xref: /dflybsd-src/lib/libc/stdtime/getdate.3 (revision 8f9e67109499acc57ad368877f4b3b0b7cdf6d93)

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.Dd May 24, 2020
.Dt GETDATE 3
.Os
.Sh NAME
.Nm getdate ,
.Nm getdate_err
.Nd convert user format date and time
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In time.h
.Ft "struct tm *"
.Fo "getdate"
.Fa "const char *str"
.Fc
.Vt extern int getdate_err ;
.Sh DESCRIPTION
The
.Fn getdate
function converts a date or time character string pointed to by
.Fa str
into a static
.Vt tm
structure described in
.Xr tm 3 .
.Pp
The input string is parsed and interpreted using templates.
A text file containing templates is specified by the
environment variable
.Ev DATEMSK .
This should contain the full path to the template file.
Lines in the template file represent acceptable date and/or time
conversion specifications.
These specifications are similar to those given for
.Xr strptime 3 .
The first line in the template file that matches the input string
is used to interpret and convert to internal time format.
.Ss Internal Format Conversion
The following rules apply to converting the input into the internal format.
.Bl -bullet -offset indent
.It
If only the weekday is given, the conversion assumes today when the
weekday matches today or the first future matching weekday.
.It
If only the month and no year is given, the conversion assumes the
current month when the month matches or the first future matching month.
The first day of the month is assumed if no day is given.
.It
If only the year is given, the values of the
.Fa tm_mon ,
.Fa tm_mday ,
.Fa tm_wday ,
.Fa tm_yday ,
and
.Fa tm_isdst
members of the returned
.Vt "struct tm"
are unspecified.
.It
If the century is given, but the year within the century is not given,
the conversion assumes the current year.
.It
If no hour, minute, and second are given, the conversion assumes
the current hour, minute, and second.
.It
If no date is given, the conversion assumes today when the given hour
is greater than the current hour and tomorrow when the given hour is less.
.It
If
.Cm \&%Z
is being scanned, then the broken-down time is based on the
current time of the matched timezone and not the current runtime
environment timezone.
.El
.Sh RETURN VALUES
If successful, the
.Fn getdate
function returns a pointer to a static
.Vt tm
structure containing the broken-down time.
Otherwise, a null pointer is returned and
.Va getdate_err
is set to indicate the error.
.Pp
The variable
.Va getdate_err
can have the following values:
.Bl -tag -width NNN
.It 1
.Ev DATEMSK
environment variable is null or undefined.
.It 2
Cannot open the template file for reading.
.It 3
Get file status failed for template file.
.It 4
Template file is not a regular file.
.It 5
Encountered an error while reading the template file.
.It 6
Cannot allocate memory.
.It 7
Input string does not match any line in the template file.
.It 8
Input string is invalid (for example, February 31)
or could not be represented in a
.Vt time_t .
.El
.Sh ENVIRONMENT
.Bl -tag -width DATEMSK
.It Ev DATEMSK
The full path to the text file containing the templates
for acceptable date and/or time conversions.
.El
.Sh FILES
.Bl -tag -width DATEMSK
.It  Pa /usr/share/examples/getdate/datemsk.template
An example template file that could be specified via the
.Ev DATEMSK
environment variable.
.El
.Sh EXAMPLES
The following example shows the possible contents of a template file:
.Pp
.Bd -literal -offset indent -compact
%m
%A %B %d, %Y, %H:%M:%S
%A
%B
%m/%d/%y %I %p
%d,%m,%Y %H:%M
at %A the %dst of %B in %Y
run job at %I %p, %B %dnd
%A den %d. %B %Y %H.%M Uhr
.Ed
.Pp
The following are examples of valid input for the above template:
.Pp
.Bd -literal -offset indent -compact
10/1/87 4 PM
Friday
Friday September 18, 1987, 10:30:30
24,9,1986 10:30
at monday the 1st of december in 1986
run job at 3 PM, december 2nd
.Ed
.Pp
The following examples show how local data and time specification can be
defined in the template.
.Bl -column -offset indent ".Li Friday 12:00:00" ".Sy Line in Template"
.It Sy "Input String" Ta Sy "Line in Template"
.It Li 11/27/86 Ta Li \&%m/\&%d/\&%y
.It Li 27.11.86 Ta Li \&%d.\&%m.\&%y
.It Li 86-11-27 Ta Li \&%y-\&%m-\&%d
.It Li "Friday 12:00:00" Ta Li "\&%A \&%H:\&%M:\&%S"
.El
.Pp
The following examples illustrate the Internal Format Conversion rules
given that the current date is
.Li "Mon Sep 22 12:19:47 EDT 1986"
and the
.Ev LC_TIME
environment variable is set to the default C locale.
.Bl -column -offset indent ".Li Jan Wed 1989" ".Sy Line in Template" ".Sy Date"
.It Sy Input String Ta Sy Line in Template Ta Sy Date
.It Li Mon Ta Li \&%a Ta Li "Mon Sep 22 12:19:47 EDT 1986"
.It Li Sun Ta Li \&%a Ta Li "Sun Sep 28 12:19:47 EDT 1986"
.It Li Fri Ta Li \&%a Ta Li "Fri Sep 26 12:19:47 EDT 1986"
.It Li September Ta Li \&%B Ta Li "Mon Sep  1 12:19:47 EDT 1986"
.It Li January Ta Li \&%B Ta Li "Thu Jan  1 12:19:47 EST 1987"
.It Li December Ta Li \&%B Ta Li "Mon Dec  1 12:19:47 EST 1986"
.It Li "Sep Mon" Ta Li "\&%b %a" Ta Li "Mon Sep  1 12:19:47 EDT 1986"
.It Li "Jan Fri" Ta Li "\&%b %a" Ta Li "Fri Jan  2 12:19:47 EST 1987"
.It Li "Dec Mon" Ta Li "\&%b %a" Ta Li "Mon Dec  1 12:19:47 EST 1986"
.It Li "Jan Wed 1989" Ta Li "\&%b \&%a \&%Y" Ta Li "Wed Jan  4 12:19:47 EST 1989"
.It Li "Fri 9" Ta Li "\&%a \&%H" Ta Li "Fri Sep 26 09:00:00 EDT 1986"
.It Li "Feb 10:30" Ta Li "\&%b \&%H:\&%S" Ta Li "Sun Feb  1 10:00:30 EST 1987"
.It Li 10:30 Ta Li "\&%H:\&%M" Ta Li "Tue Sep 23 10:30:00 EDT 1986"
.It Li 13:30 Ta Li "\&%H:\&%M" Ta Li "Tue Sep 22 13:30:00 EDT 1986"
.El
.Sh SEE ALSO
.Xr ctime 3 ,
.Xr localtime 3 ,
.Xr mktime 3 ,
.Xr strftime 3 ,
.Xr strptime 3 ,
.Xr time 3
.Sh STANDARDS
The
.Fn getdate
function conforms to
.St -p1003.1-2001 .
.Sh HISTORY
The
.Nm
function appeared in
.At V.4 .
.Sh BUGS
The
.Nm
interface is inherently unsafe for multi-threaded programs or libraries,
since it returns a pointer to a static variable and uses a global state
variable.