path: root/lib/libc/time/strptime.3

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.Dd $Mdocdate: September 16 2011 $
.Dt STRPTIME 3
.Os
.Sh NAME
.Nm strptime
.Nd converts a character string to a time value
.Sh SYNOPSIS
.Fd #include <time.h>
.Ft char *
.Fn strptime "const char *buf" "const char *format" "struct tm *tm"
.Sh DESCRIPTION
The
.Nm
function converts the character string pointed to by
.Fa buf
to values which are stored in the ``tm'' structure pointed to by
.Fa tm ,
using the format specified by
.Fa format .
.Pp
The
.Fa format
string consists of zero or more directives.
A directive is composed of either one or more whitespace characters as
defined by
.Xr isspace 3 ,
an ordinary character (neither
.Sq %
nor a whitespace), or a conversion
specification.
A conversion specification consists of a percent sign
.Pq Sq %
followed by one or two conversion characters which specify the
replacement required.
There must be whitespace or other
non-alphanumeric characters between any two conversion specifications.
.Pp
The
.Dv 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.
Note that the converted value is added to the current value of the
``tm_year'' field (in order that the "\&%y" conversion be useful).
.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
.St -iso8601-4
date format).
.It Cm \&%g
the year corresponding to the ISO week number, without the century.
.It Cm \&%G
the year corresponding to the ISO week number, with the century.
.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 whitespace.
.It Cm \&%p
the locale's equivalent of
.Dq AM
or
.Dq PM .
.It Cm \&%r
the time as %I:%M:%S %p.
.It Cm \&%R
the time as %H:%M.
.It Cm \&%S
the seconds [0,60];
leading zeros are permitted but not required.
.It Cm \&%t
any whitespace.
.It Cm \&%T
the time as %H:%M:%S.
.It Cm \&%u
the day of the week as a decimal number, where Monday = 1.
.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
.St -iso8601-4
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.
.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 current century.
When a century is not otherwise
specified, values in the range 69\-99 refer to years in the twentieth
century (1969 to 1999 inclusive); values in the range 00\-68 refer
to years in the twenty-first century (2000 to 2068 inclusive).
Leading zeros are permitted but not required.
.It Cm \&%Y
the year, including the century (i.e., 1998).
.It Cm \&%z
an
.St -iso8601-4
or RFC 2822 timezone specification.
This is one of the following:
the offset from
Coordinated Universal Time
.Pq Ql UTC
specified as:
.Dq [+-]hhmm ,
.Dq [+-]hh:mm ,
or
.Dq [+-]hh ;
.Ql UTC
specified as:
.Dq GMT
.Pq Ql Greenwich Mean Time ,
.Dq UT
.Pq Ql Universal Time ,
or
.Dq Z
.Pq Ql Zulu Time ;
a three character US timezone specified as:
.Dq EDT ,
.Dq EST ,
.Dq CDT ,
.Dq CST ,
.Dq MDT ,
.Dq MST ,
.Dq PDT ,
or
.Dq PST ,
with the first letter standing for
.Ql Eastern
.Pq Dq E ,
.Ql Central
.Pq Dq C ,
.Ql Mountain
.Pq Dq M
or
.Ql Pacific
.Pq Dq P ,
and the second letter standing for
.Ql Daylight
.Po
.Dq D
or summer
.Pc
time
or
.Ql Standard
.Pq Dq S
time;
a single letter military timezone specified as:
.Dq A
through
.Dq I
and
.Dq K
through
.Dq Y .
.It Cm \&%Z
timezone name or no characters when timezone information is unavailable.
.It Cm \&%%
A `%' is read.
No argument is converted.
.El
.Pp
There is no way to specify whether Daylight Saving Time is in effect when
calling
.Nm .
To use the resulting
.Fa tm
structure with functions that check the
.Fa tm_isdst
field, either set it to a negative value, which will cause
.Xr mktime 3
to attempt to divine whether Daylight Saving Time would be in effect
for the given time, or compute the value manually.
.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
.Nm
function returns a pointer to the character following the last character
parsed.
Otherwise, a null pointer is returned.
.Sh SEE ALSO
.Xr mktime 3 ,
.Xr strftime 3
.Sh STANDARDS
The
.Fn strptime
function conforms to
.St -xpg4.2 .
.Pp
The
.Ql \&%G ,
.Ql \&%g ,
.Ql \&%u ,
.Ql \&%V ,
.Ql \&%Y ,
and
.Ql \&%Z
conversion specifications are extensions.
.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.