clock(n) Tcl Built-In Commands clock(n)_________________________________________________________________NAMEclock - Obtain and manipulate time
SYNOPSISclock 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
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 resolu-
tion 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).
%I Hour in 12-hour format (00 - 12).
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clock(n) Tcl Built-In Commands clock(n)
%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 Win-
dows):
%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 for-
mat 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
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clock(n) Tcl Built-In Commands clock(n)
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 speci-
fied 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 specifica-
tions 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 speci-
fied, hh is interpreted on a 24-hour clock.
date A specific month and day with optional year.
The acceptable formats are mm/dd?/yy?, mon-
thname dd ?, yy?, dd monthname ?yy? and day,
dd monthname yy. The default year is the
current year. If the year is less then 100,
then 1900 is added to it.
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 fol-
lowing 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 pro-
duced after allowing for daylight savings time
Tcl 7.4 3
clock(n) Tcl Built-In Commands clock(n)
differences.
clock seconds
Return the current date and time as a system-depen-
dent integer value. The unit of the value is sec-
onds, allowing it to be used for relative time cal-
culations. 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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