clock(n) Tcl (7.4) clock(n)
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NAME
clock - Obtain and manipulate time
SYNOPSIS
clock option ?arg arg ...?
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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
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.
clock format clockValue ?-format string? ?-gmt boolean?
Converts an integer time value, typically returned by
clock seconds, clock scan, or the atime, mtime, or
ctime 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.
%d Day of month (01 - 31).
%H Hour in 24-hour format (00 - 23).
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clock(n) Tcl (7.4) clock(n)
%I Hour in 12-hour format (00 - 12).
%j Day of year (001 - 366).
%m Month number (01 - 12).
%M Minute (00 - 59).
%p AM/PM indicator.
%S Seconds (00 - 59).
%U Week of year (01 - 52), Sunday is the first day of
the week.
%w Weekday number (Sunday = 0).
%W Week of year (01 - 52), Monday is the first day of
the week.
%x Locale specific date format.
%X Locale specific time format.
%y Year without century (00 - 99).
%Y Year with century (e.g. 1990)
%Z Time zone name.
In addition, the following field descriptors may be
supported on some systems (e.g. Unix but not Windows):
%D Date as %m/%d/%y.
%e Day of month (1 - 31), no leading zeros.
%h Abbreviated month name.
%n Insert a newline.
%r Time as %I:%M:%S %p.
%R Time as %H:%M.
%t Insert a tab.
%T Time as %H:%M:%S.
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
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clock(n) Tcl (7.4) clock(n)
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
specified, 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.
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? and day, dd monthname 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.
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
specified 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
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,
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clock(n) Tcl (7.4) clock(n)
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.
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.
KEYWORDS
clock, date, time
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