Tcl Built-In Commands clock(1T)
NAME
clock - Obtain and manipulate time
SYNOPSIS
clock option ?arg arg ...?
DESCRIPTION
This command performs one of several operations that may
obtain or manipulate strings or values that represent some
notion of time. The option argument determines what action
is carried out by the command. The legal options (which may
be abbreviated) are:
clock clicks ?-milliseconds?
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. If -milliseconds is specified, then the value
is guaranteed to be of millisecond granularity. This
value should only be used for the relative measurement
of elapsed time.
clock format clockValue ?-format string? ?-gmt boolean?
Converts an integer time value, typically returned by
clock seconds, clock scan, or the atime or mtime
options of the file command, to human-readable form.
If the -format 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 % followed
by a field descriptor character. All other characters
are copied into the result. Valid field descriptors
are:
%% Insert a %.
%a Abbreviated weekday name (Mon, Tue, etc.).
%A Full weekday name (Monday, Tuesday, etc.).
%b Abbreviated month name (Jan, Feb, etc.).
%B Full month name.
%c
Locale specific date and time. The format for
date and time in the default "C" locale on
Unix/Mac is "%a %b %d %H:%M:%S %Y". On Windows,
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Tcl Built-In Commands clock(1T)
this value is the locale specific long date and
time, as specified in the Regional Options control
panel settings.
%C
First two digits of the four-digit year (19 or
20).
%d Day of month (01 - 31).
%D
Date as %m/%d/%y.
%e
Day of month (1 - 31), no leading zeros.
%g
The ISO8601 year number corresponding to the
ISO8601 week (%V), expressed as a two-digit year-
of-the-century, with leading zero if necessary.
%G
The ISO8601 year number corresponding to the
ISO8601 week (%V), expressed as a four-digit
number.
%h
Abbreviated month name.
%H Hour in 24-hour format (00 - 23).
%I
Hour in 12-hour format (01 - 12).
%j Day of year (001 - 366).
%k
Hour in 24-hour format, without leading zeros (0 -
23).
%l
Hour in 12-hour format, without leading zeros (1 -
12).
%m Month number (01 - 12).
%M Minute (00 - 59).
%n
Insert a newline.
%p AM/PM indicator.
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Tcl Built-In Commands clock(1T)
%r
Time in a locale-specific "meridian" format. The
"meridian" format in the default "C" locale is
"%I:%M:%S %p".
%R
Time as %H:%M.
%s
Count of seconds since the epoch, expressed as a
decimal integer.
%S Seconds (00 - 59).
%t
Insert a tab.
%T
Time as %H:%M:%S.
%u
Weekday number (Monday = 1, Sunday = 7).
%U Week of year (00 - 52), Sunday is the first day of
the week.
%V
Week of year according to ISO-8601 rules. Week 1
of a given year is the week containing 4 January.
%w
Weekday number (Sunday = 0, Saturday = 6).
%W Week of year (00 - 52), Monday is the first day of
the week.
%x
Locale specific date format. The format for a
date in the default "C" locale for Unix/Mac is
"%m/%d/%y". On Windows, this value is the locale
specific short date format, as specified in the
Regional Options control panel settings.
%X
Locale specific 24-hour time format. The format
for a 24-hour time in the default "C" locale for
Unix/Mac is "%H:%M:%S". On Windows, this value is
the locale specific time format, as specified in
the Regional Options control panel settings.
%y Year without century (00 - 99).
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Tcl Built-In Commands clock(1T)
%Y Year with century (e.g. 1990)
%Z Time zone name.
If the -format argument is not specified, the format
string "%a %b %d %H:%M:%S %Z %Y" is used. If the -gmt
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.
clock scan dateString ?-base clockVal? ?-gmt boolean?
Convert dateString to an integer clock value (see clock
seconds). 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 speci-
fied, the current date is assumed. If the string does
not contain a time zone mnemonic, the local time zone
is assumed, unless the -gmt argument is true, in which
case the clock value is calculated assuming that the
specified time is relative to Greenwich Mean Time. -
gmt, if specified, affects only the computed time
value; it does not impact the interpretation of -base.
If the -base 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.
The dateString consists of zero or more specifications
of the following form:
time A time of day, which is of the form: hh?:mm?:ss??
?meridian? ?zone? or hhmm ?meridian? ?zone?. If no
meridian is specified, hh is interpreted on a 24-
hour clock.
date A specific month and day with optional year. The
acceptable formats are mm/dd?/yy?, monthname dd ?,
yy?, dd monthname ?yy?, day, dd monthname yy,
?C?yymmdd, ?C?yy-mm-dd, dd-monthname-?C?yy.
The default year is the current year. If the year
is less 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.
ISO 8601 point-in-time
An ISO 8601 point-in-time specification, such as
CyymmddThhmmss, where T is the literal T,
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Tcl Built-In Commands clock(1T)
Cyymmdd hhmmss, or CyymmddThh:mm:ss. Note that
only these three formats are accepted. The com-
mand does not accept the full range of point-in-
time specifications specified in ISO8601. Other
formats can be recognized by using commands such
as regexp to extract their fields and reorganize
them into a form accepted by the clock scan com-
mand.
relative time
A specification relative to the current time. The
format is number unit acceptable units are year,
fortnight, month, week, day, hour, minute (or
min), and second (or sec). The unit can be speci-
fied as a singular or plural, as in 3 weeks.
These modifiers may also be specified: tomorrow,
yesterday, today, now, last, this, next, ago.
The actual date is calculated according to the follow-
ing 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 speci-
fied, and no absolute or relative time is given, mid-
night 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.
Daylight savings time correction is applied only when
the relative time is specified in units of days or
more, ie, days, weeks, fortnights, months or years.
This means that when crossing the daylight savings time
boundary, different results will be given for clock
scan "1 day" and clock scan "24 hours":
% clock scan "1 day" -base [clock scan 1999-10-31]
941443200
% clock scan "24 hours" -base [clock scan 1999-10-31]
941439600
clock seconds
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.
SEE ALSO
date(1), time(1T)
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Tcl Built-In Commands clock(1T)
KEYWORDS
clock, date, time
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Availability SUNWTcl
Interface Stability Uncommitted
NOTES
Source for Tcl is available on http:/opensolaris.org.
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