ;
comparisons which fail will cause
.Fn strptime
to fail.
Whitespace characters in
.Fa format
match any number of whitespace characters in
.Fa buf ,
including none.
.Pp
A conversion specification consists of a percent sign
.Ql %
followed by one
or two conversion characters which specify the replacement required.
There must be white-space or other non-alphanumeric characters between any
two conversion specifications.
.Pp
Conversion of alphanumeric strings (such as month and weekday names) is
done without regard to case.
Conversion specifications which cannot be matched will cause
.Fn strptime
to fail.
.Pp
The LC_TIME category defines the locale values for the conversion
specifications.
The following conversion specifications are supported:
.Bl -tag -width "xxxx"
.It Cm \&%a
the day of week, using the locale's weekday names;
either the abbreviated or full name may be specified.
.It Cm \&%A
the same as
.Cm \&%a .
.It Cm \&%b
the month, using the locale's month names;
either the abbreviated or full name may be specified.
.It Cm \&%B
the same as
.Cm \&%b .
.It Cm \&%c
the date and time, using the locale's date and time format.
.It Cm \&%C
the century number [0,99];
leading zeros are permitted but not required.
This conversion should be used in conjunction with the \&%y conversion.
.It Cm \&%d
the day of month [1,31];
leading zeros are permitted but not required.
.It Cm \&%D
the date as %m/%d/%y.
.It Cm \&%e
the same as
.Cm \&%d .
.It Cm \&%F
the date as %Y-%m-%d
(the ISO 8601 date format).
.It Cm \&%g
the year corresponding to the ISO week number, without the century.
.Po
A
.Nx
extension.
.Pc
.It Cm \&%G
the year corresponding to the ISO week number, with the century.
.Po
A
.Nx
extension.
.Pc
.It Cm \&%h
the same as
.Cm \&%b .
.It Cm \&%H
the hour (24-hour clock) [0,23];
leading zeros are permitted but not required.
.It Cm \&%I
the hour (12-hour clock) [1,12];
leading zeros are permitted but not required.
.It Cm \&%j
the day number of the year [1,366];
leading zeros are permitted but not required.
.It Cm \&%k
the same as
.Cm \&%H .
.It Cm \&%l
the same as
.Cm \&%I .
.It Cm \&%m
the month number [1,12];
leading zeros are permitted but not required.
.It Cm \&%M
the minute [0,59];
leading zeros are permitted but not required.
.It Cm \&%n
any white-space, including none.
.It Cm \&%p
the locale's equivalent of a.m. or p.m.
.It Cm \&%r
the time (12-hour clock) with %p, using the locale's time format.
.It Cm \&%R
the time as %H:%M.
.It Cm \&%S
the seconds [0,61];
leading zeros are permitted but not required.
.It Cm \&%t
any white-space, including none.
.It Cm \&%T
the time as %H:%M:%S.
.It Cm \&%u
the day of the week as a decimal number, where Monday = 1.
.Po
A
.Nx
extension.
.Pc
.It Cm \&%U
the week number of the year (Sunday as the first day of the week)
as a decimal number [0,53];
leading zeros are permitted but not required.
All days in a year preceding the first Sunday are considered to be in week 0.
.It Cm \&%V
the ISO 8601:1988 week number as a decimal number.
If the week (starting on Monday) that contains January 1 has more than
three days in the new year, then it is considered the first week of the
year.
If it has fewer than four days in the new year, then it is considered
the last week of the previous year.
Weeks are numbered from 1 to 53.
A
.Nx
extension.
.It Cm \&%w
the weekday as a decimal number [0,6], with 0 representing Sunday;
leading zeros are permitted but not required.
.It Cm \&%W
the week number of the year (Monday as the first day of the week)
as a decimal number [0,53];
leading zeros are permitted but not required.
All days in a year preceding the first Monday are considered to be in week 0.
.It Cm \&%x
the date, using the locale's date format.
.It Cm \&%X
the time, using the locale's time format.
.It Cm \&%y
the year within the 20th century [69,99] or the 21st century [0,68];
leading zeros are permitted but not required.
If specified in conjunction
with \&%C, specifies the year [0,99] within that century.
.It Cm \&%Y
the year, including the century (i.e., 1996).
.It Cm \&%z
an ISO 8601 timezone specification.
This is either,
.Dq Z
for
.Ql UTC ,
or the offset specified as:
.Dq [+-]hhmm
or
.Dq [+-]hh:mm
or
.Dq [+-]hh .
.Po
A
.Nx
extension.
.Pc
.It Cm \&%Z
timezone name or no characters when time zone information is unavailable.
.Po
A
.Nx
extension.
.Pc
.It Cm \&%%
matches a literal `%'.
No argument is converted.
.El
.Ss Modified conversion specifications
For compatibility, certain conversion specifications can be modified
by the
.Cm E
and
.Cm O
modifier characters to indicate that an alternative format or specification
should be used rather than the one normally used by the unmodified
conversion specification.
As there are currently neither alternative formats
nor specifications supported by the system, the behavior will be as if the
unmodified conversion specification were used.
.Pp
Case is ignored when matching string items in
.Fa buf ,
such as month and weekday names.
.Sh RETURN VALUES
If successful, the
.Fn strptime
function returns a pointer to the character following the last character
parsed.
Otherwise, a null pointer is returned.
.Sh SEE ALSO
.Xr ctime 3 ,
.Xr isspace 3 ,
.Xr localtime 3 ,
.Xr strftime 3
.Sh STANDARDS
The
.Fn strptime
function conforms to
.St -xpg4 .
.Sh BUGS
The
.Cm \&%Z
format specifier only accepts timezone
abbreviations of the local timezone,
or the value
.Dq GMT .
This limitation is caused by the ambiguity
of overloaded timezone abbreviations,
for example EST is both Eastern Standard
Time and Eastern Australia Summer Time.