shell_cmds-55.tar.gz

[apple/shell_cmds.git] / date / date.1

.\"	$NetBSD: date.1,v 1.22 1998/06/08 09:07:13 lukem Exp $
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.\"     @(#)date.1	8.3 (Berkeley) 4/28/95
.\"
.Dd January 20, 1998
.Dt DATE 1
.Os
.Sh NAME
.Nm date
.Nd display or set date and time
.Sh SYNOPSIS
.Nm
.Op Fl nu
.Op Fl r Ar seconds
.Op Cm + Ns Ar format
.Nm ""
.Ar [[[[[cc]yy]mm]dd]hh]mm[\&.ss]
.Sh DESCRIPTION
.Nm
displays the current date and time when invoked without arguments.
Providing arguments will format the date and time in a user-defined
way or set the date.
Only the superuser may set the date.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl n
The utility
.Xr timed 8
is used to synchronize the clocks on groups of machines.
By default, if
timed
is running,
.Nm
will set the time on all of the machines in the local group.
The
.Fl n
option stops
.Nm
from setting the time for other than the current machine.
.It Fl r
Print out the date and time that is
.Ar seconds
from the Epoch.
.It Fl u
Display or set the date in
.Tn UTC
(universal) time.
.El
.Pp
An operand with a leading plus (``+'') sign signals a user-defined format
string which specifies the format in which to display the date and time.
The format string may contain any of the conversion specifications described
in the 
.Xr strftime 3
manual page, as well as any arbitrary text.
A <newline> character is always output after the characters specified by
the format string.
The format string for the default display is:
.Bd -literal -offset indent
``%a %b %e %H:%M:%S %Z %Y''.
.Ed
.Pp
If an operand does not have a leading plus sign, it is interpreted as
a value for setting the system's notion of the current date and time.
The canonical representation for setting the date and time is:
.Pp
.Bl -tag -width Ds -compact -offset indent
.It Ar cc
The first two digits of the year (the century).
.It Ar yy
The second two digits of the year.  If
.Dq yy
is specified, but
.Dq cc
is not, a value for
.Dq yy
between 69 and 99 results in a
.Dq cc
value of 19.  Otherwise, a
.Dq cc
value of 20 is used.
.It Ar mm
The month of the year, from 1 to 12.
.It Ar dd
The day of the month, from 1 to 31.
.It Ar hh
The hour of the day, from 0 to 23.
.It Ar mm
The minute of the hour, from 0 to 59.
.It Ar ss
The second of the minute, from 0 to 61.
.El
.Pp
Everything but the minutes is optional.
.Pp
Time changes for Daylight Saving and Standard time and leap seconds
and years are handled automatically.
.Sh EXAMPLES
The command:
.Bd -literal -offset indent
date "+DATE: %m/%d/%y%nTIME: %H:%M:%S"
.Ed
.Pp
will display:
.Bd -literal -offset indent
DATE: 11/21/87
TIME: 13:36:16
.Ed
.Pp
The command:
.Bd -literal -offset indent
date 8506131627
.Ed
.Pp
sets the date to
.Dq Li "June 13, 1985, 4:27 PM" .
.Pp
The command:
.Bd -literal -offset indent
date 1432
.Ed
.Pp
sets the time to
.Li "2:32 PM" ,
without modifying the date.
.Sh ENVIRONMENT VARIABLES
The following environment variables affect the execution of
.Nm
:
.Bl -tag -width TZ
.It Ev TZ
The timezone to use when displaying dates.
See
.Xr environ 7
for more information.
.El
.Sh FILES
.Bl -tag -width /var/log/messages -compact
.It Pa /var/log/wtmp
A record of date resets and time changes.
.It Pa /var/log/messages
A record of the user setting the time.
.El
.Sh SEE ALSO
.Xr gettimeofday 2 ,
.Xr strftime 3 ,
.Xr utmp 5 ,
.Xr timed 8
.Rs
.%T "TSP: The Time Synchronization Protocol for UNIX 4.3BSD"
.%A R. Gusella
.%A S. Zatti
.Re
.Sh DIAGNOSTICS
Exit status is 0 on success, 1 if unable to set the date, and 2
if able to set the local date, but unable to set it globally.
.Pp
Occasionally, when
.Xr timed 8
synchronizes the time on many hosts, the setting of a new time value may
require more than a few seconds.
On these occasions,
.Nm
prints:
.Ql Network time being set .
The message
.Ql Communication error with timed
occurs when the communication
between
.Nm
and
timed
fails.
.Sh STANDARDS
The
.Nm
utility is expected to be compatible with
.St -p1003.2 .