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'\"

'\" Copyright (c) 1992-1995 Karl Lehenbauer and Mark Diekhans.

'\" Copyright (c) 1995-1997 Sun Microsystems, Inc.

'\"

'\" This documentation is derived from the time and date facilities of

'\" TclX, by Mark Diekhans and Karl Lehenbauer.

'\"

'\" See the file "license.terms" for information on usage and redistribution

'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.

'\"

'\" RCS: @(#) $Id: clock.n,v 1.1.1.1 2002-01-16 10:25:24 markom Exp $

'\"

.so man.macros

.TH clock n 7.4 Tcl "Tcl Built-In Commands"

.BS

'\" Note:  do not modify the .SH NAME line immediately below!

.SH NAME

clock \- Obtain and manipulate time

.SH SYNOPSIS

\fBclock \fIoption\fR ?\fIarg arg ...\fR?

.BE

.SH DESCRIPTION

.PP

This command performs one of several operations that may obtain

or manipulate strings or values that represent some notion of

time.  The \fIoption\fR argument determines what action is carried

out by the command.  The legal \fIoptions\fR (which may be

abbreviated) are:

.TP

\fBclock clicks\fR

Return a high-resolution time value as a system-dependent integer

value.  The unit of the value is system-dependent but should be the

highest resolution clock available on the system such as a CPU cycle

counter. This value should only be used for the relative measurement

of elapsed time.

.TP

\fBclock format \fIclockValue\fR ?\fB\-format \fIstring\fR? ?\fB\-gmt \fIboolean\fR?

Converts an integer time value, typically returned by

\fBclock seconds\fR, \fBclock scan\fR, or the \fBatime\fR, \fBmtime\fR,

or \fBctime\fR options of the \fBfile\fR command, to human-readable

form.  If the \fB\-format\fR argument is present the next argument is a

string that describes how the date and time are to be formatted.

Field descriptors consist of a \fB%\fR followed by a field

descriptor character.  All other characters are copied into the result.

Valid field descriptors are:

.RS

.IP \fB%%\fR

Insert a %.

.IP \fB%a\fR

Abbreviated weekday name (Mon, Tue, etc.).

.IP \fB%A\fR

Full weekday name (Monday, Tuesday, etc.).

.IP \fB%b\fR

Abbreviated month name (Jan, Feb, etc.).

.IP \fB%B\fR

Full month name.

.IP \fB%c\fR

Locale specific date and time.

.IP \fB%d\fR

Day of month (01 - 31).

.IP \fB%H\fR

Hour in 24-hour format (00 - 23).

.IP \fB%I\fR

Hour in 12-hour format (00 - 12).

.IP \fB%j\fR

Day of year (001 - 366).

.IP \fB%m\fR

Month number (01 - 12).

.IP \fB%M\fR

Minute (00 - 59).

.IP \fB%p\fR

AM/PM indicator.

.IP \fB%S\fR

Seconds (00 - 59).

.IP \fB%U\fR

Week of year (01 - 52), Sunday is the first day of the week.

.IP \fB%w\fR

Weekday number (Sunday = 0).

.IP \fB%W\fR

Week of year (01 - 52), Monday is the first day of the week.

.IP \fB%x\fR

Locale specific date format.

.IP \fB%X\fR

Locale specific time format.

.IP \fB%y\fR

Year without century (00 - 99).

.IP \fB%Y\fR

Year with century (e.g. 1990)

.IP \fB%Z\fR

Time zone name.

.RE

.sp

.RS

In addition, the following field descriptors may be supported on some

systems (e.g. Unix but not Windows):

.IP \fB%D\fR

Date as %m/%d/%y.

.IP \fB%e\fR

Day of month (1 - 31), no leading zeros.

.IP \fB%h\fR

Abbreviated month name.

.IP \fB%n\fR

Insert a newline.

.IP \fB%r\fR

Time as %I:%M:%S %p.

.IP \fB%R\fR

Time as %H:%M.

.IP \fB%t\fR

Insert a tab.

.IP \fB%T\fR

Time as %H:%M:%S.

.RE

.sp

.RS

If the \fB\-format\fR argument is not specified, the format string

"\fB%a %b %d %H:%M:%S %Z %Y\fR" is used.  If the \fB\-gmt\fR argument

is present the next argument must be a boolean which if true specifies

that the time will be formatted as Greenwich Mean Time. If false

then the local timezone will be used as defined by the operating

environment.

.RE

.TP

\fBclock scan \fIdateString\fR ?\fB\-base \fIclockVal\fR? ?\fB\-gmt \fIboolean\fR?

Convert \fIdateString\fR to an integer clock value (see \fBclock seconds\fR).

This command can parse and convert virtually any standard date and/or time

string, which can include standard time zone mnemonics.  If only a time is

specified, the current date is assumed.  If the string does not contain a

time zone mnemonic, the local time zone is assumed, unless the \fB\-gmt\fR

argument is true, in which case the clock value is calculated assuming

that the specified time is relative to Greenwich Mean Time.

.sp

If the \fB\-base\fR flag is specified, the next argument should contain

an integer clock value.  Only the date in this value is used, not the

time.  This is useful for determining the time on a specific day or

doing other date-relative conversions.

.sp

The \fIdateString\fR consists of zero or more specifications of the

following form:

.RS

.TP

\fItime\fR

A time of day, which is of the form: \fIhh\fR?\fI:mm\fR?\fI:ss\fR??

?\fImeridian\fR? ?\fIzone\fR? or \fIhhmm \fR?\fImeridian\fR?

?\fIzone\fR?. If no meridian is specified, \fIhh\fR is interpreted on

a 24-hour clock.

.TP

\fIdate\fR

A specific month and day with optional year.  The

acceptable formats are \fImm/dd\fR?\fI/yy\fR?, \fImonthname dd\fR

?, \fIyy\fR?, \fIdd monthname \fR?\fIyy\fR? and \fIday, dd monthname

yy\fR.  The default year is the current year.  If the year is less

.VS

than 100, we treat the years 00-68 as 2000-2068 and the years 69-99

as 1969-1999.  Not all platforms can represent the years 38-70, so

an error may result if these years are used.

.VE

.TP

\fIrelative time\fR

A specification relative to the current time.  The format is \fInumber

unit\fR acceptable units are \fByear\fR, \fBfortnight\fR, \fBmonth\fR, \fBweek\fR, \fBday\fR,

\fBhour\fR, \fBminute\fR (or \fBmin\fR), and \fBsecond\fR (or \fBsec\fR).  The

unit can be specified as a singular or plural, as in \fB3 weeks\fR.

These modifiers may also be specified:

\fBtomorrow\fR, \fByesterday\fR, \fBtoday\fR, \fBnow\fR,

\fBlast\fR, \fBthis\fR, \fBnext\fR, \fBago\fR.

.RE

.sp

.RS

The actual date is calculated according to the following steps.

First, any absolute date and/or time is processed and converted.

Using that time as the base, day-of-week specifications are added.

Next, relative specifications are used.  If a date or day is

specified, and no absolute or relative time is given, midnight is

used.  Finally, a correction is applied so that the correct hour of

the day is produced after allowing for daylight savings time

differences and the correct date is given when going from the end

of a long month to a short month.

.RE

.TP

\fBclock seconds\fR

Return the current date and time as a system-dependent integer value.  The

unit of the value is seconds, allowing it to be used for relative time

calculations.  The value is usually defined as total elapsed time from

an ``epoch''.  You shouldn't assume the value of the epoch.

.SH KEYWORDS

clock, date, time